#1 of 143
SZABMU-2024-Reconduct
Middle lamella is composed of: (SZAMBU-2024-Reconduct)
A
Magnesium + sodium salts + pectin
B
Magnesium + calcium salts + pectin
C
Calcium + sodium salts + pectin
D
Magnesium + potassium salts + pectin
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Plant cells are glued together by a sticky extracellular layer.
Solution: The middle lamella is the first layer formed during cell division, acting as a cement between adjacent plant cells. It is primarily composed of sticky pectates, specifically calcium and magnesium salts of pectic acid (pectin).
Distractor Autopsy: Sodium and potassium are highly soluble monovalent cations and do not form the rigid, insoluble cross-links required for plant cell adhesion.
#2 of 143
SZABMU-2024-Reconduct
In which type of cells, cell wall is not present? (SZAMBU-2024-Reconduct)
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: The presence or absence of a cell wall is a fundamental characteristic dividing major kingdoms of life.
Solution: Liver cells (hepatocytes) are animal cells. Animal cells universally lack a rigid cell wall, utilizing only a flexible plasma membrane to allow for varied shapes and motility.
Distractor Autopsy: Plants (cellulose), Fungi (chitin), and Bacteria (peptidoglycan) all obligately possess cell walls.
#3 of 143
SZABMU-2024-Reconduct
The cells in our body are all genetically identical, apart from the: (SZAMBU-2024-Reconduct)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Meiosis introduces genetic variation and reduces chromosome number, distinguishing germline cells from somatic cells.
Solution: All somatic (body) cells are produced via mitosis and are genetically identical clones (diploid). However, reproductive cells (gametes like sperm and egg) undergo meiosis, making them haploid and genetically unique due to crossing over and independent assortment.
Distractor Autopsy: Muscle fibers and white blood cells are somatic cells and share the identical diploid genome of the organism (though B/T cells undergo genetic rearrangement, "reproductive cells" is the broad, fundamental answer expected here).
Plasma membrane is differentially permeable membrane due to the presence of: (KMU-2024)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: The baseline barrier property of the plasma membrane restricts the movement of most biological molecules.
Solution: The plasma membrane is differentially permeable primarily because of its continuous lipid bilayer (phospholipids). The hydrophobic fatty acid tails create a highly non-polar core that naturally repels ions and large polar molecules, restricting their passage.
Distractor Autopsy: While proteins provide specific pathways for molecules to cross, it is the lipid bilayer that establishes the fundamental restriction (differential permeability) in the first place.
Amoeba engulfs liquid food across its membrane by a process: (SZAMBU-2024)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Cells use specific vesicular mechanisms to ingest different states of matter.
Solution: When a cell like an Amoeba engulfs droplets of extracellular fluid (liquid food), the process is specifically called
pinocytosis (cell drinking). The membrane invaginates to form a small fluid-filled vesicle.
Distractor Autopsy: - Phagocytosis: Engulfing large solid particles.
- Endocytosis: A general umbrella term; pinocytosis is the more accurate, specific answer for liquids.
Which function cannot be attributed to plasma membrane lipids? (NUMS-2024)
A
Control of metabolic reaction across cell membrane
B
Maintaining cell membrane flexibility
C
Binding ligands for intracellular response
D
Recognition of cells having non-self-surface markers
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Lipids form the structural barrier of the membrane, while proteins perform active metabolic and signaling tasks.
Solution: The
control of metabolic reactions across the cell membrane (such as enzymatic activity or active ion pumping) is carried out by integral and peripheral membrane
proteins, not the lipids.
Distractor Autopsy: - Flexibility: Maintained by phospholipids and cholesterol.
- Recognition/Binding: Glycolipids (lipids with carb chains) act as antigens and receptors for ligands.
Which one is the function of plasma membrane proteins? (NUMS-2024)
A
Prevention of freezing during cold weather
B
Restrict entry of polar molecules
C
Movement of ions in and out of the cell
D
Maintenance of membrane flexibility
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Ions cannot cross the hydrophobic lipid bilayer on their own and require specialized tunnels.
Solution: A primary function of integral plasma membrane
proteins is to act as channels, carriers, and pumps to facilitate the
movement of ions (like $\text{Na}^+$, $\text{K}^+$, $\text{Ca}^{2+}$) in and out of the cell.
Distractor Autopsy: - Restricting polar molecules: Function of the lipid bilayer.
- Flexibility/Freezing prevention: Function of unsaturated fatty acid tails and cholesterol.
#8 of 143
SZABMU-2024-Reconduct
Choose the correct sequence for permeability of molecules across the plasma membrane: (SZAMBU-2024-Reconduct)
A
Water / Glucose > Lipids > Sodium
B
Sodium > Lipids > Water / Glucose
C
Lipids > Water / Glucose > Sodium
D
Sodium > Water / Glucose > Lipids
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The hydrophobic core of the lipid bilayer dictates permeability: non-polar > small polar > large polar > charged ions.
Solution: The correct sequence from most to least permeable is: Lipids (highly non-polar, pass easily) > Water / Glucose (small/large uncharged polar, pass slowly or need carriers) > Sodium (charged ion, cannot pass without a channel).
Distractor Autopsy: Any sequence placing Sodium (an ion with a hydration shell) as highly permeable is entirely incorrect.
The active mass movement of mitochondria in the cytoplasm is due to: (KMU-2024)
A
Endoplasmic streaming movements
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Organelles do not propel themselves; they are carried by the flow of the cytoplasm.
Solution: Cyclosis (or cytoplasmic streaming) is the active, continuous circular movement of the cytoplasm driven by actin microfilaments. This movement sweeps organelles like mitochondria and chloroplasts around the cell to distribute nutrients and oxygen evenly.
Distractor Autopsy: Endoplasmic streaming is not a standard biological term. The Golgi and tRNA have no locomotive function.
The nucleus takes dyes due to the presence of: (UHS-2024)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The word "chromosome" literally translates to "colored body" (chroma = color, soma = body).
Solution: The nucleus stains deeply with basic biological dyes (like hematoxylin or methylene blue) due to the high concentration of negatively charged nucleic acids in the chromatin (DNA wrapped around histone proteins).
Distractor Autopsy: Lipids do not bind basic dyes well. Thylakoids are in chloroplasts. Metal ions are not the primary target of nuclear stains.
Chromosome is typically made up from a combination of: (KMU-2024)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: To fit two meters of DNA into a microscopic nucleus, it must be intricately spooled around structural supports.
Solution: A eukaryotic chromosome is a complex of nucleic acid and protein called chromatin. It is composed primarily of a long, continuous molecule of DNA tightly wrapped around octamers of basic histone proteins.
Distractor Autopsy: RNA is transcribed from DNA but does not form the permanent structural backbone of the chromosome. Lipids are not found in chromosomes.
Where are spindle fibres attached during cell division on a chromosome? (KMU-2024)
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: Accurate segregation of chromosomes requires a strong, centralized physical anchor point for motor proteins.
Solution: During mitosis and meiosis, spindle fibers (microtubules) attach to a specialized protein complex called the kinetochore, which is assembled at the highly constricted region of the chromosome known as the centromere.
Distractor Autopsy: Telomeres are the protective caps at the ends of chromosomes. Histones are the spools for DNA. The nucleolus is a nuclear organelle.
The exchange of materials between nucleus and cytoplasm takes place through: (SZAMBU-2024)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: The nuclear envelope is a double membrane that requires gated channels to allow macromolecules to enter and exit.
Solution: The nuclear envelope is punctuated by large protein complexes called nuclear pores. These pores strictly regulate the exchange of materials, allowing RNA and ribosomal subunits to exit into the cytoplasm, and necessary proteins (like polymerases) to enter the nucleus.
Distractor Autopsy: The nucleoplasm is the fluid inside. The nuclear lamina provides structural support. The nucleolus synthesizes rRNA.
Which organelle contributes towards steroid production? (KMU-2024)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Steroids are a class of lipids derived from cholesterol, requiring specific lipid-synthesizing enzymes.
Solution: The Smooth Endoplasmic Reticulum contains the embedded enzymes necessary for lipid metabolism, making it the primary organelle responsible for the synthesis of cholesterol and steroid hormones (like testosterone and estrogen).
Distractor Autopsy: Ribosomes make proteins. Lysosomes break down waste. The Golgi modifies and packages proteins/lipids but does not synthesize the steroid backbone itself.
Which of the following is the function of Golgi Complex? (UHS-2024)
B
Intracellular digestion
C
Processing of cell secretions
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Cellular products meant for export must be refined and sorted.
Solution: The primary function of the Golgi Complex is the processing, sorting, and packaging of cell secretions. It receives proteins from the RER, modifies them (e.g., adding carbohydrates to make glycoproteins), and buds them off in secretory vesicles for exocytosis.
Distractor Autopsy: Autophagy, intracellular digestion, and autolysis are all strictly the destructive functions of the lysosome.
Follow the route of pepsinogen secreted by zymogen cells: (NUMS-2024)
A
SER → RER → Golgi complex → Secretory vesicles
B
RER → SER → Golgi complex → Secretory vesicles
C
SER → Mitochondria → Golgi complex → Secretory vesicles
D
Golgi complex → RER → SER → Secretory vesicles
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The endomembrane system operates as a sequential assembly and shipping line for proteins.
Solution: Pepsinogen is a protein. Its correct secretory pathway is:
1. Synthesized on ribosomes of the Rough ER (RER).
2. Transitions through the Smooth ER (SER) where transport vesicles bud off.
3. Received and processed by the Golgi complex.
4. Packaged into Secretory vesicles that fuse with the plasma membrane.
Distractor Autopsy: Proteins are not synthesized by the SER, so starting there is incorrect. The Golgi is the final processor, not the starting point.
