#1 of 120
UHS 2024
Permalink
What is the percentage of H₂O in bone cells?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Tissue water content is inversely proportional to the requirement for physical rigidity.
Solution:- Most human soft tissues average ~70% water.
- However, bone cells (osteocytes) are encased in a dense, heavily calcified extracellular matrix designed for maximum rigid structural support.
- Because this matrix is heavily mineralized, the overall water content of living bone tissue is uniquely low, strictly maintained at roughly 20%.
Why other options are incorrect:- 70-60%: Represents standard soft cellular tissues (muscle, liver).
- 99%: Represents marine invertebrates like jellyfish.
#2 of 120
SZABMU 2024
Permalink
At 25 degrees Celsius, the concentration of each of \(H^+\) and \(OH^-\) ions in pure water is about ____ moles per liter.
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:The autoionization of water perfectly defines the neutral point of the pH scale.
Solution:- Water spontaneously, but rarely, dissociates into ions: $$ H_2O \rightleftharpoons H^+ + OH^- $$
- At standard room temperature (25°C), this dissociation reaches an exact thermodynamic equilibrium.
- Because one molecule of water yields exactly one \(H^+\) and one \(OH^-\), their concentrations must be perfectly equal to maintain neutrality.
- The measured concentration of each specific ion at this temperature is precisely \(10^{-7}\) moles per liter (which is why a neutral pH is mathematically 7: \(-log(10^{-7}) = 7\)).
Why other options are incorrect:- \(10^{-14}\): This is the ion product constant (\(K_w = [H^+][OH^-]\)), not the individual concentration of a single ion.
- \(10^{-6} / 10^{-12}\): Mathematically incorrect for neutral water at standard conditions.
#3 of 120
SZABMU 2024 Reconduct
Permalink
Which property of water helps to maintain the integrity of lipid bilayer membranes?
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Biological membranes are held together entirely by the thermodynamic avoidance of water.
Solution:- Water molecules bond intensely to one another via hydrogen bonds.
- When non-polar lipid tails are placed in water, they cannot form these bonds, forcing the water molecules to adopt a highly ordered, rigid, and energetically unfavorable "cage" around them.
- To minimize this unfavorable state, water physically forces the non-polar lipid tails to clump together, hiding them away in a bilayer core.
- This driving force, termed Hydrophobic exclusion, is the sole physical mechanism that maintains the structural integrity of every cell membrane.
Why other options are incorrect:- While Hydrogen bonding is the root cause, "Hydrophobic exclusion" is the specific, direct biochemical property/mechanism describing the membrane assembly process.
- Specific heat / Cohesion: Relate to thermal stability and capillary action, respectively.
#4 of 120
SZABMU 2024
Permalink
Which of the following monosaccharides is an aldehyde-hexose sugar?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Aldohexoses are six-carbon sugars with a terminal aldehyde functional group at Carbon-1.
Solution: Galactose (along with Glucose) is a classic aldohexose sugar (\(C_6H_{12}O_6\)). Fructose is a ketohexose, and Ribose is an aldopentose.
#5 of 120
SZABMU 2024
Permalink
Which of the following carbohydrates gives dark brown colour with iodine solution?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:The iodine test is a classic qualitative biochemical assay used to distinguish complex polysaccharides based on their helical coiling.
Solution:- When \(I_2\) interacts with the highly branched structure of Glycogen, the iodine molecules slip into the coils, producing a characteristic red-brown / dark brown color.
- This specifically differentiates it from plant starch.
Why other options are incorrect:- Starch: Produces a stark, intense blue-black color because its long amylose helices perfectly trap the iodine chains.
- Sucrose & Glucose: Small, simple sugars that lack the complex helical structure to trap iodine. They yield no color change (the solution remains the yellowish-brown color of raw iodine).
#6 of 120
NUMS 2024
Permalink
Less reactivity of sucrose is due to its:
A
High solubility in water
C
Unavailability of functional group
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Chemical reactivity in sugars is dictated by the availability of a free, unbonded anomeric carbon (the reducing end).
Solution:- To be a reactive "reducing sugar" (capable of reacting with Benedict's or Tollens' reagent), a sugar must have a free aldehyde or ketone group that can open up from the ring structure.
- In Sucrose, the highly reactive anomeric carbon of glucose (C1) is covalently bonded directly to the highly reactive anomeric carbon of fructose (C2).
- Because both functional groups are entirely locked up in this unique \(\alpha-1,2\) bond, the molecule has absolutely no free functional ends.
- This complete unavailability of functional groups makes sucrose non-reducing, highly stable, and exceptionally unreactive (perfect for safe transport in plant sap).
Why other options are incorrect:- 1-2 glycosidic linkage: While this is the cause of the unavailability, the direct chemical reason for the lack of reactivity itself is the literal "unavailability of the functional group". Both C and D are technically related, but C describes the fundamental chemical mechanism.
- High solubility / Polar nature: Physical properties unrelated to chemical redox reactivity.
#7 of 120
NUMS 2024
Permalink
Sucrose is used as a transport carbohydrate instead of glucose because:
B
It is non-reducing sugar
D
It does not change osmotic potential of water
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Plants must transport energy vast distances through the phloem without the sugar reacting with surrounding cellular structures along the way.
Solution:- Glucose contains a free, highly reactive aldehyde group (it is a reducing sugar). If plants pumped pure glucose through their veins, it would indiscriminately react with and damage transport proteins along the route.
- To solve this, plants bond glucose to fructose, locking both reactive ends together to form Sucrose.
- Because Sucrose is a completely stable, non-reducing sugar, it acts as a chemically inert "safe" cargo, traveling unharmed through the phloem until it reaches the root sinks where enzymes finally break it apart for use.
Why other options are incorrect:- Soluble in water: Both glucose and sucrose are highly soluble.
- Osmotic potential: All soluble sugars massively alter osmotic potential (which is actually how phloem sap physically flows).
- Is a disaccharide: Maltose is also a disaccharide, but it is highly reactive (reducing), so it is not used for transport. The key is being non-reducing.
#8 of 120
SZABMU 2024 Reconduct
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Percentage of glucose normally in human body is:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Blood glucose levels are strictly hormonally regulated to prevent osmotic shock and diabetic comas.
Solution:- The normal, healthy homeostatic concentration of fasting glucose in human blood is rigorously maintained between 80 to 120 mg per 100 mL of blood (dL).
- Mathematically, 80 mg (0.08 grams) per 100 mL of water (roughly 100 grams) equals exactly 0.08% by weight/volume.
- This tiny, highly regulated percentage provides constant energy without turning the blood into a thick, syrupy osmotic nightmare.
Why other options are incorrect:- Options like 8% or 1.8% would represent blood so thick with sugar it would immediately pull all water out of the brain cells via osmosis, causing instant death.
#9 of 120
SZABMU 2024 Reconduct
Permalink
Polysaccharide found most commonly in grains and seeds is:
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Plants require massive, insoluble energy reserves to fuel the germination of their offspring before they can grow leaves and photosynthesize.
Solution:- The universal energy storage polysaccharide of the entire plant kingdom is Starch.
- Plants pack massive quantities of starch granules into their grains (wheat, rice, corn) and seeds, ensuring the embryonic plant has a massive, slow-release energy source to rely on during early underground growth.
Why other options are incorrect:- Glycogen: The storage polysaccharide of animals (liver/muscle), never found in plants.
- Pectin: A structural gel-like carbohydrate found in the cell walls (makes jams set), not the primary bulk energy storage.
- Dextrin: A short, broken-down fragment of starch, not the naturally stored bulk molecule itself.
#10 of 120
SZABMU 2024 Reconduct
Permalink
Glycogen is most abundant in:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Animals utilize specific organs as bulk chemical warehouses to regulate systemic physiology.
Solution:- While skeletal muscles store glycogen strictly for their own selfish, localized use during sudden sprints, the Liver serves as the massive, altruistic glycogen reservoir for the entire body.
- Hepatocytes (Liver cells) can store up to 8-10% of their total mass as glycogen.
- When blood sugar drops, the liver rapidly breaks this glycogen down into free glucose and releases it into the blood to keep the brain alive. Therefore, by percentage weight, glycogen is most abundantly concentrated in the liver.
Why other options are incorrect:- Brain cells: Store virtually zero glycogen; they demand a constant, uninterrupted feed of glucose directly from the blood.
- Adipose cells: Store massive amounts of lipids (triglycerides), not carbohydrates.
- Smooth muscle: Has minor stores compared to the massive stockpiles in the liver and large skeletal muscles.
#11 of 120
SZABMU 2024 Reconduct
Permalink
Stereoisomers are molecules containing atoms are:
A
Same and bonded identically
B
Same and bonded dependently
C
Dependent and bonded identically
D
Dependent and bonded same
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Isomerism dictates how identical molecular formulas can yield completely different biological functions based on 3D geometry.
Solution:- Stereoisomers (spatial isomers) are molecules that have the exact same chemical formula and are exactly bonded identically in the same sequence (e.g., C-1 is bonded to C-2, which is bonded to C-3).
- Their only difference lies in how those identical bonds are oriented in three-dimensional space (e.g., an -OH group pointing "up" vs "down").
- A classic biological example is α-glucose vs β-glucose.
Why other options are incorrect:- Structural isomers (like glucose vs fructose) are bonded differently (the double bond is on a different carbon). Stereoisomers must be bonded identically, differing only in 3D geometry. The words "dependent" in the other options represent nonsensical distractor phrasing.
#12 of 120
KMU 2024
Permalink
Which is incorrect about the globular proteins?
A
Abundantly found in hair
C
Have polypeptide chains
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Proteins are sharply divided into functional (globular) and structural (fibrous) categories based entirely on their shape and solubility.
Solution:- We must identify the strictly false statement.
- Hair, nails, and outer skin are composed entirely of Keratin.
- Keratin is a tough, insoluble, extended fibrous protein designed to be rigid and waterproof.
- Therefore, stating that globular proteins are abundantly found in hair is completely incorrect.
Why other options are incorrect (they are TRUE statements):- Spherical in shape: True, the chains fold heavily inward into complex 3D globes (tertiary structure) to form active sites.
- Soluble in water: True, they hide their hydrophobic R-groups on the inside, exposing hydrophilic groups on the outside to dissolve in blood/cytoplasm (e.g., enzymes, antibodies).
- Have polypeptide chains: True, all proteins do.
#13 of 120
SZABMU 2024
Permalink
The bond between hydroxyl group of carboxylic group of one amino acid and hydrogen of amino group of second amino acid with release of water molecule is called?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:The primary structural backbone of all proteins is formed by a highly specific, repeating covalent linkage.
Solution:- When two amino acids approach each other, a condensation reaction occurs.
- The \(-OH\) is stripped from the carboxyl group of the first amino acid, and an \(-H\) is stripped from the amino group of the second.
- This expels a water molecule and forms a strong, covalent Carbon-Nitrogen bond specifically bridging the two monomers.
- In biochemistry, this specific C-N linkage between amino acids is exclusively called a Peptide bond.
Why other options are incorrect:- Glycosidic bond: Formed between two sugars, not amino acids.
- Disulfide bridge: Formed between the sulfur atoms of two distant Cysteine R-groups to stabilize 3D folding, not to link the main backbone.
