O-LevelBiologyEnzymes5090/21 · May/June 2016 · Q610 Marks
Enzyme Q is active in the human alimentary canal. Fig. 6.1 shows the effect of pH on the rate of reaction of enzyme Q. [Figure 6.1]
- (a)(i)Use the information in Fig. 6.1 to name the region of the alimentary canal where enzyme Q is active.[1]
- (a)(ii)Use your knowledge of the 'lock and key' hypothesis of enzyme action to explain why enzyme Q is active only in this region of the alimentary canal and not in any other region.[6]
- (b)All enzymes contain carbon. List three other chemical elements that must be present in each molecule of an enzyme. 1 2 3[3]
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Mark scheme
Marking points from the official mark scheme (May/June 2016). The mark or mark type is shown in brackets.
- [1] stomach ;
- [max 6] enzyme and substrate are lock and key;
- reference to optimum pH/(hydrochloric) acid (in stomach);
- active site;
- complementary AW ;
- substrate;
- if pH changes/alkaline ;
- enzyme denatured/changes shape AW;
- (substrate) no longer fits ;
- [3] hydrogen;
- oxygen;
- nitrogen ;
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