#17 of 143
SZABMU-2024-Reconduct
Cristae in mitochondria serve as a site for: (SZAMBU-2024-Reconduct)
C
Electron transport chain
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The folded inner membrane of the mitochondria maximizes surface area for ATP production.
Solution: The cristae (infoldings of the inner mitochondrial membrane) are studded with the protein complexes that make up the Electron transport chain (ETC) and ATP synthase. This is where oxidative phosphorylation occurs.
Distractor Autopsy: Glycolysis occurs in the cytoplasm. The Calvin cycle and photophosphorylation occur in the chloroplast.
#18 of 143
SZABMU-2024-Reconduct
Golgi complex is responsible for: (SZAMBU-2024-Reconduct)
B
Detoxification of alcohol
C
Processing of cell secretions
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The Golgi apparatus is the cell's post office.
Solution: The primary role of the Golgi complex is the processing of cell secretions. It receives immature proteins and lipids, modifies them chemically, sorts them, and packages them into vesicles for delivery to the plasma membrane or other organelles.
Distractor Autopsy: Protein synthesis = Ribosomes. Detoxification = Smooth ER / Peroxisomes. Glucose oxidation = Mitochondria.
The lysosomes found in eukaryotes contain: (KMU-2024)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Lysosomes utilize water to break chemical bonds in complex macromolecules.
Solution: Lysosomes contain a powerful arsenal of roughly 40 different acid hydrolases. These hydrolytic enzymes (like proteases, lipases, nucleases) function optimally at an acidic pH to digest cellular waste and engulfed pathogens.
Distractor Autopsy: Oxidative enzymes (which produce hydrogen peroxide) are found in peroxisomes. Mitotic/meiotic enzymes relate to cell division in the nucleus.
Tay-Sach's is related to the malfunctioning of which of the following organelle? (SZAMBU-2024)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Genetic absence of specific degradative enzymes leads to lethal cellular hoarding.
Solution: Tay-Sachs is a fatal genetic disorder caused by the malfunction of lysosomes. Specifically, a mutation causes the absence of the lysosomal enzyme hexosaminidase A, leading to a toxic buildup of lipids in the neurons of the brain.
Distractor Autopsy: Glyoxysomes break down fatty acids in plant seeds. ER and Golgi are not the primary sites of terminal macromolecule degradation.
#21 of 143
SZABMU-2024-Reconduct
Which enzyme is missing in the patient of Tay-Sach's disease? (SZAMBU-2024-Reconduct)
A
Carbohydrate digesting enzyme
B
Protein digesting enzyme
D
Fatty acid digesting enzyme
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Tay-Sachs targets the lipid-rich environment of the central nervous system.
Solution: The specific enzyme missing in Tay-Sachs disease is Hexosaminidase A, which is a lipid digesting enzyme. Without it, complex lipids called gangliosides accumulate to toxic levels in brain cells, causing severe neurological decline.
Distractor Autopsy: While proteins and carbohydrates are digested by other lysosomal enzymes (like proteases and glycosidases), Tay-Sachs is explicitly a lipid storage disorder.
#22 of 143
SZABMU-2024-Reconduct
Which one of the following describes best the autophagy? (SZAMBU-2024-Reconduct)
A
Intracellular food digestion
B
Decomposition of hydrogen peroxide
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Cells must continually clean house by recycling their own damaged components.
Solution: Autophagy literally translates from Greek as "self-eating" (auto = self, phagy = eating). It is the process by which a cell uses its lysosomes to enclose, digest, and recycle its own damaged organelles (like old mitochondria) or macromolecules.
Distractor Autopsy: Intracellular food digestion is heterophagy. Disintegration of the entire cell is autolysis. Decomposition of hydrogen peroxide is the job of peroxisomes.
Chloroplast are membrane bound bodies containing: (UHS-2024)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Plastids are categorized based on the specific compounds they synthesize and store.
Solution: Chloroplasts are a specific type of chromoplast (colored plastid) that fundamentally contain photosynthetic
pigments—primarily green chlorophyll, along with accessory pigments like carotenoids, essential for capturing solar energy.
Distractor Autopsy: - Linear ds-DNA: Chloroplast DNA is circular, not linear.
- Cristae: Found in mitochondria.
- Cisternae: Found in ER/Golgi.
Which of the following type of plastids is involved in dispersal of seed and pollination? (SZAMBU-2024)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Evolutionary biology relies on visual signaling between plants and animals for reproduction.
Solution: Chromoplasts synthesize and store brightly colored pigments (reds, oranges, yellows). By coloring flower petals and ripe fruits, they attract insects for pollination and animals for fruit consumption and subsequent seed dispersal.
Distractor Autopsy: Chloroplasts are for photosynthesis (green). Leucoplasts and amyloplasts are colorless storage plastids found in roots and underground stems.
Which cytoplasmic organelles make their own proteins? (KMU-2024)
D
Smooth endoplasmic reticulum
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The endosymbiotic theory explains the partial autonomy of certain energy-converting organelles.
Solution: Mitochondria (and chloroplasts) contain their own circular DNA and 70S ribosomes. This allows them to transcribe their own mRNA and translate it into a portion of the proteins they require to function, making them semi-autonomous.
Distractor Autopsy: The Golgi and SER lack ribosomes and DNA. Chromosomes are in the nucleus, not the cytoplasm, and do not "make" proteins (they store the code).
In the inner membrane of mitochondria which has many folds called cristae, there are granular particles called: (SZAMBU-2024)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The morphological appearance of the inner mitochondrial membrane under electron microscopy reveals tiny, stalked structures.
Solution: The cristae are studded with granular, lollipop-shaped particles known as $F0$-$F1$ particles, which are the enzyme complexes known as ATP Synthetase (or ATP synthase). These are responsible for phosphorylating ADP into ATP.
Distractor Autopsy: Cytochrome c and Ubiquinone are electron carriers, but they do not form large, granular particles visible on the cristae. Porins are on the outer membrane.
#27 of 143
SZABMU-2024-Reconduct
A group of ribosomes attached to mRNA is known as polysome and the attachment is controlled by: (SZAMBU-2024-Reconduct)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: The structural integrity of the ribosome depends on specific divalent cations.
Solution: The two subunits (large and small) of a ribosome only associate to form a functional translation complex on an mRNA strand in the presence of adequate concentrations of magnesium ions, \(\text{Mg}^{+2}\).
Distractor Autopsy: Sodium, Calcium, and Potassium are vital for electrical signaling and muscle contraction, but do not mediate ribosomal subunit joining.
The organelles found only at seeding stage in oil seed plants are: (UHS-2024)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Germinating seeds need a way to convert stored fats into usable sugars before they can photosynthesize.
Solution: Glyoxysomes are specialized plant microbodies found transiently during the seeding/germination stage in oil-rich seeds (like castor beans). They contain enzymes of the glyoxylate cycle, which convert stored fatty acids directly into carbohydrates to fuel early seedling growth.
Distractor Autopsy: Peroxisomes, vacuoles, and general microbodies are found in many cell types across all stages of plant and animal life.
A lizard detaches its tail when attacked by a predator. This is an example of: (NUMS-2024)
D
Intracellular digestion
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Programmed destruction of tissue can serve as a survival mechanism at the organismal level.
Solution: When a lizard sheds its tail (autotomy), the physical detachment at the fracture plane involves rapid, programmed cellular destruction. At the cellular level, this massive destruction of tissue is facilitated by autolysis, where lysosomes burst and digest the cells at the detachment site to allow a clean break.
Distractor Autopsy: Autophagy is internal recycling (the cell survives). Phagocytosis and intracellular digestion involve eating external food.
Choose the correct set of characteristics for intermediate filaments: (NUMS-2024)
A
Diameter: 8-10nm, Composition: Tubulin, Function: Muscle contraction
B
Diameter: 0.2-25μm, Composition: Vimentin, Function: Cilia, flagella
C
Diameter: 8-10nm, Composition: Vimentin, Function: Mechanical support
D
Diameter: 7nm, Composition: Tubulin, Function: Cyclosis
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The cytoskeleton consists of three distinct filament types categorized by diameter and protein composition.
Solution: Intermediate filaments have a diameter of 8-10nm (between microfilaments at 7nm and microtubules at 25nm). They are composed of various robust proteins (such as keratin or vimentin) and their primary function is to provide tensile strength and mechanical support to the cell.
Distractor Autopsy: Tubulin forms microtubules (cilia/flagella). Actin forms 7nm microfilaments (muscle contraction/cyclosis).
Secondary cell wall in plants is present: (NUMS-2023)
A
In between two primary cell walls
B
Between the primary cell wall and plasma membrane
C
Inner to plasma membrane
D
Outer to primary cell wall
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: As a plant cell matures, it may lay down additional, stronger wall layers inward from the original wall.
Solution: The primary cell wall is secreted first. Once the cell stops growing, a thicker, rigid secondary cell wall is secreted by the plasma membrane underneath the primary wall. Thus, it is located between the primary cell wall and the plasma membrane.
Distractor Autopsy: The middle lamella lies outside the primary wall (between adjacent cells). Nothing is structural "inner to the plasma membrane" except the cytoskeleton.
What distinguishes prokaryotic cell wall from fungal cell wall? (NUMS-2023)
A
Prokaryotic cell wall contains silica
B
Prokaryotic cell wall contains peptidoglycan
C
Prokaryotic cell wall contains cutin
D
Prokaryotic cell wall contains cellulose
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Chemical composition of the cell wall provides structural distinction between biological kingdoms.
Solution: A defining feature is that the prokaryotic (bacterial) cell wall is composed of peptidoglycan, a unique matrix of sugars and amino acids. In stark contrast, the fungal cell wall is composed of chitin.
Distractor Autopsy: Cellulose is found in plants. Silica is found in diatoms (protists). Cutin is a plant lipid.
Which of the following is absent from membrane of prokaryotes? (NUMS-2023)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Prokaryotic and eukaryotic plasma membranes share a basic lipid bilayer but differ in their stabilizing molecules.
