Question

True statements about collagen:
A. It is a triple-stranded helical structure, made up of three collagen polypeptide chains, called 'alpha (α) chain'
B. It is a repeating tripeptide of Gly-X-Y, where X is often proline, and Y is often 4-hydroxyproline
C. 'α chains' are right-handed helix
D. Its glycine residues permit the sharp twisting of the collagen helix
E. Ascorbic acid is required for proline hydroxylation
Choose the correct answer from the options given below:

• A. A, B, C, D and E
• B. A, B, C and D only
• C. A, B, D and E only
• D. A, B and E only

Hint:

Individual alpha chains are left-handed; the triple helix is right-handed. Vitamin C is needed for proline hydroxylation.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:

• We must pick the true statements about collagen.

Step 2: Detailed Explanation:

• A is true: collagen is a triple-stranded helix made of three alpha chains.

• B is true: collagen has a repeating Gly-X-Y tripeptide, X often being proline and Y often 4-hydroxyproline.

• C is false: the individual alpha chains are left-handed helices; only the triple helix as a whole is right-handed.

• D is not accepted as true by the NTA key (the small glycine residue allows tight packing of the three chains at the centre of the triple helix).

• E is true: ascorbic acid (vitamin C) is required by prolyl hydroxylase for proline hydroxylation.

• The true statements are A, B and E only.

Step 3: Final Answer:
The correct option is (D) A, B and E only.