Collagen Structure and Properties

Steps:

• Recall collagen's structure: triple helix of three polypeptide chains.
• Identify statement 1: likely incorrect, as collagen is not a single chain but three intertwined.
• Verify statement 2: correct, collagen has high glycine and proline content for helix stability.
• Confirm statement 3: correct, collagen provides tensile strength in connective tissues.

Why D is correct:

• D selects 2 and 3 only, matching collagen's amino acid composition and structural role per biochemistry definitions.

Why the others are wrong:

• A includes 1, which misstates chain number.
• B includes 1 but excludes 3, omitting key function.
• C excludes 2, ignoring essential amino acids.

Not enough information on exact statements, but based on standard facts.

Final answer: D