Solution: Cholesterol is a sterol exclusively found in the cell membranes of eukaryotes (particularly animals), acting as a fluidity buffer. Prokaryotic membranes lack cholesterol (some use hopanoids instead).
Distractor Autopsy: Both prokaryotes and eukaryotes utilize phospholipids as their primary membrane matrix, along with glycoproteins and glycolipids for varied functions.
Cell membrane also contain ____ through which movement of substances take place by active and passive transport. (NUMS-2023)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Carrier proteins undergo conformational change to transport specific solutes across the cell membrane by both passive transport (facilitated diffusion) and active transport.
Solution: Carrier Proteins (Option B) are membrane transport proteins that facilitate both active transport (e.g., Na+/K+-ATPase pump) and passive transport (facilitated diffusion, e.g., GLUT glucose transporters). In contrast, pores or channel proteins only mediate passive diffusion along electrochemical gradients and cannot perform active transport.
According to the fluid mosaic model of cell membrane, which zone is embedded inside? (NUMS-2023)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The amphipathic nature of phospholipids dictates membrane self-assembly in aqueous environments.
Solution: In the lipid bilayer, the non-polar fatty acid tails turn away from the watery intra- and extracellular fluids, pointing towards each other. This creates a deeply embedded hydrophobic (water-fearing) core.
Distractor Autopsy: The hydrophilic (water-loving) phosphate heads face outward towards the aqueous environment.
Which part of plasma membrane controls the fluidity of the membrane? (SZABMU-2023)
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: Membrane fluidity is essential for cell function, transport, and cell division.
Solution: The lipid component—specifically the ratio of saturated (straight) to unsaturated (kinked) fatty acid tails of phospholipids, along with intercalated cholesterol molecules—directly controls how rigidly or fluidly the membrane behaves at varying temperatures.
Distractor Autopsy: Proteins function in transport and signaling. Carbohydrates (on glycoproteins/glycolipids) function in cell-cell recognition.
Many enzymes are secreted in inactive form to protect: (SZABMU-2023)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Cells synthesize dangerous digestive enzymes that could destroy their own architecture if activated prematurely.
Solution: Powerful proteolytic enzymes (like pepsinogen) are secreted in an inactive zymogen form. This prevents them from digesting the cell membrane and internal proteins of the very cell that produced them during transport and exocytosis.
Distractor Autopsy: While DNA and mitochondria are vital, the immediate structure exposed to a secreted enzyme during the exocytosis process is the cell membrane.
Where do phospholipids arrange themselves in a cell? (ETEA-2023)
A
Inside the plasma membrane
D
Inside the mitochondrial matrix
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Phospholipids are the fundamental building blocks of all biological barriers.
Solution: Because they are amphipathic, phospholipids spontaneously assemble into a continuous bilayer to form the plasma membrane (and the membranes of internal organelles), creating a boundary between the cell and its environment.
Distractor Autopsy: They do not freely float in the cytoplasm, nucleus, or mitochondrial matrix; they are structurally bound to the membranes themselves.
#39 of 143
ETEA-2023 Retake
An additional covering surrounds the cell wall of some bacteria that either prevents the bacteria from being phagocytosed by host cells or helps them to make biofilm, which of the following term used for the covering? (ETEA-2023 Retake)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Pathogenic bacteria often possess external virulence factors to evade the host immune system.
Solution: The capsule is a tightly bound, thick, sticky outer layer of polysaccharides surrounding the cell wall of many bacteria. It is famously known for hiding the bacteria from host macrophages (preventing phagocytosis) and facilitating adherence for biofilms.
Distractor Autopsy: Slime layers are similar but much looser and easily washed off. Spores are dormant internal structures for survival, not external coverings.
#40 of 143
ETEA-2023 Retake
____ regulates the selective permeability of the plasma membrane, allowing movement of molecules according to the needs of the cells. (ETEA-2023 Retake)
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: While lipids provide the barrier, proteins act as the selective gates.
Solution: Membrane proteins (acting as channels, carriers, and pumps) dynamically regulate the selective permeability of the membrane. They selectively facilitate the movement of specific ions and polar molecules into or out of the cell based on cellular requirements.
Distractor Autopsy: Cholesterol regulates fluidity. Carbohydrates handle cell recognition. The lipid bilayer itself is a non-selective barrier to polar substances.
Peripheral parts of cell are often like a: (SZABMU-2023)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The cytoplasm exhibits different physical states depending on its location and cytoskeletal density.
Solution: The cytoplasm is a colloidal system. The outer, peripheral part of the cell (ectoplasm) just beneath the plasma membrane is dense and viscous, behaving like a semi-solid gel. This provides structural support and helps maintain cell shape.
Distractor Autopsy: The inner region (endoplasm) is more fluid and behaves like a sol to facilitate organelle movement and diffusion.
The cytoplasm contain/s: (ETEA-2023)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The cytoplasm is a complex matrix containing both living machinery and non-living materials.
Solution: The cytoplasm is a highly heterogeneous mixture. It contains metabolically active cell organelles (mitochondria, ribosomes), as well as non-living cell inclusions which include both storage products (glycogen, lipid droplets) and insoluble wastes.
Distractor Autopsy: Any option claiming "only" is incorrect because the cytoplasm must simultaneously hold all three components for the cell to function and survive.
#43 of 143
ETEA-2023 Retake
Function of the nucleus is to form: (ETEA-2023 Retake)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The nucleus is not just a storage vault; it is the active site of transcription.
Solution: A primary synthetic function of the nucleus (specifically the nucleolus region) is to transcribe and form ribosomal RNA (rRNA). This rRNA is then assembled into ribosome subunits, which are exported to the cytoplasm.
Distractor Autopsy: Chromosomes are housed within the nucleus, not "formed" as a product. The nuclear envelope bounds the nucleus, and the cytoplasm surrounds it.
Sarcoplasmic reticulum for muscle fibers is mainly responsible for: (NUMS-2023)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Muscle contraction is tightly regulated by intracellular ion concentrations.
Solution: In muscle cells, the smooth endoplasmic reticulum is highly specialized and renamed the sarcoplasmic reticulum. Its primary role is the active sequestration and calcium storage (\(\text{Ca}^{2+}\)). Upon nervous stimulation, it releases calcium to trigger muscle contraction.
Distractor Autopsy: While standard SER handles lipid metabolism, the sarcoplasmic reticulum is evolutionarily adapted specifically for calcium handling.
Select the one which is not a function of smooth endoplasmic reticulum? (NUMS-2023)
A
Processing of glycoproteins
B
Transmission of impulses
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Cellular organelles have distinct, non-overlapping post-translational duties.
Solution: The processing of glycoproteins (the addition and modification of carbohydrate chains on proteins) is strictly the domain of the Golgi apparatus (and begins in the RER), not the Smooth ER.
Distractor Autopsy: The SER is responsible for lipid metabolism, detoxifying drugs, transporting materials (via transition vesicles), and transmitting impulses (via calcium release in muscle cells).
Lipid synthesis occurs in which one of the following organelles of the cell? (ETEA-2023)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The endomembrane system compartmentalizes macromolecule production.
Solution: Lipid synthesis (including phospholipids, oils, and steroid hormones) primarily occurs in the Smooth Endoplasmic Reticulum, which houses the necessary embedded metabolic enzymes.
Distractor Autopsy: Ribosomes synthesize proteins. Mitochondria synthesize ATP. Golgi bodies package and modify existing proteins/lipids.
Outer membrane of mitochondria and chloroplast resembles as both are: (SZABMU-2023)
A
Freely permeable to small molecules
C
Freely permeable to large molecules
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: The outer boundary of endosymbiotic organelles is designed to allow easy access for cellular metabolites.
Solution: The outer membranes of both mitochondria and chloroplasts contain abundant transport proteins called porins. These create large aqueous channels making the outer membrane freely permeable to small molecules and ions.
Distractor Autopsy: The inner membrane is highly impermeable/semipermeable to strictly regulate proton gradients. Neither is permeable to very large macromolecules without specific translocators.
In mitochondria, ATP synthase is located on its: (SZABMU-2023)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Chemiosmosis requires a membrane barrier to establish a proton gradient.
Solution: ATP synthase is an enzyme complex physically embedded in the inner mitochondrial membrane (on the cristae). As protons flow back into the matrix through this enzyme, it uses the kinetic energy to phosphorylate ADP into ATP.
Distractor Autopsy: The matrix contains the Krebs cycle enzymes. The outer membrane is too porous to maintain a proton gradient.
The folds of inner mitochondrial membrane of mitochondria are called: (NUMS-2023)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Membrane folding increases surface area for maximum metabolic output.
Solution: The inner membrane of the mitochondrion folds inward to form structures known as
cristae. These folds pack a massive amount of electron transport chain proteins and ATP synthase into a small volume.
Distractor Autopsy: - Cisternae: Flat sacs in the Golgi/ER.
- Mesosomes: Membrane folds in bacteria.
Which of the following organelle is regarded as self-replicating organelle? (ETEA-2023)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Some organelles retain evolutionary remnants of a free-living bacterial past.
Solution: Mitochondria (and chloroplasts) are considered semi-autonomous, self-replicating organelles. They possess their own circular DNA and ribosomes, allowing them to divide independently of the cell's main nucleus via a process similar to binary fission.
Distractor Autopsy: The ER, Golgi bodies, and vacuoles are produced and regulated entirely by the main endomembrane system of the cell and cannot replicate themselves.
Mitochondria is usually absent in: (ETEA-2023)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Mammalian red blood cells undergo extreme specialization to maximize oxygen transport.
Solution: During maturation, mammalian red blood cells (mature RBCs) eject their nucleus and degrade all internal organelles, including mitochondria. This frees up maximum space for hemoglobin and prevents the RBC from consuming the oxygen it is meant to deliver (they rely solely on anaerobic glycolysis).