- Hydrogen bond: A weak physical attraction, not a strong covalent reaction releasing water.
#14 of 120
SZABMU 2024
Permalink
Which of the following does not have a quaternary structure?
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Quaternary structure only exists if a functional protein requires
multiple, separate polypeptide chains aggregating together.
Solution:- Myoglobin is the oxygen-storing protein found exclusively in muscle tissue.
- Structurally, it consists of just a single, highly folded polypeptide chain (containing one heme group).
- Because it is only a single chain, it functionally maxes out at the Tertiary level of structure. It physically does not have a Quaternary structure.
Why other options are incorrect (they DO have Quaternary structure):- Hemoglobin: Classic tetramer consisting of exactly 4 separate chains (2 alpha, 2 beta).
- Antibodies: Complex Y-shaped molecules consisting of 4 chains (2 heavy, 2 light).
- DNA Polymerase III: A massive, multi-subunit enzymatic complex (holoenzyme) requiring several different chains to function together.
#15 of 120
NUMS 2024
Permalink
Protein with tertiary structures are helpful in:
A
Carrying messages from glands to target organs
B
Maintaining epithelial lining of skin
C
Maintaining the matrix of connective tissues
D
Helping muscle contraction
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Tertiary structures define complex, soluble globular proteins (hormones, enzymes, antibodies), while secondary structures define tough, insoluble fibrous proteins.
Solution:- Hormones (like insulin or glucagon) are chemical messengers secreted by glands.
- To travel through the aqueous bloodstream and perfectly dock into complex, 3D cellular receptors, they must be highly soluble, specifically folded globular proteins with intricate tertiary structures.
- Therefore, Carrying messages from glands to target organs is a direct function relying on tertiary structural folding.
Why other options are incorrect:- Skin lining (Keratin), Connective matrix (Collagen), Muscle contraction (Actin/Myosin): These are all classic examples of tough, long, insoluble fibrous proteins. Their functions rely strictly on highly repetitive Secondary structures forming long strands, rather than 3D tertiary globes.
#16 of 120
NUMS 2024
Permalink
Rebounding is process of straightening the curly hairs, which bond is targeted by oxidizing agents used during the process?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:The macroscopic shape of human hair is determined by permanent covalent cross-links within the keratin protein structure.
Solution:- Hair is composed of keratin, which contains a high proportion of the sulfur-containing amino acid Cysteine.
- When two distant Cysteine residues align, they form strong covalent bonds called Disulphide bridges (S-S bonds). These rigid bridges pull the hair strand into permanent physical curls or waves.
- Chemical hair straightening (rebounding or perming) utilizes reducing agents to purposefully break these specific Disulphide bridges. The hair is pulled straight, and then oxidizing agents are applied to re-form the bonds in the new, straight configuration.
Why other options are incorrect:- Hydrogen bonds: These are weak and are broken simply by wetting the hair (which is why wet hair hangs straight), but they reform immediately upon drying. They don't require harsh chemical oxidizing agents.
- Peptide bonds: Breaking these would completely dissolve and destroy the entire protein backbone, dissolving the hair entirely rather than just straightening it.
#17 of 120
SZABMU 2024 Reconduct
Permalink
Number of amino acids in each alpha chain of hemoglobin is:
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:The primary sequence of human Hemoglobin A is highly conserved and numerically precise.
Solution:- Human hemoglobin consists of four total chains.
- The two shorter alpha (\(\alpha\)) chains each consist of exactly 141 amino acids.
- (The two slightly longer beta (\(\beta\)) chains each consist of exactly 146 amino acids).
Why other options are incorrect:- 146: This is the specific count for the Beta chains, not the Alpha chains.
- 414 / 416: These are random, incorrect numbers holding no biological significance to this structure.
#18 of 120
SZABMU 2024 Reconduct
Permalink
Two amino acids form a dipeptide through:
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Biological monomers are forced together via specific water-removing synthetic reactions.
Solution:- To link two separate amino acids into a unified dipeptide, the carboxyl group of the first must covalently bond to the amino group of the second.
- To free up the bonding electrons required, an \(-OH\) and an \(-H\) are forcefully stripped away from the monomers and expelled as a newly formed water molecule.
- Because a larger molecule is built via the removal of water, this is universally termed a Condensation reaction (or dehydration synthesis).
Why other options are incorrect:- Hydrolysis: The exact opposite; adds water to smash the dipeptide back into two separate amino acids.
- Hydrogen bonding / Ionic bond: These are weak physical interactions that govern 3D folding later on; they do not form the tough covalent backbone required to link monomers.
#19 of 120
SZABMU 2024 Reconduct
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The protein present in blood plasma and involved in blood clotting is:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:The body must maintain the ability to rapidly seal circulatory leaks using a highly specialized, soluble protein precursor.
Solution:- Fibrinogen is a massive, soluble protein continuously synthesized by the liver and floated passively in the blood plasma.
- When a blood vessel is ruptured, an enzymatic cascade is triggered. The enzyme thrombin chops a piece off the soluble Fibrinogen, converting it instantly into insoluble Fibrin.
- These fibrin threads violently polymerize, forming a sticky, fibrous net that traps platelets and red blood cells, effectively creating the solid blood clot.
Why other options are incorrect:- Antibodies: Proteins used to hunt and destroy foreign pathogens (immunity), not for structural clotting.
- Hormones: Chemical messengers.
- Enzymes: Biological catalysts. While enzymes (like thrombin) trigger the process, Fibrinogen is the actual structural protein that forms the clot itself.
#20 of 120
UHS 2024
Permalink
The hydrophilic end of phospholipid molecule is polar because of the presence of:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Amphipathic molecules possess severely contrasting regions of electrical charge.
Solution:- A phospholipid consists of a non-polar glycerol backbone attached to two incredibly non-polar fatty acid tails.
- However, the third binding site on the glycerol is occupied by a massive Phosphate group (\(PO_4^{3-}\)).
- This phosphate group carries a strong, permanent negative electrical charge. Because water is highly polar, it intensely targets and forms hydrogen bonds with this charged region, making the entire 'head' of the molecule highly polar and hydrophilic (water-loving).
Why other options are incorrect:- Fatty Acid: These are the intensely non-polar, hydrophobic "tails" that aggressively repel water.
- Glycerol: Its polar \(-OH\) groups are destroyed during ester bond formation, rendering the central backbone relatively neutral.
- Amine group: While some specific head groups (like choline) have nitrogen, the fundamental universal cause of polarity in all phospholipids is the negatively charged phosphate base.
#21 of 120
SZABMU 2024
Permalink
Which of the following is a basic component of lipid bilayer of plasma membrane?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Membranes require amphipathic molecules (having both polar and non-polar regions) to spontaneously form a bilayer in water.
Solution:- The fundamental building blocks of the membrane bilayer are phospholipids.
- Lecithin (scientifically known as Phosphatidylcholine) is the most abundant, classically textbook example of a major phospholipid found continuously throughout the plasma membranes of both plants and animals.
- Its amphipathic nature (polar choline/phosphate head, non-polar tails) makes it perfectly suited for bilayer formation.
Why other options are incorrect:- Acylglycerol / Triglyceride / Waxes: These are entirely non-polar, hydrophobic molecules used strictly for dense energy storage or waterproofing. Because they completely lack a polar head, they violently clump into spherical droplets in water rather than forming flat, structured bilayers.
#22 of 120
SZABMU 2024 Reconduct
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Which fatty acid would have the highest melting point?
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Melting point in lipids is strictly determined by two factors: saturation (lack of double bonds) and chain length (number of carbons).
Solution:- First, rule out unsaturated fats. Oleic acid has a double bond (kink), preventing tight packing, making it a liquid (oil) with a very low melting point.
- The remaining three are fully saturated (straight chains that pack tightly into solids). For saturated fats, the longer the carbon chain, the more London dispersion forces hold them together, pushing the melting point higher.
- Lauric acid: 12 carbons.
- Palmitic acid: 16 carbons.
- Stearic acid: 18 carbons.
- Because Stearic acid has the longest, fully saturated, unkinked hydrocarbon chain, it possesses the strongest intermolecular forces and thus the highest melting point (it forms very hard, solid fats).
Why other options are incorrect:- Oleic acid is liquid. Lauric and Palmitic are shorter, so they melt at lower temperatures than Stearic.
#23 of 120
SZABMU 2024 Reconduct
Permalink
Lipids that protect plants from water loss are:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Terrestrial plants face the constant threat of desiccation (drying out) from the sun, requiring extreme external waterproofing.
Solution:- Plants secrete a highly hydrophobic, solid, protective lipid layer over their exposed epidermis (leaves, stems, fruits).
- This specific layer is composed entirely of Waxes (specifically forming the cuticle, utilizing a wax polymer called cutin).
- Because waxes are formed from extreme long-chain fatty acids and long-chain alcohols, they are completely insoluble in water and form a rigid, impermeable barrier that traps vital moisture inside the plant.
Why other options are incorrect:- Phospholipids: Used strictly for internal cell membranes, not massive external waterproofing.
- Triglycerides: Used internally for energy storage (e.g., in seeds like peanuts), not on the surface.
- Terpenoids: Used for internal pigments and fragrant volatile oils, not bulk structural waterproofing.
#24 of 120
SZABMU 2024 Reconduct
Permalink
Which of the following is found in both messenger RNA and DNA of a mammalian cell?
A
Double helical structure
D
Sugar phosphate backbone
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:DNA and RNA serve vastly different cellular functions, but they share the exact same fundamental polymer architecture.
Solution:- Both DNA and RNA are classified broadly as nucleic acids.
- As such, they are both built by polymerizing nucleotides. Every single nucleotide, regardless of whether it's destined for DNA or RNA, connects to the next via a phosphodiester bond.
- This creates a continuous, universal Sugar-phosphate backbone that forms the structural exterior of the molecule, serving as the universal scaffolding for both mRNA and DNA alike.
Why other options are incorrect:- Double helical structure: Found almost exclusively in DNA. Mammalian mRNA is inherently single-stranded.
- Thymine: A base found exclusively in DNA (RNA replaces it with Uracil).
- Ribose sugar: Found exclusively in RNA (DNA uses deoxyribose).
#25 of 120
SZABMU 2024 Reconduct
Permalink
Transcription is the process in which an RNA copy of the DNA sequence and coding the gene is produced with the help of an enzyme called:
B
RNA dependent DNA polymerase
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Enzymes in the central dogma are named directly for the polymer they synthesize (build).
Solution:- Transcription is the biological process of reading a DNA blueprint to build a complementary messenger RNA (mRNA) strand.
- The massive enzyme responsible for prying the DNA apart, reading the template, and stitching together the new RNA nucleotides is RNA polymerase (specifically, it polymerizes RNA).
Why other options are incorrect:- DNA polymerase: Synthesizes new DNA during cellular replication, not transcription.
- RNA dependent DNA polymerase: Also known as Reverse Transcriptase; used by retroviruses (like HIV) to turn RNA back into DNA.
- RNA transcriptase: A mostly fabricated/colloquial term not used in formal biochemistry (the actual enzyme is RNA polymerase).
#26 of 120
NUMS 2024
Permalink
Nucleoproteins are involved in:
A
Cell to cell recognition
B
Passing hereditary information to next generation
C
Ensuring fast speed of nerve impulse
D
Acting as a surface marker
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Conjugated molecules are named by combining the names of their constituent parts, dictating their physiological location and function.
