Which bond is responsible for holding the alpha helix of a protein in shape?
Correct answer: B. hydrogen bonds between backbone carbonyl and amide groups
- A. peptide bonds along the backbone
- B. hydrogen bonds between backbone carbonyl and amide groups
- C. disulphide bridges between cysteines
- D. ionic bonds between side chains
Explanation
Regular hydrogen bonding between a carbonyl oxygen and an amide hydrogen four residues further along coils the chain into a helix. Peptide bonds create the chain itself rather than its coiling, and disulphide and ionic interactions belong to the tertiary level. Heat breaks the hydrogen bonds easily, which is why helices unwind on denaturation.
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About Classification of Proteins
Proteins are classified by composition as simple, conjugated and derived proteins, and by shape as fibrous or globular proteins. The topic relates these classes to examples such as albumin, keratin, collagen, haemoglobin and casein, while distinguishing structural proteins from proteins with transport, catalytic or regulatory roles.
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