Distractor Autopsy: Muscle and cardiac cells have extremely high energy demands and are packed with abundant mitochondria.
Proteins and lipids are modified into glycolipids and glycoproteins by which cell organelles? (UHS-2023)
A
Smooth endoplasmic reticulum
C
Rough endoplasmic reticulum
D
Ribosomes and chromosomes
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Cellular products must be "tagged" and modified before being sent to their final destinations.
Solution: The Golgi complex acts as the cell's post office. It receives basic proteins and lipids from the ER and adds carbohydrate chains to them (glycosylation), modifying them into functional glycoproteins and glycolipids before secretion or membrane integration.
Distractor Autopsy: The Rough and Smooth ER synthesize the raw proteins and lipids, respectively, but the extensive final modification into glycolipids/proteins is the hallmark of the Golgi.
____ consists of units called dictyosomes. (ETEA-2023)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Plant biology sometimes uses specific terminology for universal organelles based on structural variations.
Solution: The Golgi complex in plant cells is often not a single, continuous structure but consists of scattered, individual stacks of membrane-bound vesicles and cisternae. These individual stacks are specifically called dictyosomes.
Distractor Autopsy: Lysosomes and glyoxysomes are single vesicular bodies. Ribosomes are non-membranous protein clusters.
Which of the following is not the function of lysosomes? (SZABMU-2023)
B
Intracellular digestion
C
Processing of cell secretions
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Lysosomes are strictly the waste disposal and recycling centers of the cell, not the manufacturing or shipping centers.
Solution: The processing of cell secretions (modifying, sorting, and packaging proteins/lipids for export) is the specific function of the Golgi apparatus. Lysosomes do not process cell secretions.
Distractor Autopsy: Lysosomes are responsible for intracellular digestion (breaking down food), autophagy (recycling old organelles), and autolysis (programmed cell death/self-destruction).
____ are spherical sacs, surrounded by a single membrane and contain hydrolytic enzymes. (NUMS-2023)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Cellular digestion must be compartmentalized to protect the rest of the cell from damage.
Solution: Lysosomes fit this exact morphological and functional description. They are single-membrane bound vesicles (spherical sacs) packed with acidic hydrolytic enzymes capable of breaking down all biological polymers.
Distractor Autopsy: Golgi bodies are flattened stacks (cisternae). Mitochondria and chloroplasts are double-membrane structures.
Tay-Sach's disease particularly results from the malfunctioning of: (ETEA-2023)
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: Genetic defects in organelle enzymes lead to toxic buildup of substrates within the cell.
Solution: Tay-Sachs disease is a classic lysosomal storage disorder. It results from a genetic mutation that causes a severe deficiency in hexosaminidase A, a specific lipid-digesting enzyme located inside lysosomes. This causes toxic levels of lipids (gangliosides) to accumulate in brain cells.
Distractor Autopsy: Malfunctioning of the nucleus (DNA), cell membrane, or vacuole does not directly cause the specific enzymatic lipid buildup characteristic of Tay-Sachs.
#57 of 143
ETEA-2023 Retake
Storage diseases are caused by the excessive accumulation of substances within the cell, due to defects (mutations) in one of the ____ enzymes. (ETEA-2023 Retake)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Without cellular recycling machinery, waste products build up and eventually kill the cell.
Solution: "Storage diseases" (like Tay-Sachs, Pompe, and Gaucher disease) are caused by congenital defects in specific lysosomal hydrolytic enzymes. When the lysosome cannot break down a particular macromolecule, it accumulates excessively, swelling the lysosome and damaging the cell.
Distractor Autopsy: Lipase, amylase, and lyases are specific classes of enzymes, but storage diseases are broadly classified by the organelle that fails (the lysosome).
Pollination is facilitated by: (NUMS-2023)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Plants utilize visual cues to attract animal and insect pollinators to their reproductive organs.
Solution: Chromoplasts are plastids that synthesize and store pigments (like carotenoids and xanthophylls) that impart bright red, orange, and yellow colors to flower petals and fruits. These bright colors attract insects and birds, thereby facilitating pollination and seed dispersal.
Distractor Autopsy: Chloroplasts provide green color (photosynthesis). Amyloplasts and leucoplasts are colorless and store starch.
The process of photophosphorylation takes place in: (ETEA-2023)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Converting solar energy into chemical energy requires specialized photosynthetic machinery.
Solution: Photophosphorylation is the synthesis of ATP using light energy. This process occurs strictly on the thylakoid membranes located inside the chloroplast.
Distractor Autopsy: The nucleus and nucleolus handle genetics. Golgi bodies handle protein packaging. None of these contain chlorophyll or photosystems.
#60 of 143
ETEA-2023 Retake
Which is the factory for the synthesis of sugar in autotrophic eukaryotes? (ETEA-2023 Retake)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Autotrophs fix inorganic carbon into organic sugar using light energy.
Solution: In eukaryotic plants and algae, the chloroplast is the site of both the light-dependent reactions and the light-independent reactions (Calvin cycle). The Calvin cycle acts as the "factory" that utilizes ATP, NADPH, and $\text{CO}_2$ to synthesize sugars (G3P/glucose).
Distractor Autopsy: Mitochondria break down sugar. Amyloplasts store sugar as starch. Ribosomes make proteins.
The membrane separating the vacuole from cytoplasm is called: (SZABMU-2023)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The plant vacuole requires a highly specialized boundary to manage rapid water influx and ion storage.
Solution: The specific biological term for the single, selectively permeable membrane that surrounds the central vacuole in a plant cell is the tonoplast.
Distractor Autopsy: While "vacuolar membrane" is descriptive, "tonoplast" is the exact terminological requirement for this level of biology. Cristae and cisternae are folds of the mitochondria and ER/Golgi, respectively.
Tonoplast is the membrane separating: (NUMS-2023)
A
Cytoplasm and nucleoplasm
B
Vacuole and nucleoplasm
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Understanding the physical location of the tonoplast defines its function in maintaining cell turgor.
Solution: The tonoplast bounds the large central vacuole, physically and chemically separating the aqueous contents of the vacuole (cell sap) from the surrounding cellular cytoplasm (cytosol).
Distractor Autopsy: The nuclear envelope separates the cytoplasm and nucleoplasm. The chloroplast envelope separates the cytoplasm and stroma.
Cell wall of prokaryotic cell is composed of: (UHS-2023)
B
Carbohydrates & Proteins
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The bacterial cell wall requires a unique cross-linked structure for immense tensile strength.
Solution: The prokaryotic (bacterial) cell wall is made of peptidoglycan (murein). "Peptido-" refers to short chains of amino acids (proteins/peptides), and "-glycan" refers to long sugar chains (carbohydrates). Thus, it is a complex of both.
Distractor Autopsy: Options listing only carbohydrates (like plant cellulose) or only proteins ignore the essential cross-linked nature of peptidoglycan.
Cyclosis and amoeboid movements are due to: (UHS-2023)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Different elements of the cytoskeleton are responsible for different types of cellular movement.
Solution: Microfilaments are extremely thin, flexible fibers made of the protein actin. They are directly responsible for cellular movements involving the plasma membrane and cytoplasm, such as amoeboid movement (pseudopodia), muscle contraction, and cyclosis (cytoplasmic streaming).
Distractor Autopsy: Microtubules (tubulin) are rigid and handle flagella/cilia and spindle fibers. Intermediate filaments provide static structural tension, not movement.
Each centriole is composed of ____ microtubules. (NUMS-2023)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Centrioles have a highly conserved, rigid geometric structure across all animal cells.
Solution: A single centriole is a short cylinder composed of exactly nine triplets of microtubules arranged in a ring (a $9+0$ arrangement).
Distractor Autopsy: Any other number (seven, five, eleven) violates the conserved $9+0$ microtubule organizing structure found in nature.
#66 of 143
ETEA-2023 Retake
Cell death due to tissue damage is called? (ETEA-2023 Retake)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: There are two primary pathways for cell death: one is planned, the other is accidental and messy.
Solution: Necrosis is the uncontrolled, premature death of cells in living tissue due to external factors like trauma, infection, toxins, or lack of oxygen (tissue damage). The cells swell and burst, causing inflammation.
Distractor Autopsy: Apoptosis is neat, programmed cell death (suicide). Cancer is uncontrolled cell growth, and metastasis is the spread of that cancer.
Cell wall may be absent in which of the following? (UHS-2022)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: While most prokaryotes have cell walls, there are notable evolutionary exceptions that lack them entirely.
Solution: Plants, algae, and fungi universally possess cell walls. However, certain bacteria (like genus Mycoplasma) and some archaea (like Thermoplasma) naturally lack a cell wall.
Distractor Autopsy: Any pairing containing plants, algae, or fungi is incorrect because those kingdoms are defined by the obligatory presence of a cell wall.
The cell wall of bacteria is made up of: (UHS-2022)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Different domains of life utilize distinct biochemical polymers for their cell walls.
Solution: The bacterial cell wall is primarily composed of peptidoglycan, also known as
murein. It consists of sugars cross-linked by short peptides.
Distractor Autopsy: - Cellulose: Found in plant and algal cell walls.
- Chitin: Found in fungal cell walls and arthropod exoskeletons.
Which of the following is correct for cell wall? (NUMS-2022)
C
Differentially permeable
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: The cell wall provides structural support but does not strictly regulate the passage of most small molecules and water.
Solution: Unlike the cell membrane, the primary cell wall is highly porous and fully permeable to water and most dissolved solutes.
Distractor Autopsy: Semi-permeable and differentially permeable are terms specifically reserved for the plasma membrane, which actively and passively selects what enters or exits the cell.
Chemically, cell wall of fungi is made up of: (SZABMU-2022)
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: Fungi possess a unique cell wall composition that distinguishes them from plants and bacteria.