Solution:- A Nucleoprotein is a complex formed by the direct binding of a nucleic acid (DNA or RNA) to a protein structure.
- The most prominent biological example is Chromatin/Chromosomes, where long strands of DNA are tightly spooled around basic Histone proteins to protect the delicate genetic code.
- Because these DNA-protein complexes physically constitute the chromosomes, their primary, foundational biological role is passing hereditary information to the next generation safely during cell division.
Why other options are incorrect:- Cell to cell recognition / Surface marker: This is the job of Glycoproteins (sugar + protein) sticking out of the cell membrane, entirely unrelated to nuclear DNA complexes.
- Fast speed of nerve impulse: This relies on the myelin sheath, which is formed by massive amounts of Sphingolipids (lipids), not nucleoproteins.
#27 of 120
SZABMU 2023
Permalink
Second most abundant bio element in human body is:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Understanding the mass percentage composition of the six major biological elements (CHNOPS) is foundational.
Solution:- The total mass of the human body is dominated primarily by just a few key elements:
- 1. Oxygen: ~65% (Most abundant, primarily due to massive water content).
- 2. Carbon: ~18% (The second most abundant, serving as the central backbone for all organic macromolecules).
- 3. Hydrogen: ~10%.
- 4. Nitrogen: ~3%.
Why other options are incorrect:- Oxygen is #1. Hydrogen is #3. Nitrogen is #4. The question specifically asks for the second most abundant.
#28 of 120
ETEA 2023 Retake
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Which of the following is opposite of condensation reaction?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Biological polymers are built and destroyed through opposing water-mediated chemical reactions.
Solution:- Condensation (dehydration synthesis) joins two smaller monomers together into a larger polymer while removing and expelling a water molecule.
- The exact chemical opposite is Hydrolysis, which forcefully introduces a water molecule to cleave the covalent bond holding the polymer together, splitting it back into two smaller monomers.
Why other options are incorrect:- Dehydration: This is merely a synonym for condensation, not the opposite.
- Hydration: Simply dissolving or surrounding a molecule with water (physical change), not cleaving a covalent bond.
- Decarboxylation: Removing a carbon dioxide group, entirely unrelated to polymer backbone synthesis.
#29 of 120
NUMS 2023
Permalink
Thermal stability of organisms in the environment is because of which characteristics of water?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Because living organisms are roughly 70% water, their internal temperature is deeply linked to the thermal properties of water itself.
Solution:- Water molecules are bound together by an extensive network of hydrogen bonds.
- When thermal energy (heat) is applied, much of that energy is absorbed and used strictly to stretch and break these hydrogen bonds, rather than increasing the kinetic speed (temperature) of the molecules.
- This gives water a remarkably high specific heat capacity, meaning organisms can endure massive fluctuations in environmental heat without experiencing dangerous spikes in their own internal body temperature.
Why other options are incorrect:- Solvent property & Ionization: Govern cellular chemical reactions and pH, not thermal resistance.
- Protection: A vague term (water does provide mechanical cushioning like CSF, but thermal stability is strictly a thermodynamic "heat capacity" function).
#30 of 120
UHS 2023
Permalink
Biologically, ____ plays key roles in maintaining the integrity of lipid bilayer membranes.
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Cell membranes are not held together by covalent bonds, but rather by the powerful physical forces exerted by surrounding water.
Solution:- Water molecules are highly polar and constantly seek to form low-energy hydrogen bonds with each other.
- When non-polar (hydrophobic) fatty acid tails are placed in water, they disrupt these hydrogen bonds. Consequently, the water molecules aggressively "squeeze" the tails away to restore their own bonding network.
- This phenomenon, Hydrophobic exclusion, forces the lipid tails into a tight, shielded bilayer core, completely defining and stabilizing the structural integrity of every cell membrane.
Why other options are incorrect:- Hydrophilic exclusion: A non-existent/incorrect term. Polar heads are hydrophilic and actively interact with water, they are not excluded.
- Heat properties: Relate strictly to temperature control, not membrane aggregation.
#31 of 120
ETEA 2023 Retake
Permalink
All are the properties of water excluding:
C
Becomes dense when it freezes
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Water has one profound, life-saving physical anomaly regarding its solid state.
Solution:- Nearly all substances in the universe become denser as they transition from a liquid to a solid because molecular kinetic energy drops, allowing molecules to pack tighter.
- Water is the stark exception. As it approaches freezing (below 4°C), its hydrogen bonds lock into a rigid, open-spaced hexagonal crystal lattice.
- This vast empty space in the lattice means ice is strictly less dense than liquid water, allowing it to float.
- Therefore, the claim that it "becomes dense when it freezes" is physically false.
Why other options are incorrect (they are true properties of water):- Universal solvent & Polar nature: Driven by its dipole moment.
- Hydrogen bonding: The core force defining its behavior.
#32 of 120
ETEA 2023 Retake
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____ is the heat required to convert a gram of water into vapors at its boiling point.
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Thermodynamic definitions relating to phase transitions.
Solution:- The amount of thermal energy specifically required to completely break the intermolecular hydrogen bonds of 1 gram of a liquid, transitioning it entirely into a gas at a constant temperature (boiling point), is defined strictly as its Heat of vaporization.
- For water, this value is exceptionally high (574 kcal/kg), powering the massive cooling effect of sweating.
Why other options are incorrect:- Specific heat capacity: This is the heat required to merely raise the temperature of 1 gram of a substance by 1°C, without changing its phase.
- Heat of ionization / Polarity: Unrelated to thermal phase change measurements.
#33 of 120
NUMS 2023
Permalink
These carbohydrates are sweetest among all carbohydrates:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:The sensation of sweetness is mediated by taste-bud receptors which bind specifically to small, highly soluble molecules.
Solution:- As the chain length of a carbohydrate polymer increases, its solubility and its physical ability to fit into tongue receptors rapidly decrease.
- Monosaccharides (like fructose and glucose) are the smallest, simplest, and most soluble sugar units available, rendering them the absolute sweetest of all carbohydrate classes.
Why other options are incorrect:- Disaccharides (sucrose): Sweet, but generally less so than fructose (a monosaccharide).
- Oligosaccharides & Polysaccharides: As they grow massive (like starch or cellulose), they become completely tasteless and insoluble in the mouth.
#34 of 120
UHS 2023
Permalink
Most of the monosaccharides form a ring structure when in solution. For example ribose will form a five cornered ring known as ____.
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:In an aqueous solution, pentoses and hexoses undergo intramolecular reactions to form stable, closed rings.
Solution:- Ribose is a 5-carbon pentose sugar.
- When it forms a closed ring in solution, it strictly forms a 5-membered ring (four carbon atoms and one oxygen atom in the ring).
- Chemically, any 5-membered sugar ring is termed a "furanose" (named after the chemical furan). Thus, cyclic ribose is technically termed Ribofuranose.
Why other options are incorrect:- Glucopyranose: A 6-membered ring (pyranose) formed by Glucose, not Ribose.
- Glyceraldehyde / Acetaldehyde: Small linear molecules that do not form these complex rings.
#35 of 120
ETEA 2023
Permalink
Lactose is composed of:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Memorizing the constituent monosaccharides of the three primary dietary disaccharides is essential.
Solution:- Lactose is the primary sugar naturally found in mammalian milk.
- It is a disaccharide synthesized by a condensation reaction linking one molecule of Glucose to one molecule of Galactose via a β-1,4-glycosidic bond.
Why other options are incorrect:- Glucose + Fructose: Forms Sucrose (table sugar).
- Glucose + Glucose: Forms Maltose (malt sugar).
#36 of 120
ETEA 2023 Retake
Permalink
Glucose is classified as a ____.
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Carbohydrate classification is strictly based on whether the molecule can be broken down into simpler sugars via hydrolysis.
Solution:- Glucose (\(C_6H_{12}O_6\)) is a single, fundamental, un-bonded sugar unit.
- It cannot be hydrolyzed (broken down by water) into any smaller or simpler sugar molecule.
- Therefore, it is the classic archetype of a Monosaccharide.
Why other options are incorrect:- All other options (Di-, Oligo-, Poly-) are polymers that yield multiple glucose/sugar molecules upon hydrolysis.
#37 of 120
ETEA 2023 Retake
Permalink
Sucrose is hydrolyzed into:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Hydrolysis of a disaccharide yields its exact original building blocks.
Solution:- Sucrose (common cane sugar / table sugar) is formed in plants by linking α-glucose and β-fructose.
- When the enzyme sucrase catalyzes the hydrolysis of sucrose, it splits the α-1,2-glycosidic bond, releasing exactly one molecule of Glucose and one molecule of Fructose into the bloodstream.
Why other options are incorrect:- Glucose + Galactose: This is the hydrolysis product of Lactose, not Sucrose.
- Lactose: Is a disaccharide itself; it is never produced by breaking down another disaccharide.
#38 of 120
SZABMU 2023
Permalink
Which of the following process is involved in decomposition of protein into amino acids?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Biological digestion is entirely reliant on the chemical cleavage of macromolecules using water.
Solution:- When we consume a protein, our digestive enzymes (like pepsin and trypsin) must break the tough, covalent peptide bonds linking the amino acid chain.
- This is accomplished strictly through a Hydrolysis reaction, wherein a single water molecule is forced into the peptide bond, splitting it apart to release individual, absorbable amino acids.
Why other options are incorrect:- Condensation: The exact opposite process; removes water to build the protein up.
- Glycolysis: The metabolic breakdown of glucose for energy, entirely unrelated to protein digestion.
- Fixation: Converting inorganic gas (like \(CO_2\) or \(N_2\)) into organic forms (photosynthesis).
#39 of 120
NUMS 2023
Permalink
Which of the following protein establishes the matrix of bone & cartilage?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:The structural integrity of skeletal connective tissue relies on a highly specialized extracellular fibrous protein network.
Solution:- Collagen is the primary structural protein of the extracellular matrix in all connective tissues.
- It forms tough, inextensible fibers that act as the physical scaffold (matrix) into which calcium phosphate is deposited to form rigid bone, or proteoglycans are deposited to form flexible cartilage.
Why other options are incorrect:- Keratin: Structural protein, but strictly for external appendages like hair, nails, and epidermis, not internal skeletal matrices.
- Elastin: Provides elasticity to lungs and arteries, not rigid skeletal structure.
- Histone: A nuclear globular protein used to spool DNA.
#40 of 120
NUMS 2023
Permalink
Most abundant organic compound in mammalian cells are:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:It is crucial to distinguish between total compounds and
organic compounds in cellular composition.
Solution:- While Water is universally the most abundant compound overall (70%), it is strictly an inorganic molecule.
- The question explicitly asks for the most abundant organic compound (carbon-based macromolecules).
- Proteins make up roughly 18% of the total cellular mass (over half of the dry weight of a cell), making them the most abundant organic compounds in any mammalian cell by a massive margin.
Why other options are incorrect:- Water: Inorganic.
- Lipids (~3%) & Carbohydrates (~4%): These represent significantly smaller mass fractions compared to the ubiquitous presence of structural and enzymatic proteins.
