Essential Biology 03.6, AHL7.6 & SLC2: Enzymes
1.
What is an enzyme?
2. Which suffix is usually attached to the name of an enzyme?
3. Define active site.
4. An enzyme is which type of protein at which level of protein structure?
5. What are substrates and products?
6. What is the significance of polar amino acids with regard to the active site of an enzyme?
7. Use a diagram to explain the lock-and-key hypothesis of enzyme activity in terms of enzymesubstrate specificity.
8. Using further diagrams, explain why the induced fit model of enzyme activity is more
appropriate.
Stephen Taylor
Bandung International School
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Essential Biology 03.6, AHL7.6 & SLC2: Enzymes
9. What is activation energy?
10. How do enzymes lower the activation energy of a reaction?
11. Why is using an enzyme safer than using heat to speed biological reactions?
12. What is a metabolic pathway?
13. Give two cyclical examples of metabolic pathways.
14. Outline the process of blood clotting as an example of a metabolic pathway, beginning with
platelet/ cell damage.
Stephen Taylor
Bandung International School
http://sciencevideos.wordpress.com
Essential Biology 03.6, AHL7.6 & SLC2: Enzymes
15. What is denaturation?
16. In the space below, produce sketch-graphs to show the effects of temperature, pH and
substrate concentration on enzyme activity. Explain each graph.
17. Explain how enzymes are used in the production of lactose-free milk.
18. Briefly outline two other industrial uses of enzymes.
Stephen Taylor
Bandung International School
http://sciencevideos.wordpress.com
Essential Biology 03.6, AHL7.6 & SLC2: Enzymes
19. What is an inhibitor?
20. Using diagrams, explain the difference between competitive and non-competitive methods of
inhibition.
21. Outline the therapeutic use of one competitive inhibitor.
22. Outline the therapeutic use of one non-competitive inhibitor.
23. Explain the role of end-product inhibition as a method of controlling metabolic pathways.
Include the role of allosteric sites and give one example.
Stephen Taylor
Bandung International School
http://sciencevideos.wordpress.com
Essential Biology 03.6, AHL7.6 & SLC2: Enzymes
24. Alcohol dehydrogenase is an enzyme that catalyses the reversible reaction of ethanol and
ethanal according to the equation below.
CH3CHO + NADH + H+
ethanal
NAD + CH3CH2OH
ethanol
The initial rate of reaction can be measured according to the time taken for NADH to be
produced.
In an experiment, the initial rate at different concentrations of ethanol was recorded (no
inhibition). The experiment was then repeated with the addition of 1mmol dm-3
2,2,2-trifluoroethanol, a competitive inhibitor of the enzyme. A third experiment using a
greater concentration of the same inhibitor (3 mmol dm-3) was performed. The results for
each experiment are shown in the graph below.
1.2
1.1
1.0
0.9
0.8
0.7
Initial rate of reaction 0.6
0.5
/ arbitrary units
0.4
0.3
0.2
0.1
0.0
no inhibition
1 mmol dm–3 inhibitor
3 mmol dm–3 inhibitor
0
10
20
30
40
50
60
70
80
90
100
Ethanol concentration / mmol dm –3
From IB Biology past papers
(a)
[Source: R Taber, Biochemical Education, (1998) 26, pages 239-242]
Outline the effect of increasing the substrate concentration on the control reaction
(no inhibition).
(2)
(b)
(i)
State the initial rate of reaction at an ethanol concentration of 50 mmol dm–3
in the presence of the inhibitor at the following concentrations.
1 mmol dm–3:
3 mmol dm–3:
Stephen Taylor
Bandung International School
(1)
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Essential Biology 03.6, AHL7.6 & SLC2: Enzymes
(ii)
State the effect of increasing the concentration of inhibitor on the initial rate
of reaction.
(1)
(c)
Explain how a competitive inhibitor works.
(3)
(Total 7 marks)
25. The graph below shows the effect of changing the substrate concentration on an enzyme
controlled reaction.
40 % substrate
20 % substrate
10 % substrate
Amount of product formed
5 % substrate
2.5 % substrate
0 % substrate
Time
(Past paper question)
What is the correct interpretation of these data?
A.
The rate of reaction increases continuously with increase in substrate concentration.
B.
The rate of reaction decreases continuously with increase in substrate concentration.
C.
The rate of reaction increases up to a point and then remains constant.
D.
The rate of reaction is not affected by any change in the substrate concentration.
(1)
Stephen Taylor
Bandung International School
http://sciencevideos.wordpress.com