A-LevelBiologyEnzymes9700/22 · Feb/Mar 2023 · Q65 Marks
Collagen is the most common structural protein in vertebrates. Collagen provides the skin with flexibility and strength.
- (a)Collagen is the most common structural protein in vertebrates. Collagen provides the skin with flexibility and strength. Explain how the structure of a collagen fibre provides the skin with strength.[3]
- (b)The enzyme collagenase breaks down collagen. Collagenase has several important medical uses, such as in the treatment of burnt skin. Scientists investigated the effect of pH on the activity of collagenase at 37°C. The results of their investigation are shown in Fig. 6.1. 100- 80- percentage 60- of maximum activity 40- 20- 0+ 4.0 5.0 6.0 7.0 8.0 9.0 10.0 pH Fig. 6.1 Explain why the activity of collagenase is lower at pH 8.0 than at the optimum pH.[2]
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Mark scheme
Marking points from the official mark scheme (Feb/Mar 2023). The mark or mark type is shown in brackets.
- [3] Question 6(a) Answer any three from: covalent bonds between collagen molecules (between R groups / side-chains); covalent bonds are strong; (molecules) staggered / overlapping molecules, so no weak areas (gives greater strength); (in skin) fibres line up in layers, not parallel / running in different directions ; provides tensile strength / strength in different directions ;
- [2] Question 6(b) Answer any two from: at pH 8.0: ionic / hydrogen bonds, (between R groups) broken / altered ; active site shape altered ; (active site) no longer / less, complementary to substrate / collagen or fewer enzyme-substrate complexes formed ; AVP; e.g. the amino acids in the active site affected by the changing pH ref. to partial denaturation
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