#41 of 120
SZABMU 2023
Permalink
Select the protein providing support for the connective tissues:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Connective tissues (tendons, ligaments, fascia) require extreme tensile strength to prevent tearing under tension.
Solution:- Collagen forms unique triple-helices that assemble into massive, highly cross-linked fibrils.
- This specific fibrous architecture provides incredible tensile strength, making it the primary, unyielding support protein for the entire mammalian connective tissue system.
Why other options are incorrect:- Elastin: Found in connective tissue, but provides stretch/recoil rather than unyielding rigid support.
- Keratin: Found strictly in epithelial structures (skin/hair), not internal connective tissue.
- Histones: Nuclear proteins that organize DNA.
#42 of 120
SZABMU 2023
Permalink
Fibrous proteins do not take part in:
C
Oxygen transport in blood
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Fibrous proteins perform static, mechanical, and structural roles, whereas globular proteins perform dynamic, functional, transport, and catalytic roles.
Solution:- Oxygen transport in blood is solely carried out by hemoglobin.
- Hemoglobin is a highly complex, 3D folded, functional globular protein, entirely lacking the tough, extended string-like structure of a fibrous protein.
- Therefore, fibrous proteins have absolutely no role in gas transport.
Why other options are incorrect:- Formation of nails: Keratin (fibrous).
- Blood clotting: Fibrin (fibrous polymer formed from fibrinogen).
- Muscle contraction: Actin and myosin (fibrous structures generating mechanical tension).
#43 of 120
ETEA 2023
Permalink
In sickle cell hemoglobin molecule, glutamic acid, is replaced by:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:A single point mutation in DNA can radically alter the primary, and thus tertiary/quaternary, structure of a protein.
Solution:- Sickle cell anemia is caused by a precise point mutation in the gene encoding the beta-chain of hemoglobin.
- This genetic error causes a highly polar, hydrophilic amino acid (Glutamic acid) at position 6 to be erroneously replaced by a highly non-polar, hydrophobic amino acid (Valine).
- Because valine is hydrophobic, it tries to hide from water by sticking to other hemoglobin molecules, causing the proteins to polymerize into long, sharp fibers that distort the red blood cell into a sickle shape.
Why other options are incorrect:- This is a specific memorization fact. Proline, Glutamine, and Glycine are not the specific amino acid substituted in this famous genetic disorder.
#44 of 120
ETEA 2023
Permalink
____ is found in the exoskeleton of crabs.
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Different phylogenetic kingdoms employ distinct structural polysaccharides to build their protective outer boundaries.
Solution:- Arthropods (such as crabs, lobsters, and insects) possess a hard outer exoskeleton.
- This exoskeleton is built entirely from Chitin, a tough, nitrogenous structural polysaccharide made of highly cross-linked chains of N-acetylglucosamine.
Why other options are incorrect:- Cellulose & Hemi-cellulose: Exclusive structural components of the plant kingdom's cell walls.
- Murein (Peptidoglycan): The defining structural component of bacterial cell walls.
#45 of 120
ETEA 2023
Permalink
Amino acids mainly differ from each other by the difference in their:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:All amino acids share a universal backbone, yet 20 vastly different types exist to build complex proteins.
Solution:- Every single amino acid possesses the exact same structural backbone: a central alpha carbon bonded to an amino group, a carboxyl group, and a solitary hydrogen atom.
- The only structural component that varies from one amino acid to the next is the fourth bond: the highly variable side chain, universally termed the R-group.
- It is this specific R-group that dictates whether an amino acid is acidic, basic, polar, or non-polar.
Why other options are incorrect:- Amino, Carboxyl, and Hydrogen: These three groups are absolutely identical across all 20 standard amino acids; they do not differ.
#46 of 120
SZABMU 2023
Permalink
Three hydrophobic fatty acid tails and a glycerol molecule join to form a:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Biological nomenclature directly reflects the stoichiometry of the molecule's constituents.
Solution:- The prefix "Tri-" means three.
- When a single glycerol molecule undergoes dehydration synthesis to bond covalently via ester linkages to exactly three fatty acid tails, it forms a massive, fully non-polar lipid used for energy storage.
- By direct definition, this molecule is a Triglyceride (Triacylglycerol).
Why other options are incorrect:- Mono/Diglyceride: Contain 1 and 2 fatty acids, respectively.
- Phospholipid: Contains exactly 2 fatty acids. The third spot on the glycerol is occupied by a polar phosphate group instead of a third tail.
#47 of 120
ETEA 2023
Permalink
Choose the unsaturated fatty acid among the following:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Fatty acids are classed as saturated (no double bonds) or unsaturated (contains double bonds).
Solution:- Oleic acid (18 carbons) contains exactly one carbon-carbon double bond (it is monounsaturated), making it the primary liquid fat found in olive oil.
Why other options are incorrect:- Palmitic (16C), Stearic (18C), and Arachidic (20C) acids: These are all classic examples of fully saturated fatty acids, forming straight chains that are solid at room temperature.
#48 of 120
NUMS 2023
Permalink
C-H bonds in lipids are important:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:The massive thermodynamic yield of lipids is rooted strictly in their chemical structure.
Solution:- During cellular respiration, high-energy electrons are harvested directly from non-polar C-H bonds to power the electron transport chain.
- Lipids contain incredibly long aliphatic tails composed almost entirely of C-H bonds.
- Because they possess such a massive proportion of these easily oxidizable bonds compared to carbohydrates, the specific fundamental importance of C-H bonds is providing more energy (more than double the yield per gram).
Why other options are incorrect:- Insulation / Cuticle: These are macroscopic physical functions of the lipid molecule as a whole (due to its hydrophobicity), not the specific thermodynamic importance of the individual C-H bond itself.
- Exoskeleton: Formed by chitin (a carbohydrate), not lipids.
#49 of 120
SZABMU 2023
Permalink
The sugar which is part of ribonucleic acid is:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Nucleic acids are named directly after the pentose sugar making up their backbone.
Solution:- Ribonucleic acid (RNA) utilizes the standard 5-carbon sugar Ribose (\(C_5H_{10}O_5\)) in every single one of its nucleotide building blocks.
Why other options are incorrect:- Deoxyribose: The sugar found exclusively in DNA (missing one oxygen atom).
- Ribulose / Deoxyribulose: These are ketose sugars; nucleic acid backbones strictly require the specific ring structure formed by aldoses.
#50 of 120
SZABMU 2023
Permalink
The basic structural framework of all types of membranes is:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Biological membranes are fundamentally fluid mosaics composed of two distinct macromolecule classes working in tandem.
Solution:- The universal architecture of all biological membranes is a phospholipid bilayer extensively embedded with integral and peripheral proteins.
- Because a membrane is essentially a massive, co-assembled structure of lipids providing the barrier and proteins providing the function, this entire structural framework is broadly classified as a massive Lipoprotein complex (a conjugated structure of lipids and proteins).
Why other options are incorrect:- Glycolipids & Glycoproteins: These are minor surface modifications for recognition, not the bulk basic structural framework spanning the entire membrane.
- Nucleoproteins: Complexes of DNA/RNA and protein (like chromatin or ribosomes), completely unrelated to membranes.
#51 of 120
ETEA 2023
Permalink
The conjugated molecule that is primarily present in egg albumin is:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Ovalbumin (the main protein in egg white) requires slight carbohydrate modification to maintain solubility and structure.
Solution:- Egg albumin (ovalbumin) is a massive globular storage protein.
- However, it is not a pure protein; it has short carbohydrate chains covalently attached to its surface to enhance its solubility in the aqueous environment of the egg white.
- Because it is a protein chemically bonded to a carbohydrate, it is classified specifically as a Glycoprotein.
Why other options are incorrect:- Lipoprotein: Found in blood plasma (HDL/LDL) for lipid transport, not bulk egg white storage.
- Nucleoprotein: Found in the nucleus (chromatin).
- Glycolipid: Found on cell membranes, entirely lacking the massive protein component of albumin.
#52 of 120
UHS 2022
Permalink
Hydrolysis process is a reverse of ____ process.
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Hydrolysis is fundamentally the reverse of condensation (also known as dehydration synthesis).
Solution:- In a condensation reaction, two monomers join together. A hydroxyl group (-OH) is removed from one monomer and a hydrogen atom (-H) from the other, synthesizing water and forming a covalent bond.
- In hydrolysis, the polymer is broken down into its constituent monomers by the addition of a water molecule, which splits back into a hydroxyl group and a hydrogen atom.
Why other options are incorrect:- Photolysis: The breakdown of molecules caused by light.
- Deduction/Convection: Unrelated logical and physical processes.
#53 of 120
NUMS 2022
Permalink
Hydrolysis is the breakdown of polymers into its monomers by the addition of:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Hydrolysis literally translates to 'water-splitting' (hydro = water, lysis = to break).
Solution:- During hydrolysis, polymers are broken down into monomers strictly by the addition of water.
- The water molecule splits: a hydroxyl group is attached to one monomer, and a hydrogen atom is attached to the other monomer to satisfy their valencies.
- Digestion reactions in the human body are classic examples of enzyme-controlled hydrolysis.
Why other options are incorrect:- Hydrogen / Hydroxyl group: These are individual components of water, but the entire water molecule must be added to facilitate the reaction.
- Nitrogen: Unrelated to the cleavage of standard glycosidic, peptide, or ester bonds.
#54 of 120
ETEA 2022
Permalink
The most abundant element present in human body is ____.
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Bio-elements combine to form the living mass of an organism. While Oxygen is the most abundant element overall (65%), it is not listed in the options.
Solution:- We must select the most abundant element from the given choices based on standard human body composition percentages:
- Carbon: 18%
- Nitrogen: 3%
- Sulphur: 0.25%
- Manganese: Trace element
- Therefore, Carbon is the most abundant element among the provided options.
Why other options are incorrect:- Nitrogen, Sulphur, and Manganese make up significantly smaller percentages of human body mass compared to Carbon.
#55 of 120
NUMS 2022
Permalink
Due to its high heat of vaporization, water plays important role in living organisms as:
A
Thermal shock resistant
B
Being and excellent solvent
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Heat of vaporization is the energy required to convert a liquid to a gas.
Solution:- Because water requires a massive influx of heat energy to break its hydrogen bonds and vaporize, evaporation removes substantial heat from the surface it leaves behind.
- This gives animals an efficient way to release excess body heat in hot environments (e.g., sweating or panting), strictly acting as a cooling agent.
Why other options are incorrect:- Thermal shock resistant: This is related to water's High Specific Heat Capacity, which prevents rapid temperature fluctuations, not vaporization.
- Solvent / Membrane stabilizer: Governed by polarity and hydrophobic exclusion, not phase changes.
#56 of 120
NUMS 2022
Permalink
Which of the following molecules would yield glucose and fructose on hydrolysis?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Disaccharides yield two monosaccharide monomers upon hydrolysis (the breaking of the glycosidic bond).
Solution:- Sucrose (table sugar) is a disaccharide composed of an alpha-glucose molecule linked to a beta-fructose molecule.
- When hydrolyzed by the enzyme sucrase (or dilute acid), it strictly yields one molecule of glucose and one molecule of fructose.
Why other options are incorrect:- Maltose: Yields two molecules of glucose.
- Lactose: Yields one glucose and one galactose.
- Starch: A polysaccharide that yields thousands of glucose units, not fructose.
