Concept:The secondary structure of proteins (like the \( \alpha \)-helix or \( \beta \)-pleated sheet) is stabilized by specific non-covalent interactions along the polypeptide backbone.
Formula:$$ \text{>C=O} \cdots \text{H-N<} $$
Solution:- The given structure (\( \alpha \)-helix) maintains its coiled shape because of regular hydrogen bonds.
- These hydrogen bonds form between the carbonyl oxygen (\( \text{C=O} \)) of one amino acid residue and the amide hydrogen (\( \text{N-H} \)) of another residue four positions down the chain.
Why other options are incorrect:Disulfide bridges are covalent bonds that stabilize tertiary structure. Van der Waals forces contribute to tertiary packing, but H-bonds specifically define secondary structure. Unpaired electrons are irrelevant here.
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.