S
4 Enzymes are biological catalysts. The diagram below shows how the enzyme, sucrase, breaks down a molecule of sucrose.
sucrose
sucrase
H2 O
glucose
fructose
a Describe how sucrase catalyses the breakdown of sucrose. You should refer to the diagram above in your answer.
b Three enzymes, P, Q and R, were extracted from different regions of the alimentary canal of a mammal. The effect of pH on the activity of the enzymes was investigated at 40 °C. The results are shown in the diagram below. P
Q
[3]
R
100 75 Rate of enzyme activity / arbitrary 50 units 25 0
0
1
2
3
4
5
6 pH
7
8
9
10
11
12
i Explain why the investigation was carried out at 40 °C. ii Using information in the diagram above, describe the effects of increasing pH on the rate of activity of enzyme Q. [Cambridge IGCSE• Biology 0610/33, Question 3, October/November 2010]
Original material © Cambridge University Press 2014
[2] [3]
Chapter 5: Enzymes
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