#57 of 120
SZABMU 2022
Permalink
Which property of water enables it to act as temperature stabilizer in living organisms?
A
High heat of vaporization
B
High specific heat capacity
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Temperature stabilization implies resisting sudden fluctuations in internal or environmental temperature.
Solution:- Due to extensive intermolecular hydrogen bonding, water has a high specific heat capacity.
- This means water has a great ability to absorb massive amounts of thermal energy with only a minimal change to its own temperature.
- This property buffers cellular environments against extreme thermal shocks, acting as a crucial thermo-stabilizer.
Why other options are incorrect:- High heat of vaporization: Enables cooling through phase change (sweating), but specific heat capacity is what actively prevents the temperature from spiking in the first place.
- High polarity: Relates to solvent properties, not thermal properties.
#58 of 120
BUMHS 2022
Permalink
Which of the following is antagonistic to condensation?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Antagonistic means acting in direct opposition.
Solution:- Condensation (Dehydration Synthesis): Two monomers are joined together to form a polymer, releasing a molecule of water in the process.
- Hydrolysis: A polymer is broken down into two monomers by the consumption/addition of a water molecule.
- Therefore, hydrolysis is the exact biological and chemical antagonist (reverse) of condensation.
Why other options are incorrect:- Dehydration: This is synonymous with condensation, not antagonistic to it.
- Hydration: Simply means adding water to a substance, but 'hydrolysis' specifically implies breaking a covalent bond using water.
- Decarboxylation: Removal of carbon dioxide, unrelated to water-mediated monomer linking.
#59 of 120
DUHS 2022
Permalink
Water is the most abundant compound in living organisms its amount varies from:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Water is the fundamental matrix of life, making up the vast bulk of cellular and extracellular fluid.
Solution:- In almost all living organisms, water is the most abundant compound.
- Across different species and tissue types, the generalized overall water content typically ranges from 70% to 90% of the total body mass.
- For instance, humans are roughly 70% water, while some organisms like jellyfish reach up to 99%.
Why other options are incorrect:- Values like 10-60% drastically underestimate the required aqueous environment needed for biochemical reactions to sustain life.
#60 of 120
NUMS 2022
Permalink
Which of the following is not a carbohydrate?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Not all molecules that loosely fit the empirical formula of a carbohydrate are biologically classified as carbohydrates.
Solution:- Lactic acid has the formula \( C_3H_6O_3 \), which mathematically fits the \( C_n(H_2O)_n \) ratio.
- However, structurally, it contains a carboxylic acid group (-COOH) and a single hydroxyl group, not the polyhydroxy aldehyde/ketone structure required to be a sugar.
- It is a metabolic by-product of anaerobic respiration, completely distinct from carbohydrates.
Why other options are incorrect:- Glucose & Sucrose: Standard textbook carbohydrates.
- Rhamnose: A naturally occurring deoxy sugar (a true carbohydrate, despite deviating from the strict \(1:2:1\) water ratio).
#61 of 120
SZABMU 2022
Permalink
Which bond is the potential source of chemical energy for cellular activities?
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Cellular respiration extracts thermodynamic energy stored in highly reduced organic molecules.
Solution:- The electrons shared within the non-polar Carbon-Hydrogen (C-H) bonds are held relatively loosely compared to polar bonds (like C=O).
- Because they are held loosely, these electrons possess high potential energy.
- During cellular respiration, these high-energy electrons are stripped from the C-H bonds and allowed to 'fall' towards highly electronegative oxygen, releasing massive amounts of usable chemical energy to synthesize ATP.
Why other options are incorrect:- C=O: Highly oxidized bonds holding electrons tightly in a low-energy state.
- C-N / C-R: Not the primary thermodynamic fuel utilized during massive oxidative phosphorylation.
#62 of 120
SZABMU 2022
Permalink
Which of the following carbohydrates are the sweetest among all?
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Sweetness is inversely proportional to the complexity and size of the carbohydrate polymer.
Solution:- Monosaccharides (like fructose and glucose) are structurally the smallest and simplest sugars.
- Their small size and exposed functional groups easily interact with the sweet-taste receptors on the tongue, making them biologically the sweetest class of carbohydrates. (Fructose, a monosaccharide, is notoriously the sweetest naturally occurring sugar).
Why other options are incorrect:- As sugar chains grow longer (Disaccharides → Oligosaccharides → Polysaccharides), they lose their ability to interact with taste receptors. Polysaccharides like starch and cellulose are entirely tasteless.
#63 of 120
ETEA 2022
Permalink
Ribose is a pentose sugar (5-carbon) that contains:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Monosaccharides are classified structurally as either aldoses (having an aldehyde group at Carbon-1) or ketoses (having a ketone group at Carbon-2).
Solution:- Ribose is an aldo-pentose. It possesses a terminal aldehyde group (-CHO) at carbon-1.
- Its structural isomer, Ribulose, is the ketose version possessing a ketone group.
Why other options are incorrect:- Ketone group: Found in Ribulose and Fructose.
- Carboxyl / Ester groups: These characterize organic acids and lipids, not standard sugar molecules.
#64 of 120
BUMHS 2022
Permalink
Diastase/amylase acts on:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Enzymes are highly substrate-specific.
Solution:- Amylase (also historically called diastase) is specifically designed to recognize and cleave the α-1,4-glycosidic linkages found exclusively in starch (and glycogen).
- It breaks the large starch polymer down into smaller fragments and ultimately into the disaccharide maltose.
Why other options are incorrect:- Lactose, Sucrose, Maltose: These are disaccharides digested by entirely different, specific enzymes (lactase, sucrase, and maltase, respectively).
#65 of 120
BUMHS 2022
Permalink
Maltose is a:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Saccharides are classified by the number of monomeric units joined together.
Solution:- Maltose (malt sugar) is synthesized by the condensation of exactly two glucose molecules linked by an α-1,4-glycosidic bond.
- Because it consists of strictly two units, it is classified as a Disaccharide.
Why other options are incorrect:- Monosaccharide: A single unit (e.g., glucose).
- Oligosaccharide / Polysaccharide: Consist of 3 to 10 units, and hundreds of units, respectively.
#66 of 120
DUHS 2022
Permalink
Synthesis of disaccharide by condensation two glucose joined by glycosidic linkage to form:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Knowing the specific monosaccharide components of common disaccharides is fundamental biochemistry.
Solution:- When a condensation reaction occurs strictly between two α-glucose molecules, the resulting disaccharide product is Maltose.
Why other options are incorrect:- Lactose: Formed by Glucose + Galactose.
- Fructose & Galactose: These are single monosaccharide units, not disaccharide products.
#67 of 120
DUHS 2022
Permalink
Molecules of amylose consists of unbranched chains of hundreds of glucose sub units, join together by:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Starch comes in two forms: unbranched amylose and highly branched amylopectin.
Solution:- Amylose is the simple, unbranched, linear component of starch.
- It forms a helical chain because its glucose units are linked strictly end-to-end via α-1,4-glycosidic linkages (Carbon 1 of one glucose binding to Carbon 4 of the next).
Why other options are incorrect:- Branching in amylopectin/glycogen occurs at 1-6 linkages. The other listed linkages (1-2, 1-3, 2-3) do not form the standard backbone of plant starch.
#68 of 120
UHS 2022
Permalink
Unique three-dimensional shape of the fully folded polypeptide constitutes:
A
Primary structure of protein
B
Quaternary structure of protein
C
Secondary structure of protein
D
Tertiary structure of protein
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Protein folding reaches functional maturity at specific structural hierarchies.
Solution:- The Tertiary structure is defined exactly as the ultimate, overall three-dimensional shape of a single, fully folded polypeptide chain.
- It is uniquely determined by complex interactions (disulfide bridges, hydrophobic exclusions, ionic bonds, hydrogen bonds) strictly between the varying R-groups of the constituent amino acids.
Why other options are incorrect:- Primary/Secondary: Refer only to linear sequence and localized coils/sheets, lacking full 3D completion.
- Quaternary: Refers to the arrangement of multiple distinct polypeptide subunits together (e.g., Hemoglobin), rather than a single folded chain.
#69 of 120
NUMS 2022
Permalink
Which of the following molecules contains amino acid?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Macromolecules are composed of specific fundamental monomers. Proteins are polymers of amino acids.
Solution:- Collagen is the most abundant structural protein in the mammalian body, found extensively in connective tissues.
- Because it is a protein, it is synthesized exclusively from amino acid monomers linked by peptide bonds.
Why other options are incorrect:- Cellulose & Sucrose: These are carbohydrates, composed entirely of monosaccharide sugars (glucose/fructose).
- Ascorbic acid: Also known as Vitamin C, it is a small, water-soluble organic compound (a sugar acid), not a protein.
#70 of 120
SZABMU 2022
Permalink
Select an example of fibrous protein:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Proteins are structurally classed into two main groups: fibrous (long, structural strands) and globular (spherical, functional folded units).
Solution:- Collagen consists of three polypeptide chains wrapped around each other into a tough, rope-like triple helix.
- This extended, uncoiled macroscopic shape makes it the classic example of a fibrous protein, granting immense tensile strength to tendons, ligaments, and skin.
Why other options are incorrect:- Enzymes, Hemoglobin, Hormones: These perform highly specific, dynamic metabolic tasks (catalysis, transport, signaling) and must fold into complex 3D spherical active shapes, making them strictly globular proteins.
#71 of 120
SZABMU 2022
Permalink
Which function is not performed by proteins?
A
Providing structural support to cell
B
Catalyzing biochemical reactions
C
Transporting materials across cell membrane
D
Providing insulation against heat loss
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:While proteins are the most versatile macromolecules in the body, certain passive, long-term physiological roles are delegated to other biomolecules.
Solution:- Providing insulation against heat loss is fundamentally the physiological role of adipose tissue (fat), which consists of lipids (specifically triglycerides).
- Lipids form thick, non-conductive subcutaneous layers (like blubber) that trap heat, a function proteins do not inherently perform.
Why other options are incorrect:- Structural support: Performed by fibrous proteins like cytoskeleton, collagen, and keratin.
- Catalyzing reactions: Performed by enzymatic proteins.
- Transporting materials: Performed by channel/carrier proteins and hemoglobin.
#72 of 120
ETEA 2022
Permalink
Proteins are macromolecules formed of units known as amino acids. The amino acids in which the variable group (R) is represented by an H atom is:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:The chemical identity and properties of each amino acid are dictated solely by its unique 'R' side-chain.
Solution:- Glycine is the simplest, most basic amino acid found in nature.
- Its variable R-group consists of just a single Hydrogen (H) atom.
- Because of this tiny side chain, glycine can comfortably fit into incredibly tight structural turns within protein folding architectures, such as the collagen triple helix.
Why other options are incorrect:- Alanine: R-group is a methyl group (\(-CH_3\)).
- Phenylalanine: R-group contains a large, bulky benzyl ring.
- Lysine: R-group is a long, positively charged hydrocarbon chain ending in an amino group.
#73 of 120
ETEA 2022
Permalink
Haemoglobin is a:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Hemoglobin is the primary oxygen-transporting molecule in the blood of vertebrates.
Solution:- Haemoglobin is a complex, conjugated globular protein.