Solution: The fungal cell wall is primarily composed of
chitin, a tough, nitrogen-containing homopolysaccharide.
Distractor Autopsy: - Cellulose & Lignin: Characteristic of plant cell walls.
- Murein: Characteristic of bacterial cell walls.
Cell without cell wall would burst in: (BUMHS-2022)
D
Solution having more electrolytes
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Osmosis dictates that water moves from an area of higher water potential (lower solute concentration) to lower water potential (higher solute concentration).
Solution: In a
hypotonic solution, the external environment has more free water than the cell interior. Water rushes in, causing an animal cell (or a plant cell stripped of its wall) to swell and undergo osmotic lysis (burst).
Distractor Autopsy: - Hypertonic: Water leaves the cell, causing it to shrink (plasmolysis).
- Isotonic: No net movement of water.
Plant cell wall is mainly made up of: (DUHS-2022)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The primary structural component of the plant kingdom's extracellular matrix is a specific carbohydrate polymer.
Solution: The primary plant cell wall is chiefly made up of
cellulose (a polymer of $\beta$-D-glucose), along with some pectin and hemicellulose.
Distractor Autopsy: - Lignin: Found only in secondary cell walls of woody tissues.
- Cutin: A waxy coating on the epidermis, not the main structural wall.
- Murein: Bacterial cell wall material.
Cell become dead due to the deposition of: (DUHS-2022)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Secondary thickening in plant cells often involves highly rigid, impermeable polymers that restrict nutrient flow, leading to programmed cell death.
Solution: Lignin is deposited in the secondary cell walls of specialized plant cells (like xylem vessels and sclerenchyma). It is highly impermeable and tough. Once fully lignified, the cell loses its protoplasm and becomes structurally dead, functioning only as a mechanical support or water pipe.
Distractor Autopsy: Cellulose and chitin allow for a living, metabolically active cell to exist within.
Movement of molecules against the concentration gradient is: (UHS-2022)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Moving molecules from a region of lower concentration to a region of higher concentration requires energy.
Solution: Active transport uses cellular energy (usually ATP) to pump molecules against their natural concentration gradient using specific membrane carrier proteins (pumps).
Distractor Autopsy: Passive transport and facilitated diffusion only allow molecules to move down their concentration gradients.
Why it is said that plasma membrane is asymmetrical? (NUMS-2022)
A
Proteins are not fixed at their position
B
Hydrophobic tail facing inward and hydrophilic head facing outward
C
The two surface and halves are not identical
D
Cholesterol molecules are only present inside
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The inner and outer leaflets of the plasma membrane have distinct compositions based on their differing cellular roles.
Solution: The membrane is asymmetrical because the two surfaces and halves are not identical. The outer leaflet contains glycoproteins and glycolipids (forming the glycocalyx) which are absent on the inner cytosolic leaflet. Furthermore, the specific types of phospholipids differ between the two halves.
Distractor Autopsy: Protein mobility (fluidity) and lipid bilayer orientation (hydrophobic inside) describe its fluid and barrier properties, not its asymmetry.
The ____ part of plasma membrane controls the fluidity of the membrane. (NUMS-2022)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Membrane fluidity is highly dependent on temperature and the chemical structure of its hydrophobic core.
Solution: The lipids (specifically, the ratio of saturated to unsaturated fatty acid tails in phospholipids, and the presence of cholesterol) primarily control the fluidity of the membrane. Unsaturated tails create kinks that prevent tight packing, keeping it fluid.
Distractor Autopsy: Proteins dictate membrane function (transport, signaling), while carbohydrates dictate cell recognition.
Which molecules do not contribute to the formation of biological membranes? (NUMS-2022)
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: Biological membranes are composed of a specific set of macromolecules.
Solution: Nucleoproteins are complexes of nucleic acids (DNA/RNA) and proteins (e.g., histones, ribosomes). They are located inside the nucleus or cytoplasm and play no role in forming the plasma membrane.
Distractor Autopsy: Phospholipids form the main matrix, while glycoproteins and glycolipids are crucial components of the cell membrane's outer surface.
A group of ribosomes attached to mRNA is known as polysome and the attachment is controlled by: (NUMS-2022)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Ribosomal subunits are typically separate in the cytoplasm and only associate to form an active ribosome during protein synthesis.
Solution: The association of the large and small ribosomal subunits to form a functional ribosome (and subsequently attach to mRNA as a polysome) is strictly dependent on the concentration of magnesium ions, \(\text{Mg}^{+2}\).
Distractor Autopsy: Sodium, Calcium, and Potassium ions are essential for cellular functions like nerve impulses, but are not the primary agents for ribosomal subunit binding.
Adenylate cyclase, in the cell membrane acts as: (SZABMU-2022)
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: Membrane proteins serve various functions, including enzymatic activity for intracellular signaling.
Solution: Adenylate cyclase is an integral membrane protein that acts as an enzyme. Upon activation by a G-protein, it catalyzes the conversion of ATP into cyclic AMP (cAMP), a crucial secondary messenger.
Distractor Autopsy: While it interacts with receptors, it is not a receptor itself, nor is it a transport channel or carrier.
The statement 'the membrane is like a sea of lipids in which proteins are floating' represents: (ETEA-2022)
A
Gortel and Grendel model
B
S. J. Singer and Nicholson model
C
J. F. Danielle and Davison model
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The historical progression of membrane models culminated in our modern understanding of membrane dynamics.
Solution: In 1972, S. J. Singer and G. L. Nicolson proposed the Fluid Mosaic Model. They beautifully described the membrane as a fluid "sea of lipids" in which mosaic "icebergs" of proteins float.
Distractor Autopsy: Danielli and Davson proposed the incorrect "sandwich model" where solid protein layers coated the outside of the lipid bilayer.
Facilitated diffusion involves carrier molecules. The carrier molecules are chemically ____ in nature. (BUMHS-2022)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Facilitated diffusion relies on specific structural components to ferry polar molecules across the hydrophobic membrane core.
Solution: The carrier molecules responsible for facilitated diffusion are chemically proteins (specifically, integral transport proteins). They undergo conformational changes to transport substances.
Distractor Autopsy: Lipids form the barrier, and carbohydrates act as identification tags. Neither can undergo the complex structural shifts required to transport molecules across the membrane.
Who proposed fluid mosaic model? (BUMHS-2022)
D
Robert Brown and Palade
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Recognizing key scientists is fundamental in biological history.
Solution: The fluid mosaic model, the universally accepted model for plasma membrane structure, was proposed by S. J. Singer and G. L. Nicolson in 1972.
Distractor Autopsy: Christian de Duve discovered lysosomes. Robert Brown discovered the nucleus. George Palade discovered ribosomes.
Plasma membrane is: (DUHS-2022)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: The cell must carefully regulate its internal environment to maintain homeostasis.
Solution: The plasma membrane is selectively permeable (or differentially permeable). It allows certain molecules (like small non-polar gases) to pass freely while restricting others (like large macromolecules and ions), selectively transporting them via proteins.
Distractor Autopsy: If it were completely permeable, the cell couldn't maintain homeostasis. If impermeable, the cell would die from starvation and waste buildup.
Which of the following are single membranous organelles? (UHS-2022)
A
Mitochondria and ribosomes
B
Golgi bodies, lysosome and ER
C
Cytosol, mitochondria and ribosomes
D
Golgi bodies, lysosome and mitochondria
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Organelles are classified by their membrane boundaries: non-membranous, single membrane, or double membrane.
Solution: The Endoplasmic Reticulum (ER), Golgi apparatus, and lysosomes form part of the endomembrane system and are all bounded by a
single membrane.
Distractor Autopsy: - Mitochondria & Chloroplasts: Double membrane bounded.
- Ribosomes: Non-membranous.
Glycogen, lipid droplets form the most important ____ of the cell. (SZABMU-2022)
B
Non-membranous organelles
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The cytoplasm contains both living machinery (organelles) and non-living stored materials.
Solution: Cell inclusions are non-living, temporary structures in the cytoplasm that consist of stored nutrients or secretory products, such as glycogen granules in liver cells or lipid droplets in adipocytes.
Distractor Autopsy: Organelles (membranous or non-membranous) possess metabolic activity, whereas inclusions are passive storage deposits.
Within the nucleus, ____ are made by the nucleolus. (NUMS-2022)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: The nucleolus is a dense, non-membranous region within the nucleus dedicated to RNA transcription and assembly.
Solution: The nucleolus acts as the factory for synthesizing ribosomal RNA (rRNA) and assembling it with imported proteins to form the large and small subunits of ribosomes.
Distractor Autopsy: Proteins and enzymes are synthesized in the cytoplasm by ribosomes. mRNA is transcribed in the nucleoplasm (outside the nucleolus).
The organelle which provides neurotransmitters in the nervous pathway is: (SZABMU-2022)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Secretory vesicles containing neurotransmitters must be meticulously packaged and sorted before reaching the synaptic terminal.
Solution: While the initial proteins are synthesized by the RER, it is the Golgi apparatus that modifies, packages, and buds off the final synaptic vesicles that provide neurotransmitters in the nervous pathway.
Distractor Autopsy: Glyoxysomes and Peroxisomes are involved in lipid metabolism and hydrogen peroxide breakdown, playing no role in neurotransmitter secretion.
What is true about smooth endoplasmic reticulum? (BUMHS-2022)
A
Involved in intracellular digestion
B
Involved in transmission of impulses
C
Involved in removal of storage and waste products
D
Involved in protein metabolism
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The SER has highly specialized functions in specific cell types, such as muscle cells.
Solution: In muscle cells, a specialized form of SER called the sarcoplasmic reticulum sequesters and releases Calcium ions (\(\text{Ca}^{+2}\)), which is an essential step in the transmission of impulses leading to muscle contraction.
Distractor Autopsy: Intracellular digestion is done by lysosomes. Protein metabolism is the RER's job.
