Biology 9700 · AS & A Level · Protein synthesis

Protein synthesis — practice question

A collagen molecule is made from three identical polypeptides arranged in a triple helix. Glycine accounts for one third of the amino acids in a collagen molecule. Fig. 5.1A shows a polypeptide molecule while protein synthesis is in progress. A glycine molecule is shown immediately before it is added to the polypeptide.
(a(i))[2]

Complete Fig. 5.1B to show the glycine molecule attached to the end of the polypeptide.

(a(ii))[1]

State the type of reaction that takes place when glycine is added to the end of the polypeptide.

(a(iii))[2]

Explain the importance of glycine in a collagen molecule.

(b)[4]

Explain how the structure of collagen is linked to its functions in the mammalian body.

(c)[5]

Describe the mode of action of collagenase.

(d)[4]

With reference to Fig. 5.2, describe and explain the effect of pH on the activity of collagenase.

Worked solution & mark scheme

This 18-mark question has a full step-by-step worked solution and mark scheme. One marking point: Correct peptide bond shown with $H_2O$ removed

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