- It consists of four distinct polypeptide chains (two alpha and two beta chains), heavily folded into a Quaternary structure around non-protein heme groups that bind oxygen.
Why other options are incorrect:- Enzyme: Although it is a protein, hemoglobin does not catalyze chemical reactions; it passively binds and transports gas, so it is a transport protein, not an enzyme.
- Carbohydrate / Nucleic acid: Completely different macromolecule classes.
#74 of 120
ETEA 2022
Permalink
The most common protein in nature is ____.
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Biological abundance is determined by evaluating the total biomass of organisms on Earth, which is overwhelmingly dominated by photosynthetic life.
Solution:- Rubisco (Ribulose-1,5-bisphosphate carboxylase-oxygenase) is the primary enzyme responsible for carbon fixation in the Calvin cycle of photosynthesis.
- Because it is present in massive quantities in the chloroplasts of almost every single plant and photosynthetic algae across the globe, it is unequivocally recognized as the most abundant protein in the world.
Why other options are incorrect:- Collagen: The most abundant protein in the animal kingdom (roughly 25-35% of mammalian protein mass), but animals represent a tiny fraction of global biomass compared to plants.
- Keratin & DNAase: Abundant in specific tissues, but dwarfed globally by Rubisco.
#75 of 120
ETEA 2022
Permalink
A haemoglobin molecule consists of ____ amino acids.
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Hemoglobin structure is a classic textbook example of quaternary protein assembly.
Solution:- A standard human Hemoglobin A molecule is a tetramer, consisting of exactly four polypeptide chains:
- Two alpha (\(\alpha\)) chains, each containing exactly 141 amino acids (Total = 282).
- Two beta (\(\beta\)) chains, each containing exactly 146 amino acids (Total = 292).
- Summing them up: \( 282 + 292 = \) 574 total amino acids.
Why other options are incorrect:- The numbers 474, 674, and 874 do not correlate with the highly conserved genetic sequence encoding mammalian hemoglobin chains.
#76 of 120
BUMHS 2022
Permalink
Two simplest amino acids are:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:The complexity of an amino acid is dictated by the size and branching of its R-group.
Solution:- Glycine: The absolute simplest amino acid, with an R-group consisting of just a hydrogen atom (\(-H\)).
- Alanine: The second simplest amino acid, with an R-group consisting of just a small methyl group (\(-CH_3\)).
- These two have the smallest molecular weights and least complex side chains.
Why other options are incorrect:- Trypsin: This is not an amino acid at all; it is a massive, complex digestive protein (enzyme).
- Glutamate: Contains a larger, negatively charged carboxylic acid side chain, making it significantly more complex.
#77 of 120
BUMHS 2022
Permalink
Which protein establishes the matrix of bone and cartilage?
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Connective tissues rely heavily on extracellular fibrous proteins to resist mechanical stress.
Solution:- Collagen is the primary structural protein secreted into the extracellular space.
- It forms an incredibly dense, tough fibrous network (matrix) that acts as the physical scaffolding for cartilage, tendons, ligaments, and the calcified structure of bone.
Why other options are incorrect:- Hemoglobin & Myoglobin: Globular proteins strictly dedicated to oxygen transport/storage.
- Fibrinogen: A soluble plasma protein that converts to fibrin to facilitate blood clotting, not bone structure.
#78 of 120
SZABMU 2022
Permalink
Three hydrophobic fatty acid tails and a glycerol molecule join to form:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Acylglycerols are formed by linking fatty acid chains to the three hydroxyl groups of a glycerol backbone.
Solution:- Glycerol is a 3-carbon alcohol with exactly three reactive hydroxyl (\(-OH\)) sites.
- When all three of these sites undergo condensation reactions to bond with exactly three distinct fatty acid tails, the resulting molecule is a neutral fat scientifically known as a Triglyceride (or Triacylglycerol).
Why other options are incorrect:- Monoglyceride / Diglyceride: Contain only one or two fatty acid tails, respectively.
- Phospholipid: Contains exactly two fatty acid tails, with the third glycerol site occupied by a charged phosphate group.
#79 of 120
ETEA 2022
Permalink
The glycerol is a ____ carbon compound.
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Glycerol acts as the universal foundational backbone for triacylglycerols and phospholipids.
Solution:- Glycerol (also known as glycerin) is structurally a simple polyol (sugar alcohol).
- Its chemical formula is \(C_3H_8O_3\).
- Structurally, it consists of exactly three carbon atoms, each holding one reactive hydroxyl (\(-OH\)) group available to form ester bonds with fatty acids.
Why other options are incorrect:- Compounds with four, five, or six carbons (like ribose or glucose) belong to entirely different carbohydrate classes and are not the lipid backbone.
#80 of 120
DUHS 2022
Permalink
This lipid is most common abundant richest source of energy in plant, and animal body:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Organisms require an extremely dense, lightweight storage molecule for long-term energy reservoirs.
Solution:- Acylglycerols (specifically, Triacylglycerols or neutral fats/oils) are dedicated entirely to massive energy storage.
- Because they are completely non-polar, they can be stored in massive anhydrous droplets within adipose cells (in animals) or seeds (in plants) without dragging heavy water weight along.
- They pack more than double the caloric energy of carbohydrates, making them unequivocally the richest and most abundant energy source.
Why other options are incorrect:- Phospholipids: Highly structural, dedicated to building membranes, not bulk energy storage.
- Carotenoids & Terpenoids: Minor lipid pigments and signaling molecules, existing in tiny quantities.
#81 of 120
UHS 2022
Permalink
Which of the following is a conjugated molecule?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Conjugated molecules are complex structures formed by the covalent bonding of two entirely different classes of biological macromolecules.
Solution:- A Glycoprotein is formed when short chains of carbohydrates (glyco-) are covalently bonded to a polypeptide backbone (protein).
- Because it merges two distinct fundamental macromolecule groups into one functional unit (often used for cell surface recognition), it is officially classified as a conjugated molecule.
Why other options are incorrect:- Protein, Lipid, Vitamins: These are all simple, single-class molecules. They are not conjugated to a secondary, distinct chemical group.
#82 of 120
PMC 2020
Permalink
Which property of water helps to maintain the integrity of lipid membranes?
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:The structural integrity of biological membranes relies on how water interacts with non-polar substances.
Solution:- Water molecules are highly polar and form strong hydrogen bonds with each other.
- When non-polar (hydrophobic) molecules like the fatty acid tails of lipids are in an aqueous environment, water molecules tend to 'exclude' them to maximize their own hydrogen-bonding network.
- This phenomenon, known as hydrophobic exclusion, forces lipid tails to aggregate inward away from water, thereby driving the spontaneous formation and structural stability of the lipid bilayer membrane.
Why other options are incorrect:- While hydrogen bonding drives the exclusion, 'hydrophobic exclusion' is the direct specific property that forces lipids into a bilayer formation.
- Cohesion/Adhesion and Specific heat regulate water transport and thermal stability, respectively, not membrane formation.
#83 of 120
PMC 2020
Permalink
Water acts as universal solvent because of:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:A solvent dissolves solutes. Water is considered a 'universal solvent' because it dissolves more substances than any other liquid.
Solution:- Water's ability to act as a powerful solvent is primarily due to its high polarity.
- The partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms allow water molecules to attract and surround charged ions and other polar molecules, breaking them apart and keeping them in solution.
Why other options are incorrect:- Hydrogen bonding: This is a consequence of water's polarity and aids in dissolving, but the foundational reason it interacts with ionic compounds (like NaCl) is its dipole nature/polarity.
- Cohesion/Adhesion & Heat of vaporization: These govern physical fluid dynamics and thermal regulation, not solvent capacity.
#84 of 120
PMC 2020
Permalink
Monosaccharides have a general formula represented by:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:The term "carbo-hydrate" historically stems from the observation that these molecules appear to be "hydrates of carbon".
Solution:- The general stoichiometric formula for simple monosaccharides is typically represented as \( C_n(H_2O)_n \).
- This reflects that for every carbon atom, there is roughly the equivalent of one water molecule (two hydrogens and one oxygen), yielding a 1:2:1 ratio of C:H:O.
- Here, \( n \) is a whole number ranging from 3 to 7.
Why other options are incorrect:- \( C_5(H_2O)_n \): Incorrectly limits the carbon count strictly to 5.
- \( C(H_2O)_n \): Suggests only one carbon atom exists in the molecule, which is chemically impossible for sugars.
#85 of 120
PMC 2020
Permalink
Lipids store double amount of energy as compared to carbohydrates because of:
A
High proportion of oxygen
B
Low proportion of carbon
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:The thermodynamic potential of a biological fuel depends entirely on its state of reduction (availability of oxidizable hydrogen).
Solution:- The vast majority of a lipid's molecular structure is a long aliphatic chain composed purely of carbons bonded to hydrogens.
- This high proportion of C-H bonds provides an abundance of easily strippable, high-energy electrons that power the electron transport chain to make ATP.
- Carbohydrates, in contrast, have a much lower C-H proportion because many of their carbons are already bonded to oxygen (hydroxyls), meaning they are "partially burned" fuels.
Why other options are incorrect:- High proportion of oxygen / High CO ratio: These represent an oxidized state (lower energy potential), characteristic of carbohydrates, not lipids.
- Low proportion of carbon: Lipids actually have massive carbon chains.
#86 of 120
MDCAT 2019
Permalink
If water has high latent heat of vaporization, how this property of water could be helpful to plants and animals?
A
It will keep their temperature very high
B
With the release of large amount of water vapors, a small amount of heat loss can take place
C
With the release of small amount of water vapors, a great amount of heat loss can take place
D
No cooling effect with the release of even large amount of water vapors
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:The specific heat of vaporization of water is very high due to extensive hydrogen bonding.
Solution:- Water absorbs a massive amount of heat as it changes from a liquid state to a gaseous state.
- Because of this high energy requirement, the evaporation of just a small amount of water effectively carries away a great amount of heat.
- For example, the evaporation of only 2 mL out of 1 liter of water lowers the temperature of the remaining 998 mL by a full 1°C. This provides a highly efficient cooling mechanism for organisms (like sweating in animals or transpiration in plants).
Why other options are incorrect:- Option B: The relationship is inverted; a small volume of vapor releases a large amount of heat, not vice versa.
- Options A & D: Contradict the fundamental physical reality that evaporation produces a profound cooling effect.
#87 of 120
MDCAT 2019
Permalink
Starch is present in tuber, fruits and grains but absent in animal cells. Instead, animals have a substance stored in liver and muscles known as:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Both plants and animals require a macromolecular storage form of glucose to prevent osmotic lysis.
Solution:- Plants store excess glucose as starch.
- Animals store excess glucose as a highly branched polysaccharide known as glycogen.
- Glycogen is often colloquially referred to as 'animal starch' and is stored abundantly in the liver and skeletal muscles.
Why other options are incorrect:- Glucose/Galactose: Simple monomers, not bulk storage molecules.
- Glucagon: A hormone secreted by the pancreas that triggers the breakdown of glycogen; it is a protein, not a carbohydrate.
#88 of 120
MDCAT 2019
Permalink
The covalent bond or bridge between two monosaccharides to form a disaccharide is called a:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Different biological macromolecules rely on specific signature covalent bonds.
Solution:- The specific oxygen bridge formed between two sugar monomers after a condensation reaction is called a glycosidic bond (or glycosidic linkage).