Which organelles would be more abundant in a secretory cell than non-secretory cell? (NUMS-2022)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: The abundance of specific organelles in a cell is directly proportional to the cell's specialized physiological role.
Solution: Secretory cells (like glandular cells in the pancreas) produce and export large amounts of substances (enzymes, hormones). Therefore, they require an abundant Golgi complex, which acts as the central hub for modifying, sorting, and packaging these products into secretory vesicles.
Distractor Autopsy: Lysosomes handle intracellular digestion, vacuoles handle storage, and centrioles handle cell division. None of these are primarily responsible for exocytosis/secretion.
When and who discovered Golgi apparatus? (BUMHS-2022)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Historical milestones in cell biology are often tested as factual recall.
Solution: The Golgi apparatus was discovered by the Italian physician and biologist Camillo Golgi in the year 1898 while investigating the nervous system.
Distractor Autopsy: The dates 1888, 1988, and 1998 are historically inaccurate for this major discovery.
Which of the following cell does not possess Golgi apparatus? (BUMHS-2022)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The defining characteristic of prokaryotic cells is the absence of membrane-bound organelles.
Solution: A bacterial cell is a prokaryote. Prokaryotes strictly lack all membrane-bound organelles, including the Golgi apparatus, Endoplasmic Reticulum, and Mitochondria.
Distractor Autopsy: Animal, plant, and fungal cells are all eukaryotic and therefore possess a Golgi apparatus to handle their intracellular transport and secretion needs.
The digestive vacuoles and autophagosomes are also known as: (UHS-2022)
C
Primary lysosomes and autophagy
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: Lysosomes undergo structural and functional changes once they begin actively digesting material.
Solution: When a newly formed (primary) lysosome fuses with a food vacuole or an autophagosome, it becomes an active digestive compartment known as a secondary lysosome.
Distractor Autopsy: Phagocytosis is the process of eating, not the organelle. Primary lysosomes are inactive (pre-fusion). Peroxisomes belong to a completely different class of microbodies.
____ are spherical sacs surrounded by a single membrane and contain hydrolytic enzyme. (NUMS-2022)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Compartmentalization of destructive enzymes is crucial to prevent the cell from digesting itself.
Solution: Lysosomes are single-membrane-bound spherical sacs that contain a cocktail of powerful acid hydrolases (hydrolytic enzymes) used to digest macromolecules, old organelles, and engulfed pathogens.
Distractor Autopsy: Mitochondria and chloroplasts are double-membrane structures involved in energy conversion. Golgi bodies are stacks of flattened sacs (cisternae), not spherical sacs.
Intracellular digestion of food is done by the organelle: (SZABMU-2022)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Single-celled organisms and phagocytic cells rely on internal digestion mechanisms.
Solution: Once food is ingested via a food vacuole, a lysosome fuses with it. The lysosome's hydrolytic enzymes then break down the complex food molecules into simple nutrients.
Distractor Autopsy: While the food temporarily resides in a vacuole, the actual chemical digestion is performed by the enzymes provided exclusively by the lysosome.
The chloroplasts contain: (ETEA-2022)
A
Proteins, Ribosomes and small circular DNA
C
Small circular DNA only
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Chloroplasts are semi-autonomous organelles equipped to synthesize some of their own proteins.
Solution: In accordance with the endosymbiotic theory, chloroplasts contain all the necessary machinery for basic autonomy: small circular DNA, 70S ribosomes, and the resulting synthesized proteins.
Distractor Autopsy: Selecting "only" for any single component ignores the integrated biochemical system required for the chloroplast to function as a semi-autonomous unit.
Power house of the cell is: (DUHS-2022)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The cell requires a constant supply of energy in the form of ATP to survive.
Solution: The mitochondria are universally known as the powerhouses of the cell because they extract energy from organic fuels via aerobic respiration and convert it into ATP, the cell's energy currency.
Distractor Autopsy: Chloroplasts generate energy but specifically convert solar energy to chemical energy in plants. Ribosomes make proteins. ER makes lipids/proteins.
The structure which disappears during cell division is: (NUMS-2022)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: During mitosis, the nuclear architecture must be dismantled to allow spindle fibers to access the chromosomes.
Solution: As the cell enters prophase of cell division, the nuclear envelope disintegrates and the nucleolus completely disappears. This halts rRNA synthesis so the cell can focus all resources on division.
Distractor Autopsy: The Endoplasmic Reticulum also fragments, but in classical cytological context (and specific exam criteria), the "disappearance" of the nucleolus is the most prominent visual hallmark of prophase.
Except during nuclear division, nucleus has the chromosomes in loosely coiled state known as: (NUMS-2022)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: DNA packaging varies depending on the cell cycle phase to allow for either transcription (interphase) or transport (mitosis).
Solution: During interphase (non-dividing state), DNA is unwound and loosely coiled as a thread-like mass called chromatin, which allows enzymes to access genes for transcription and replication.
Distractor Autopsy: During division, chromatin condenses into distinct chromosomes. DNA is the molecule itself, and genes are segments of it. Ribosomes are outside the nucleus.
The colloidal mixture of ions, organic and inorganic salts present in the nucleus is called: (ETEA-2022)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: The nucleus contains its own distinct aqueous environment to support nucleic acid metabolism.
Solution: Nucleoplasm (or karyoplasm) is the highly viscous, colloidal liquid inside the nucleus that surrounds the chromatin and nucleolus. It contains a rich mixture of ions, nucleotides, and enzymes required for DNA/RNA synthesis.
Distractor Autopsy: The nuclear membrane is the boundary. The nucleolus is a dense structure. Chromosomes are the genetic material.
Structure formed by invagination of plasma membrane and involved in cell division and DNA replication of prokaryotic cell: (UHS-2022)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Without internal organelles, prokaryotes utilize inward folds of their plasma membrane to increase functional surface area.
Solution: Mesosomes are internal pouch-like invaginations of the bacterial plasma membrane. They hold respiratory enzymes and act as attachment points for the circular DNA, aiding in DNA replication and septation during binary fission.
Distractor Autopsy: Lysosomes and Golgi bodies are eukaryotic. Phragmoplasts are involved in eukaryotic plant cell wall formation.
Which one is common in both prokaryotic and eukaryotic cell? (UHS-2022)
C
Cytoplasmic streaming movement
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: All living cells must decode genetic information into proteins to survive.
Solution: Because protein synthesis is a universal requirement for life,
ribosomes (the non-membranous protein factories) are the essential structural components common to both prokaryotic and eukaryotic cells.
Distractor Autopsy: - Nuclear envelope & Cytoplasmic streaming (cyclosis): Strictly eukaryotic features.
- Binary fission: The primary mode of prokaryotic division (eukaryotes use mitosis).
In which type of cells, cell wall is not present? (PMC-2020)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Animal cells lack a rigid cell wall, utilizing only a flexible plasma membrane as their outermost boundary.
Solution: Liver cells are animal cells (hepatocytes). Therefore, they do not possess a cell wall. Their outermost boundary is the cell membrane.
Distractor Autopsy: Plant cells (cellulose), Fungal cells (chitin), and Bacterial cells (peptidoglycan) all inherently possess cell walls.
According to the fluid mosaic model of cell membrane, which zone is embedded inside? (PMC-2020)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Phospholipids are amphipathic molecules, meaning they have distinct water-loving and water-fearing regions.
Solution: In an aqueous environment, phospholipids organize into a bilayer where the non-polar, fatty acid tails point inward to escape water. Thus, the embedded inner zone of the membrane is strictly hydrophobic (water-repelling).
Distractor Autopsy: The hydrophilic (water-loving) phosphate heads face the outward and inward aqueous environments of the cell.
70S sized ribosomes are found in the cells of: (PMC-2020)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The evolutionary divergence between domains is reflected in ribosomal size.
Solution: Bacteria are prokaryotes, and their standard cytoplasmic ribosomes have a sedimentation coefficient of 70S.
Distractor Autopsy: Fungi, protozoa, and algae are all eukaryotic organisms. Their primary cytoplasmic ribosomes are 80S (though their mitochondria/chloroplasts contain 70S, the question refers to the primary cell type).
Select the one which is not a function of smooth endoplasmic reticulum: (PMC-2020)
B
Processing of glycoproteins
C
Transmission of impulses
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Post-translational modification of proteins generally happens sequentially downstream from the ER.
Solution: The processing of glycoproteins (adding carbohydrate chains to proteins) primarily takes place in the Golgi apparatus, not the SER.
Distractor Autopsy: The SER is involved in lipid metabolism, transport of materials (via transition vesicles), and transmission of impulses (e.g., calcium release in sarcoplasmic reticulum of muscle cells).
Which of the following organelles are involved in the synthesis of plant cell wall? (PMC-2020)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The cell wall is a complex extracellular matrix composed of cellulose, hemicellulose, and pectins, which require specialized secretory machinery for construction.
Solution: The
Golgi complex (specifically its plant equivalent, dictyosomes) is responsible for synthesizing non-cellulosic matrix polysaccharides (like pectins and hemicellulose) and packaging them into vesicles. These vesicles are then secreted to the plasma membrane to build the plant cell wall.
Distractor Autopsy: - Endoplasmic reticulum: Synthesizes proteins and lipids but does not directly secrete cell wall polysaccharides.
- Lysosomes/Peroxisomes: Involved in digestion and detoxification, not structural synthesis.
Passive processes for the movement of molecules across cell surface membrane are: (MDCAT-2019)
A
Osmosis and phagocytosis
B
Pinocytosis and facilitated diffusion
C
Facilitated diffusion and osmosis
D
Diffusion and exocytosis
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Passive transport requires no expenditure of metabolic energy (ATP) because molecules move down their concentration gradient.
Solution: Both osmosis (movement of water) and facilitated diffusion (movement of molecules via carrier proteins) operate without ATP, classifying them as passive processes.
