Biology Biomolecules UHS 2023
PMDC Verified Question 41 of 142
Biologically, ____ plays key roles in maintaining the integrity of lipid bilayer membranes.
A
Hydrophilic exclusion
B
Heat of vaporization
C
Hydrophobic exclusion
D
Specific heat capacity
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Hydrophobic exclusion
Concept:

Cell membranes are not held together by covalent bonds, but rather by the powerful physical forces exerted by surrounding water.

Solution:

  • Water molecules are highly polar and constantly seek to form low-energy hydrogen bonds with each other.


  • When non-polar (hydrophobic) fatty acid tails are placed in water, they disrupt these hydrogen bonds. Consequently, the water molecules aggressively "squeeze" the tails away to restore their own bonding network.


  • This phenomenon, Hydrophobic exclusion, forces the lipid tails into a tight, shielded bilayer core, completely defining and stabilizing the structural integrity of every cell membrane.


Why other options are incorrect:

  • Hydrophilic exclusion: A non-existent/incorrect term. Polar heads are hydrophilic and actively interact with water, they are not excluded.


  • Heat properties: Relate strictly to temperature control, not membrane aggregation.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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