Why other options are incorrect:- Peptide bond: Found in proteins.
- Phosphodiester bond: Found in nucleic acids.
- Ester bond: Found in lipids.
- Hydrogen bond: A weak intermolecular force, not the strong covalent bridge uniting monomers.
#89 of 120
MDCAT 2019
Permalink
Which is an example of a disaccharide?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Carbohydrates are categorized by the number of monomeric units they contain.
Solution:- Lactose (milk sugar) is a disaccharide comprised of precisely two monomers: glucose and galactose linked by a β-1,4-glycosidic bond.
Why other options are incorrect:- Starch & Glycogen: Polysaccharides consisting of hundreds to thousands of glucose monomers.
- Fructose: A simple single-unit monosaccharide.
#90 of 120
ETEA 2019
Permalink
____ is stored in animal cells.
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Energy storage molecules differ structurally between the plant and animal kingdoms.
Solution:- Animals synthesize and store glycogen as their primary short-term energy reserve carbohydrate, sequestering it mainly within hepatocytes (liver cells) and myocytes (muscle cells).
Why other options are incorrect:- Starch: The storage polysaccharide of plants.
- Cellulose: The structural polysaccharide of plant cell walls.
- Sucrose: A transport disaccharide synthesized exclusively in plants.
#91 of 120
AJK 2019
Permalink
Pure form of cellulose is:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Cellulose is a linear β-D-glucose polymer found heavily in nature.
Solution:- Cotton fibers are renowned for being almost entirely composed of cellulose (upwards of 90-95%), representing the purest natural form of cellulose available.
Why other options are incorrect:- Paper & Cellophane: These are manufactured, derivative products made from cellulose, subjected to chemical processing and contain impurities/additives.
- Chitin: A completely different structural polysaccharide (containing nitrogen) found in fungal walls and arthropod exoskeletons.
#92 of 120
AJK 2019
Permalink
\( C_5H_{10}O_5 \) is the formula of ____.
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Pentose sugars follow the general monosaccharide empirical formula Cn(H2O)n.
Solution: Ribose sugar has the molecular formula C₅H₁₀O₅. (Deoxyribose lacks one oxygen atom, giving it the formula C₅H₁₀O₄).
#93 of 120
ETEA 2019
Permalink
Chitin is a:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Chitin is a modified, nitrogen-containing biological macromolecule.
Solution:- Chitin is a structural polysaccharide.
- Unlike standard carbohydrates, it is a polymer composed of N-acetylglucosamine monomers.
- It forms the structural backbone of fungal cell walls and the hard exoskeletons of arthropods (insects, crustaceans).
Why other options are incorrect:- Lipoproteins/Phospholipids: These are lipid-based structures related to transport and cell membranes.
- Glycoprotein: A protein with a small carbohydrate chain attached, completely structurally distinct from the pure carbohydrate polymer chitin.
#94 of 120
MDCAT 2019
Permalink
Most proteins are made up of:
A
20 types of amino acids
B
170 types of amino acids
C
16 types of amino acids
D
10 types of amino acids
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:The universal genetic code translates RNA into a very specific subset of biological monomers.
Solution:- While about 170 amino acids exist in nature, only about 25 are used as constituents in biological proteins.
- Of those 25, exactly 20 standard types of amino acids are directly encoded by the universal genetic code (DNA/RNA) and make up the overwhelming majority of nearly all cellular proteins across all domains of life.
Why other options are incorrect:- 170 represents the total found anywhere in tissues, not those used to build proteins. The numbers 16 and 10 have no biochemical significance here.
#95 of 120
MDCAT 2019
Permalink
The structure of a fibrous protein comprises of polypeptide chains in the form of:
C
Long strands or fibrils
D
Spherical or curled up ball
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:A protein's macroscopic structure perfectly dictates its physiological function (structure-function relationship).
Solution:- Fibrous proteins (like collagen, keratin, silk) function to provide immense tensile strength and structural support.
- To achieve this, their polypeptide chains do not fold into complex 3D shapes. Instead, they align closely in parallel, forming tough, extended long strands or fibrils.
Why other options are incorrect:- Spherical / curled up ball / cluster: These describe the highly folded nature of Globular proteins (enzymes, antibodies, hormones).
#96 of 120
MDCAT 2019
Permalink
In glycine, 'R' is ____.
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:The R-group (side chain) is the only variable part distinguishing one amino acid from another.
Solution:- Glycine is the absolute simplest and smallest of all 20 standard amino acids.
- Its unique 'R' variable group is simply a single Hydrogen atom (-H).
- Because its side chain is so small, glycine can fit into very tight spatial environments where other amino acids cannot.
Why other options are incorrect:- Methane/Ethane: These are independent hydrocarbon gases. (A methyl group -CH3 is found in Alanine).
- Fatty acid: A massive lipid monomer, entirely unrelated.
#97 of 120
AJK 2019
Permalink
Which type of bonds is required to maintain the alpha helix configuration of a protein?
D
Hydrophobic interactions
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:The delicate, repeating architecture of secondary structures is maintained by repeating weak interactions.
Solution:- The α-helix coils the polypeptide chain into a rigid cylinder.
- This specific spiral configuration is stabilized exclusively by repeating Hydrogen bonds forming vertically down the axis of the helix between the peptide backbone groups (C=O of one amino acid binding to the N-H of an amino acid four positions away).
Why other options are incorrect:- Disulfide, Ionic, and Hydrophobic bonds: These strictly mediate the large-scale folding of Tertiary and Quaternary structures by interacting between the distant R-groups, not the backbone.
#98 of 120
NUMS 2019
Permalink
The structure given below is the constituent part of:
$$ \text{H}_2\text{N} - \underset{\text{H}}{\overset{\text{R}}{\text{C}}} - \text{COOH} $$
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Identifying biological monomers from structural formulas.
Solution:- The given formula vividly depicts a central alpha-carbon atom bonded to an amino group (-NH2), a carboxyl acidic group (-COOH), a variable side chain (-R), and a hydrogen atom.
- This is the universal, defining backbone structure of an amino acid.
- Amino acids strictly polymerize to form Proteins.
Why other options are incorrect:- Lipids: Comprised of fatty acids and glycerol.
- Carbohydrates: Comprised of polyhydroxy aldehydes/ketones (monosaccharides).
- Vitamins: Highly varied small organic co-factors, lacking this specific uniform backbone.
#99 of 120
MDCAT 2019
Permalink
Lipids contain double amount of energy as compared to the same amount of carbohydrates due to the presence of:
A
Lower proportion of C-H bonds
B
Higher proportion of C-O bonds
C
Higher proportion of C-H bonds
D
Higher proportion of oxygen
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Biological energy yield is fundamentally determined by the oxidation state of the carbon atoms in a molecule.
Solution:- The chemical energy harvested during cellular respiration comes from stripping high-energy electrons away from non-polar Carbon-Hydrogen (C-H) bonds.
- Lipids (fatty acids) consist of massive, long hydrocarbon tails almost entirely composed of these C-H bonds, with very little oxygen present.
- Because they possess a vastly higher proportion of C-H bonds compared to carbohydrates (which are already partially oxidized with many C-O bonds), lipids yield more than double the energy upon complete oxidation (~9 kcal/g vs ~4 kcal/g).
Why other options are incorrect:- Higher proportion of C-O / Oxygen: This describes carbohydrates. Molecules with high oxygen content are already partially oxidized, meaning they have less potential energy left to release.
- Lower proportion of C-H bonds: The direct opposite of reality.
#100 of 120
AJK 2019
Permalink
Lipids are organic molecules which are insoluble in:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:The universal solvent rule: "Like dissolves like."
Solution:- Lipids are fundamentally defined by their predominantly non-polar, hydrophobic hydrocarbon structures.
- Water is a highly polar, hydrogen-bonding solvent.
- Because water energetically prefers to bond with itself rather than non-polar molecules (hydrophobic exclusion), lipids are famously insoluble in water.
Why other options are incorrect:- Alcohol, Ether, and Chloroform: These are classic non-polar or weakly polar organic solvents. Lipids readily dissolve in them.
#101 of 120
AJK 2019
Permalink
What type of linkage is formed when an alcohol and an acid react?
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Specific functional group reactions define the synthesis of biological polymers.
Solution:- When a carboxylic acid (such as a fatty acid) reacts with an alcohol (such as glycerol), a condensation reaction occurs.
- The resulting covalent linkage uniting the two molecules is specifically called an Ester bond (\(-C-O-C(=O)-\)), accompanied by the release of water.
- This is the fundamental reaction that builds triglycerides and other lipids.
Why other options are incorrect:- Peptide bond: Formed between an amino group and a carboxyl group (proteins).
- Glycosidic linkage: Formed between two hydroxyl (alcohol) groups (carbohydrates).
- Hydrogen bond: A weak intermolecular physical attraction, not a covalent reaction product.
#102 of 120
AJK 2019
Permalink
The head of phospholipid molecule is polar (hydrophilic) due to:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Phospholipids are amphipathic molecules, meaning they possess both a water-loving head and water-fearing tails.
Solution:- A phospholipid consists of a glycerol backbone attached to two non-polar fatty acid tails and one strongly polar head group.
- This head group derives its intense polarity and negative electrical charge from the Phosphate group (\(PO_4^{3-}\)).
- Because the phosphate is charged, it readily forms electrostatic interactions and hydrogen bonds with water, making the "head" completely hydrophilic.
Why other options are incorrect:- Fatty acids: Form the long, highly non-polar, hydrophobic tails.
- Carboxylic acid: These groups on the fatty acids are lost (converted to ester bonds) during synthesis, so they don't contribute to head polarity.
- Triacylglycerol: A completely different, fully non-polar storage fat molecule that lacks a phosphate entirely.
#103 of 120
NUMS 2019
Permalink
Which of the following are the most prominent part of cell membranes in living organisms?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:The physical boundary of every living cell on Earth relies on the spontaneous self-assembly of specific amphipathic molecules.
Solution:- Phospholipids are uniquely structured with a hydrophilic head and hydrophobic tails.
- When placed in an aqueous environment, they spontaneously arrange themselves tail-to-tail to form the lipid bilayer, effectively hiding their hydrophobic tails from water.
- This bilayer forms the primary, ubiquitous structural matrix (the most prominent part) of all plasma membranes across all domains of life.
Why other options are incorrect:- Acylglycerols (Triglycerides) & Waxes: Wholly non-polar molecules used primarily for energy storage and waterproofing, respectively; they cannot form a bilayer.
- Terpenoids: While some derivatives (like cholesterol) exist in membranes, they act as minor fluid-modifiers, not the prominent structural matrix itself.
#104 of 120
NUMS 2019
Permalink
Which of the following is the constituent of RNA molecule?
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Basic terminology of genetic macromolecules.
Solution:- The acronym RNA directly stands for Ribonucleic acid.
- Note: While the question phrasing "constituent of RNA molecule" is somewhat tautological and poorly worded in the original exam, "Ribonucleic acid" is the only option that correctly names the molecule itself, distinguishing it from DNA.
Why other options are incorrect:- Fatty acids / Ascorbic acid: Completely unrelated lipid and vitamin classes.
- Deoxyribonucleic acid: This is DNA, a distinctly different molecule featuring a different sugar and the base thymine.