Distractor Autopsy: Phagocytosis, pinocytosis, and exocytosis are forms of bulk transport that require significant ATP expenditure (Active processes).
The fluid mosaic model of cell membrane is: (AJK-2019)
A
Carbohydrate chains are attached with phospholipid bilayer
B
In which protein molecules are free to move about in a fluid bilayer of phospholipid molecules
C
Phospholipid bilayer is enclosed in protein layer
D
Protein layers having scattered phospholipids
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The currently accepted model of the cell membrane emphasizes dynamic movement rather than a static sandwich structure.
Solution: Proposed by Singer and Nicolson, the Fluid Mosaic Model states that the membrane is a fluid bilayer of phospholipids in which various protein molecules are embedded and are free to move laterally, much like icebergs in a sea.
Distractor Autopsy: Options suggesting a "protein layer enclosing lipids" describe the obsolete Davson-Danielli (sandwich) model.
Cell permeability and transport processes of cell membrane depend upon its ____ component. (NTS-2019)
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: The fundamental barrier to the movement of substances across a cell membrane is lipid in nature.
Solution: The phospholipid bilayer is the core component that regulates permeability. Its hydrophobic core strictly prevents the free passage of polar molecules and ions, making the membrane differentially permeable.
Distractor Autopsy: Carbohydrates act as recognition markers. Cellulose is not found in the cell membrane (it forms the plant cell wall).
When plant cell receives a signal for death, it commits suicide by rupturing: (NTS-2019)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Programmed cell death (apoptosis) and necrosis eventually lead to the destruction of the cell's integrity.
Solution: According to the specific biological principles referenced in standard curricula for this exam, irreversible damage to or targeted rupturing of the cell membrane results in the immediate death of the cell, as it loses its ability to maintain homeostasis.
Distractor Autopsy: While the tonoplast can rupture in certain types of plant programmed cell death (hypersensitive response), the ultimate functional destruction cited here is tied to the cell membrane.
Glycolysis is the common stage in both aerobic and anaerobic respiration and it occurs in ____ of the cell. (AJK-2019)
B
Inner membrane of mitochondria
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: Cellular respiration happens in distinct cellular compartments.
Solution: Glycolysis (the splitting of glucose into two molecules of pyruvate) requires enzymes that are dissolved freely in the cytosol. Therefore, it occurs in the cytoplasm.
Distractor Autopsy: The Krebs cycle occurs in the mitochondrial matrix, and the Electron Transport Chain occurs on the inner mitochondrial membrane.
The cytoplasmic organelle commonly found both in prokaryotes and eukaryotes is: (AJK-2019)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: While prokaryotes lack membrane-bound organelles, they still require the essential machinery for life, such as protein synthesis.
Solution: Ribosomes are non-membranous organelles responsible for protein synthesis. Because they are not bound by a membrane, they are universally present in both prokaryotic (70S) and eukaryotic (80S) cells.
Distractor Autopsy: Mitochondria are membrane-bound (absent in prokaryotes). A nucleoid is an irregular region containing DNA in prokaryotes, not an organelle found in eukaryotes.
Smooth endoplasmic reticulum is responsible for the metabolism of: (MDCAT-2019)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The structural difference between Rough ER (having ribosomes) and Smooth ER dictates their biochemical roles.
Solution: The Smooth Endoplasmic Reticulum (SER) lacks ribosomes, rendering it incapable of protein synthesis. Instead, it is highly active in the synthesis and metabolism of lipids (like steroid hormones) and detoxification processes.
Distractor Autopsy: Protein metabolism occurs in the Rough ER and cytoplasm. Nucleic acid metabolism occurs primarily in the nucleus.
Which of these is solely present in plant cell only? (AJK-2019)
B
Smooth endoplasmic reticulum
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Distinct structural differences separate plant and animal cell anatomies.
Solution: Out of the options provided, the large central vacuole is an anatomical feature unique to plant cells, essential for storing water, nutrients, and waste, as well as providing mechanical support via turgor pressure.
Distractor Autopsy: Peroxisomes, smooth endoplasmic reticulum, and the cytoskeleton are ubiquitous across both plant and animal eukaryotic cells.
The finger like infoldings which are formed by inner membrane of mitochondria are called: (MDCAT-2019)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Maximizing surface area is a common biological strategy to increase the efficiency of membrane-bound chemical reactions.
Solution: The inner mitochondrial membrane folds inward to form cristae. These finger-like infoldings vastly increase the surface area available for housing the electron transport chain and ATP synthase complexes.
Distractor Autopsy: The matrix is the fluid inside. Porins are channel proteins on the outer membrane. Ribosomes are the protein factories.
The structure present in a eukaryotic cell but absent in prokaryotic cells is: (MDCAT-2019)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The primary evolutionary division of life is based on the packaging of genetic material.
Solution: The term "eukaryote" literally means "true nucleus." Eukaryotic cells have their DNA enclosed within a membrane-bound nucleus, whereas prokaryotes ("before nucleus") have their DNA freely floating in a region called the nucleoid.
Distractor Autopsy: Both prokaryotes and eukaryotes possess DNA, a cell surface membrane, and ribosomes (though sizes differ: 70S vs 80S).
Ribosomes are made up of ____ and ____. (MDCAT-2018)
D
Proteins and carbohydrate
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Ribosomes are structurally ribonucleoprotein complexes.
Solution: Chemically, ribosomes are composed of approximately equal amounts of ribosomal RNA (rRNA) and specific ribosomal proteins.
Distractor Autopsy: Lipids and carbohydrates do not form the structure of ribosomes; they are primarily involved in membrane structure and energy storage.
The cisternae break up into vesicles from ____ and ____ of Golgi complex. (MDCAT-2018)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The Golgi apparatus has a distinct polarity, with a receiving end and a shipping end.
Solution: The Golgi has a forming face (cis, convex) where vesicles from the ER arrive and fuse. After processing, the secretory vesicles bud off and break away from the trans face, which is concave and known as the maturing face.
Distractor Autopsy: The forming face is convex (receives), while the maturing face is concave (dispatches). Therefore, combining "forming" with "concave" or "maturing" with "convex" is structurally inaccurate.
These structures are involved in the breakdown of old organelles: (MDCAT-2018)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Cellular homeostasis requires the recycling of damaged or obsolete cellular components (autophagy).
Solution: Lysosomes are membrane-bound vesicles containing powerful hydrolytic enzymes. They fuse with worn-out organelles to break them down into basic monomers, a process known as autophagy.
Distractor Autopsy: - Peroxisomes/Glyoxysomes: Involved in lipid metabolism and detoxification.
- Leucoplasts: Starch/lipid storage organelles in plants.
Which statement is correct about mitochondria and chloroplast? (MDCAT-2018)
A
Number of mitochondria and chloroplast are same in all cells
B
Chloroplast and mitochondria are single membrane structure
C
Chloroplast and mitochondria cannot live independently
D
70S ribosome is attached with the inner membrane of mitochondria and chloroplast
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: Mitochondria and chloroplasts are semi-autonomous organelles originating from ancient prokaryotic endosymbionts.
Solution: Both organelles retain their own circular DNA and
70S ribosomes located within their matrix/stroma, which allow them to synthesize some of their own structural proteins.
Distractor Autopsy:- Single membrane: Both are double-membrane structures.
- Same number: Organelle counts vary depending on cell energy demands.
#121 of 143
MDCAT-2018, PMC-2020
The membrane separating the vacuole from cytoplasm is called: (MDCAT-2018, PMC-2020)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The plant central vacuole is highly selective in transporting ions and water.
Solution: The specialized single membrane that bounds the central vacuole of a plant cell is specifically named the
tonoplast. It is vital for regulating the movement of ions around the cell and maintaining turgor.
Distractor Autopsy: - Cristae: Folds of the inner mitochondrial membrane.
- Cisternae: Flattened sacs of the ER or Golgi.
- Vacuolar membrane: While technically descriptive, "tonoplast" is the strict biological term required.
Which organelle is required for aerobic respiration? (NTS-2018)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Aerobic respiration requires specialized compartments to maintain the proton gradients necessary for ATP synthesis.
Solution: The mitochondrion is the "powerhouse of the cell." It houses the Krebs cycle in its matrix and the Electron Transport Chain on its inner membrane, making it the absolute requirement for aerobic cellular respiration.
Distractor Autopsy: Plastids perform photosynthesis (in plants). The ER synthesizes lipids and proteins. The nucleus stores genetic material.
Which features do animal cells share with plant cells? (NTS-2017)
A
Chloroplast (Present), Cytoplasm (Present), Nucleus (Present), Mitochondria (Present)
B
Chloroplast (Absent), Cytoplasm (Present), Nucleus (Present), Mitochondria (Present)
C
Chloroplast (Present), Cytoplasm (Absent), Nucleus (Present), Mitochondria (Absent)
D
Chloroplast (Absent), Cytoplasm (Absent), Nucleus (Absent), Mitochondria (Present)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: While plant and animal cells are both eukaryotic, they have distinct organelle compositions based on their metabolic needs.
Solution: Both animal and plant cells possess a true nucleus, cytoplasm, and mitochondria (for cellular respiration). However, animal cells strictly lack chloroplasts because they are heterotrophic.
Distractor Autopsy: Any option claiming the presence of chloroplasts in animal cells is incorrect. Likewise, any option suggesting animal cells lack cytoplasm or a nucleus is fundamentally wrong for standard eukaryotic cells.
Select the organelle which is only present in animal cells: (MDCAT-2017)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Cell division mechanisms vary slightly between plant and animal cells, reflected in their organelle composition.
Solution: Centrioles are cylindrical structures involved in spindle fiber formation during animal cell division. Higher plant cells lack centrioles and form a spindle apparatus without them.
Distractor Autopsy: - Microtubules: Make up the cytoskeleton in both cell types.
