Biology Biomolecules MDCAT 2018
PMDC Verified Question 128 of 142
Which of the following holds the alpha helix of protein in its place?
A
Hydrogen bond
B
R-group
C
Disulphide bond
D
Amino group
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Hydrogen bond
Concept:

The structural stability of secondary shapes relies on extensive, repeating weak interactions.

Solution:

  • The α-helix is a right-handed coil where the backbone spirals around a central axis.


  • This delicate geometric spiral is held tightly in place entirely by Hydrogen bonds.


  • These bonds occur specifically between the slightly positive Hydrogen of an amino group (N-H) and the slightly negative Oxygen of a carboxyl group (C=O) located exactly four amino acids further down the chain.


Why other options are incorrect:

  • Disulphide bonds / R-group interactions: These strictly dictate the overall Tertiary (3D) folding pattern, not the local secondary helix.

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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