#105 of 120
MDCAT 2018
Permalink
Glycosidic bond is formed by the:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Glycosidic bonds link simple sugars together via a dehydration synthesis reaction.
Solution:- When two monosaccharides bond to form a disaccharide, an -OH group from one sugar and an -H from the other sugar are excised.
- These excised atoms combine to form a water molecule (\(H_2O\)), which is expelled from the reaction site.
- Thus, the covalent O-glycosidic bond is formed precisely by the removal of water.
Why other options are incorrect:- Addition of water: This would describe hydrolysis (breaking the bond), not forming it.
- Removal/Addition of oxygen: Does not account for the hydrogen atoms involved in forming the water byproduct.
#106 of 120
MDCAT 2018
Permalink
Which of the following holds the alpha helix of protein in its place?
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:The structural stability of secondary shapes relies on extensive, repeating weak interactions.
Solution:- The α-helix is a right-handed coil where the backbone spirals around a central axis.
- This delicate geometric spiral is held tightly in place entirely by Hydrogen bonds.
- These bonds occur specifically between the slightly positive Hydrogen of an amino group (N-H) and the slightly negative Oxygen of a carboxyl group (C=O) located exactly four amino acids further down the chain.
Why other options are incorrect:- Disulphide bonds / R-group interactions: These strictly dictate the overall Tertiary (3D) folding pattern, not the local secondary helix.
#107 of 120
MDCAT 2018
Permalink
The number and sequence of amino acids along a polypeptide chain is called structure of a protein.
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:The hierarchical levels of protein structure begin with the basic genetic blueprint.
Solution:- The most basic foundational level is the Primary structure.
- It is defined strictly as the exact number, specific type, and linear sequence in which amino acids are strung together by covalent peptide bonds (directly dictated by mRNA).
Why other options are incorrect:- Secondary, Tertiary, Quaternary: These describe how that linear primary sequence bends, folds, and aggregates into three-dimensional space.
#108 of 120
PMC 2018
Permalink
Which of the following is an unsaturated fatty acid?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Knowing the common names and saturation status of major biological fatty acids is a standard requirement.
Solution:- Oleic acid (the primary component of olive oil) is an 18-carbon fatty acid containing exactly one double bond between carbons 9 and 10.
- Because of this double bond, it is classified as a mono-unsaturated fatty acid.
Why other options are incorrect:- Butyric acid (C4), Palmitic acid (C16), and Stearic acid (C18): These are all fully saturated fatty acids, containing absolutely zero carbon-carbon double bonds in their aliphatic chains.
#109 of 120
MDCAT 2017
Permalink
Which of the following type of carbohydrates has high molecular weight and is sparingly soluble in water?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:As carbohydrates increase in polymer chain length, their physical properties shift from small, sweet, soluble crystals to massive, tasteless, insoluble structural units.
Solution:- Polysaccharides (like starch, cellulose, and glycogen) are formed by hundreds or thousands of monosaccharide monomers.
- Because of their immense chain length and complex three-dimensional folding, they have exceptionally high molecular weights.
- This massive structure prevents water from easily forming hydration shells around them, making them sparingly soluble or entirely insoluble in water.
Why other options are incorrect:- Monosaccharides & Disaccharides: Have low molecular weights and are highly soluble in water due to exposed hydroxyl groups readily forming hydrogen bonds.
#110 of 120
MDCAT 2017
Permalink
____ are the major sites for the storage of glycogen in an animal's body.
A
Around thighs and belly
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Glycogen serves as the primary short-term biological energy buffer in vertebrates.
Solution:- Glycogen is abundantly synthesized and stored in liver cells (to regulate overall blood glucose levels) and skeletal muscle cells (to serve as an immediate local energy reserve during vigorous contraction).
Why other options are incorrect:- Around thighs, belly, and hips: These regions represent adipose tissue, which stores long-term energy as triglycerides (lipids), not glycogen.
- Kidneys: While capable of some metabolic functions, they are not the primary mass-storage sites for glycogen.
#111 of 120
MDCAT 2017
Permalink
The number of amino acids that have been found to occur in cells and tissues are:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:There is a vast difference between the total amino acids found in nature versus the specific few encoded by DNA to build proteins.
Solution:- Biochemists have identified approximately 170 different types of amino acids scattered throughout various cells and tissues in nature.
- Many of these serve independent metabolic functions (e.g., ornithine, citrulline) and are never incorporated into proteins.
Why other options are incorrect:- 20-25: This refers strictly to the "standard" proteinogenic amino acids that are used specifically as building blocks to synthesize cellular proteins, not the total number found in biological tissues.
#112 of 120
MDCAT 2017
Permalink
Backbone of amino acid comprises of:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:The polypeptide backbone forms a continuous, repeating structural chain along the length of a protein.
Solution:- Every single amino acid contains an amino group (nitrogen), an alpha-carbon, and a carboxyl carbon.
- When they bond linearly via peptide bonds, the continuous repeating sequence making up the unbranched structural "spine" of the protein is precisely N-C-C (or C-C-N).
Why other options are incorrect:- The individual -NH2 and -COOH groups represent the functional ends of a monomer, but the actual polymerized backbone is the repeating C-C-N sequence itself.
#113 of 120
MDCAT 2017
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If in lipids there is a higher proportion of unsaturated fatty acid, then it will be:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:The physical state of a lipid at room temperature is dictated by the chemical saturation of its hydrocarbon tails.
Solution:- Unsaturated fatty acids contain one or more carbon-carbon double bonds (\(C=C\)).
- These double bonds introduce rigid "kinks" or bends into the hydrocarbon chain, physically preventing the lipid molecules from packing tightly together.
- Because they cannot pack densely, the intermolecular forces remain weak, causing the lipid to exist as a liquid (Oil) at room temperature.
Why other options are incorrect:- Fats: Highly saturated lipids (no double bonds), allowing them to pack tightly and remain solid at room temperature (e.g., butter, lard).
- Waxes: Extreme long-chain solid lipids, used for waterproofing.
- Phenols: Aromatic organic compounds completely unrelated to triacylglycerols.
#114 of 120
MDCAT 2016
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The compounds which, on hydrolysis, yield polyhydroxy aldehyde or ketone subunits are:
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Chemical definition of a specific macromolecule class.
Solution:- By strict biochemical definition, Carbohydrates are either direct polyhydroxy aldehydes (aldoses) or polyhydroxy ketones (ketoses), or they are larger complex substances (like di- or polysaccharides) that yield these exact simple sugar subunits upon hydrolysis.
Why other options are incorrect:- Proteins: Yield amino acids upon hydrolysis.
- Lipids: Yield fatty acids and glycerol (or other alcohols).
- Polynucleotides: Yield nucleotides (sugar, phosphate, base).
#115 of 120
MDCAT 2016
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Secondary structure of protein is found in:
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Correct Key: Option B
Diagnostic Explanation
Concept:Proteins generally fall into two broad structural classes: Fibrous and Globular.
Solution:- Fibrous proteins exist as long, parallel strands or sheets, primarily relying on highly repetitive Secondary structure to provide immense tensile strength.
- Keratin (found in hair, nails, and feathers) is a classic fibrous protein dominated almost entirely by alpha-helical secondary structures wound together into supercoils.
Why other options are incorrect:- Trypsin (enzyme), Insulin & Glucagon (hormones): These are all Globular proteins, meaning they fold extensively into Tertiary structures to perform highly specific biochemical functions.
#116 of 120
MDCAT 2016
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Phosphodiester bond is:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:The nucleic acid backbone relies on bridging multiple atoms to link independent nucleotides together.
Solution:- A phosphodiester bond connects the 3' carbon of one sugar to the 5' carbon of the next sugar via a central phosphate group.
- Structurally, it forms two distinct ester linkages branching off the central phosphorus.
- The linear atomic sequence through this bridge is precisely: Carbon (from sugar 1) - Oxygen - Phosphorus - Oxygen - Carbon (from sugar 2).
- This is perfectly represented by the formula C-O-P-O-C.
Why other options are incorrect:- C-O-P / C-C-O-P: These represent only a single ester linkage (like attaching a phosphate to just one sugar), not the diester bridge linking two.
- P-O-C-P-O-C: Incorrect atomic repetition; a single phosphate (P) bridges the gap.
#117 of 120
MDCAT 2015
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Which molecular structure of enzyme is essential for activity of enzyme?
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:An enzyme must have a specific, complex three-dimensional shape (the active site) to bind to its substrate.
Solution:- The functional active site of an enzyme is formed when the linear polypeptide chain twists, bends, and folds back upon itself into a complex, 3D globular shape.
- This overall 3D folding pattern is the Tertiary structure. Without attaining at least the tertiary level, the active site physically does not exist, and the enzyme is utterly inactive.
Why other options are incorrect:- Primary/Secondary: These form a straight chain or simple spirals, lacking the 3D pocket required for catalysis.
- Quaternary: While some enzymes have multiple subunits, many enzymes function perfectly with just a single polypeptide chain in its tertiary state.
#118 of 120
MDCAT 2014
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The simplest monosaccharide containing keto group is:
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Correct Key: Option B
Diagnostic Explanation
Concept:Monosaccharides are polyhydroxy aldehydes or ketones. The simplest sugars are trioses, containing exactly three carbon atoms.
Solution:- There are two three-carbon sugars (trioses):
- Glyceraldehyde: Contains an aldehyde functional group (an aldotriose).
- Dihydroxyacetone: Contains a ketone functional group (a ketotriose).
- Therefore, the simplest possible monosaccharide with a keto group is Dihydroxyacetone.
Why other options are incorrect:- Glyceraldehyde: The simplest aldo-sugar, not keto.
- Ribose: A 5-carbon aldo-sugar.
- Glucose: A 6-carbon aldo-sugar.
#119 of 120
LUMHS 2014
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Which level of protein structure maintains the helix shape of enzymes?
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Protein architecture is divided into hierarchical levels based on folding patterns and bond interactions.
Solution:- The Secondary structure of a protein refers specifically to the localized, regular folding patterns of the polypeptide backbone.
- These folded geometries strictly take the form of either the alpha-helix or the beta-pleated sheet, maintained rigidly by hydrogen bonds forming between the N-H and C=O groups along the backbone.
- Note: While enzymes functionally rely on their overall 3D Tertiary shape, the specific 'helix shape' geometric component is entirely dictated and maintained by secondary structure.
Why other options are incorrect:- Primary: Defines the linear sequence of amino acids via peptide bonds.
- Tertiary: Defines overall 3D globular folding via R-group interactions.
- Quaternary: Defines multiple subunits binding together.
#120 of 120
KMDC 2014
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Enzymes are molecules of one of the following group of biomolecules. Mark the correct answer which can also be defined as a biological catalyst:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Biocatalysts lower activation energy to accelerate reactions necessary for life.
Solution:- The vast majority of enzymes (biological catalysts) are globular Proteins.
- Their complex, 3D folded amino acid structure creates a highly specific active site capable of binding substrates. (Note: A very small minority are catalytic RNAs called ribozymes, but protein is the primary class).
Why other options are incorrect:- Fats, carbohydrates, and vitamins do not possess the complex tertiary folding architectures required to form catalytic active sites. (Vitamins often act merely as co-enzymes assisting the main protein).
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