- Ribosomes & R.E.R: Essential for protein synthesis in all eukaryotes.
Which of the following structure is present in both plant and animal cells but is absent in prokaryotic cells? (MDCAT-2017)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Eukaryotic cells possess a complex cytoskeleton, whereas prokaryotic cells have a much simpler, differing structural framework.
Solution: Microtubules are protein filaments (tubulin) forming the cytoskeleton in all eukaryotes (plants and animals). Prokaryotes lack true tubulin-based microtubules.
Distractor Autopsy: - Centrioles: Absent in higher plants.
- Plastids: Absent in animal cells.
- Sieve tubes: Specialized plant structures (phloem), absent in animals and prokaryotes.
Taking in of solid particle by cell is called: (MDCAT-2017)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: Cells use specialized vesicular transport to engulf macromolecules or entire microorganisms.
Solution: Phagocytosis (cell eating) is the process by which a cell uses its plasma membrane to engulf a large, solid particle to form an internal compartment called a phagosome.
Distractor Autopsy: - Pinocytosis: Intake of fluids.
- Exocytosis: Expulsion of materials.
Self-eating ability of the cells by using lysosomes is called: (MDCAT-2017)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Cells must recycle old or damaged organelles to maintain cellular health.
Solution: Autophagy (literally "self-eating") is the regulatory mechanism where lysosomes fuse with worn-out organelles (like old mitochondria) to degrade and recycle their components.
Distractor Autopsy: Phagocytosis and Pinocytosis relate to taking in materials from the outside of the cell, not internal recycling.
#128 of 143
MDCAT-2017, MDCAT-2019
Ribosomes present in prokaryotes are: (MDCAT-2017, MDCAT-2019)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Ribosomes are classified by their sedimentation rate in a centrifuge, measured in Svedberg units (S).
Solution: Prokaryotic cells possess slightly smaller ribosomes that sediment at
70S (composed of 50S large and 30S small subunits).
Distractor Autopsy: - 80S: Found in the cytoplasm of eukaryotic cells.
- 50S & 30S: These are individual subunits, not the intact ribosome.
Group of ribosomes attached to mRNA is called: (MDCAT-2017)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: To maximize efficiency, multiple ribosomes translate a single mRNA molecule simultaneously.
Solution: A single mRNA string with multiple ribosomes attached like beads on a thread is called a polysome (or polyribosome). This allows for the rapid production of many identical polypeptide copies.
Distractor Autopsy: A polynucleotide is a chain of nucleic acids (like DNA). A polysaccharide is a carbohydrate chain.
Which of the following organelle consist of two subunits? (MDCAT-2017)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The physical structure of the protein-synthesizing machinery is highly distinct from membranous organelles.
Solution: The ribosome is a non-membranous organelle that uniquely consists of two distinct parts: a large subunit and a small subunit, which interlock around mRNA during translation.
Distractor Autopsy: Mitochondria, plastids, and Golgi bodies are continuous, membrane-bound structures, not composed of separate dissociable "subunits".
Nuclear membrane is continuous with: (MDCAT-2017)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: The nuclear envelope does not exist in isolation; it is directly connected to the cell's internal transport network.
Solution: The outer membrane of the nuclear envelope is physically continuous with the membrane of the rough Endoplasmic Reticulum, allowing the space between the nuclear membranes to connect directly to the lumen of the ER.
Distractor Autopsy: The Golgi body receives vesicles from the ER but is not physically continuous with it.
Functionally, mesosomes can be compared with: (MDCAT-2017)
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: Prokaryotic cells must perform energy-yielding reactions without membrane-bound organelles.
Solution: Mesosomes are invaginations of the bacterial plasma membrane that contain respiratory enzymes. Because they serve as the site of cellular respiration and ATP generation in bacteria, they are functionally analogous to the mitochondria of eukaryotic cells.
Distractor Autopsy: Polysomes/Ribosomes are for protein synthesis. Golgi bodies are for secretion.
Ribosomal RNA is synthesized in: (MDCAT-2017)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: The assembly of ribosomes requires a dedicated, concentrated region of DNA transcription within the nucleus.
Solution: The nucleolus is a darkly staining, non-membranous region within the nucleus where the genes encoding Ribosomal RNA (rRNA) are actively transcribed and where initial ribosomal subunit assembly occurs.
Distractor Autopsy: Nucleoplasm is the fluid of the nucleus but the specific site of rRNA synthesis is the nucleolus. Golgi and peroxisomes are cytoplasmic organelles.
DNA molecule in prokaryotes is: (MDCAT-2017)
A
Single, circular, double stranded molecule not bound by membrane
B
Linear, double stranded molecule
C
Double, circular molecule
D
Single, circular, double stranded and membrane bound
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Prokaryotic genomes are optimized for rapid replication and simplicity.
Solution: The main genomic DNA in prokaryotes (like bacteria) consists of a single, circular, double-stranded DNA molecule that resides in the nucleoid region, not bounded by any nuclear membrane.
Distractor Autopsy: Eukaryotic DNA is linear and membrane-bound. Prokaryotic DNA is circular, but emphatically lacks a membrane boundary.
Out of the given options, choose the one which shows the structures found only in plants? (MDCAT-2016)
A
Chloroplast, cell wall, mitochondria
B
Vacuole, chloroplast, ribosomes
C
Chloroplast, microtubules, peroxisomes
D
Chloroplast, cell wall, large vacuole
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: Plant cells possess specific structures adapted for their autotrophic lifestyle and structural support that animal cells lack.
Solution: - Animal cells lack a cell wall, chloroplasts, and a large central vacuole.
- Plant cells have a rigid cellulose cell wall for support, chloroplasts for photosynthesis, and a large central vacuole to maintain turgor pressure.
Distractor Autopsy: - Ribosomes and Mitochondria: Found in both plant and animal cells.
- Microtubules and Peroxisomes: Common to both eukaryotic cell types.
Presence of large central vacuole is the characteristic of: (MDCAT-2016)
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept: Mature plant cells must maintain turgor pressure to support the plant's upright structure.
Solution: A defining feature of a mature plant cell is a single, large central vacuole that occupies up to 90% of the cell volume, pushing the cytoplasm and organelles against the cell wall to maintain turgidity.
Distractor Autopsy: Fungi and protists possess vacuoles, but they are typically much smaller and more numerous. Prokaryotes lack membrane-bound vacuoles.
Fluid mosaic model of plasma membrane states that protein molecules float in a fluid like ____ layer. (MDCAT-2015)
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept: The biological membrane is not a static solid, but a dynamic, two-dimensional fluid.
Solution: The Fluid Mosaic Model describes the membrane as a fluid phospholipid bilayer in which integral and peripheral proteins are embedded and can float or move laterally.
Distractor Autopsy: Carbohydrates, glucose, and galactose are associated with the exterior surface (glycocalyx) but do not form the fluid layer itself.
Which one of the following cell structures is involved in the synthesis of lipids? (MDCAT-2015)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: The endomembrane system compartmentalizes cellular synthesis.
Solution: The Smooth Endoplasmic Reticulum (SER) contains unique enzymes embedded in its membrane that are explicitly responsible for synthesizing lipids, including oils, phospholipids, and steroids.
Distractor Autopsy: The Golgi complex modifies and packages proteins. Mitochondria produce ATP. Centrioles organize spindle fibers.
Which organelle is bounded by two membranes? (MDCAT-2015)
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept: Organelles are categorized by their protective boundaries (none, one, or two membranes).
Solution: The nucleus, chloroplasts, and mitochondria are uniquely bounded by a double membrane (an inner and an outer membrane).
Distractor Autopsy: Lysosomes are single-membrane bounded. Ribosomes and the nucleolus are completely non-membranous.
The intake of liquid materials across the cell membrane is: (MDCAT-2014)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Bulk transport across the membrane occurs via vesicle formation, categorized by the physical state of the ingested material.
Solution: Pinocytosis (cell drinking) is the specific form of endocytosis involving the ingestion of liquid materials or extracellular fluid by the budding of small vesicles from the cell membrane.
Distractor Autopsy: - Phagocytosis: Intake of large solid particles (cell eating).
- Endocytosis: A general term that includes both pinocytosis and phagocytosis. Pinocytosis is the more precise answer for liquids.
Which substance from the following is important for the mechanical stability of cell membranes, as without it membranes quickly break and cells burst open? The hydrophobic region of these molecules help to prevent ion or polar molecules from passing through the cell membrane? (KMDC-2014)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: The fundamental structural framework of all biological membranes is a lipid bilayer.
Solution: Phospholipids form a continuous bilayer. Their hydrophobic tails face inward, preventing the free passage of water-soluble ions and polar molecules. This bilayer provides the essential mechanical barrier and stability of the cell.
Distractor Autopsy: While cholesterol modulates fluidity and stability, the fundamental structure that prevents the cell from bursting open and acts as the primary barrier is the phospholipid bilayer itself.
#142 of 143
MDCAT-2014, 2019
Which cell organelle is responsible for cell secretion? (MDCAT-2014, 2019)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Exocytosis of cellular products requires a specialized packaging and shipping center.
Solution: The Golgi body (or Golgi complex) is the primary secretory organelle of the cell. It receives raw proteins/lipids from the ER, refines them, and encloses them in secretory vesicles that fuse with the plasma membrane for external secretion.
Distractor Autopsy: Ribosomes make the proteins, but do not secrete them. Mitochondria and chloroplasts are solely energy converters.
Peptidoglycan or murein is a special or distinctive feature of cell wall in: (MDCAT-2014)
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept: Cell wall composition is a major taxonomic identifier across the domains of life.
Solution: The cell wall of bacteria is uniquely constructed from peptidoglycan (also called murein), a complex polymer of sugars and amino acids that forms a massive, mesh-like sacculus around the cell.
Distractor Autopsy: Plants and most algae use cellulose. Fungi use chitin.