Mode of action of enzymes: past paper questions
Real questions on mode of action of enzymes
The newest 20 of 190 written questions. Open one to see it on the real paper.
- 9700/21 · October/November 2025 · Q3a[2]
The lock‑and‑key hypothesis and the induced‑fit hypothesis are used to describe the interaction of enzymes and their substrates. Describe one similarity and one difference between the lock‑and‑key hypothesis and the induced‑fit hypothesis. similarity difference
See it on the paper → - 9700/21 · October/November 2025 · Q3c[3]
Muscle cells contain glycogen phosphorylase. Fig. 3.3 shows the effect of caffeine on the activity of glycogen phosphorylase at different concentrations of substrate. 200 Key without caffeine with caffeine 150 glycogen phosphorylase 100 activity / arbitrary units 50 0 5 10 15 20 25 concentration of substrate / mmol dm...
See it on the paper → - 9700/22 · October/November 2025 · Q3e(i)[2]
Lactase supplements (tablets) can be taken before milk or milk‑based products are consumed to avoid symptoms of lactose intolerance. A student compared the activity of two different concentrations of a lactase supplement using an artificial substrate, ONPG, instead of lactose. A solution of ONPG is colourless, but the...
See it on the paper → - 9700/22 · October/November 2025 · Q3e(ii)[4]
The lactose in milk can be hydrolysed using immobilised lactase or using lactase free in solution (free lactase). This results in milk and milk products that do not contain lactose and so are suitable for lactose‑intolerant people. Scientists carried out an investigation to compare the activity of lactase immobilised i...
See it on the paper → - 9700/23 · October/November 2025 · Q3a[3]
Describe the induced-fit hypothesis of enzyme action.
See it on the paper → - 9700/23 · October/November 2025 · Q3b(i)[4]
With reference to the data in Fig. 3.2, discuss whether subtilisin A is effective in preventing the attachment of the larvae.
See it on the paper → - 9700/23 · October/November 2025 · Q3b(ii)[2]
The scientists extended their investigation by applying the polymer with immobilised subtilisin A to the outside of the bottom of small ships. Two factors that need to be taken into consideration in this type of investigation are the temperature and pH of the sea water. Outline two other factors that need to be taken i...
See it on the paper → - 9700/41 · October/November 2025 · Q7b[6]
Rotenone is a compound that affects oxidative phosphorylation. Suggest and explain how rotenone reduces the production of ATP and water in aerobic respiration. Rotenone disrupts the first carrier in the electron transport chain by stopping the transfer of electrons from this carrier.
See it on the paper → - 9700/41 · October/November 2025 · Q9a[2]
Fig. 9.1 shows a longitudinal section of a human kidney. X Y Fig. 9.1 X Name the regions of the kidney labelled X and Y in Fig. 9.1.
See it on the paper → - 9700/42 · October/November 2025 · Q6a[4]
Phosphoinositide 3‑kinase (PI3K) and protein kinase B (PKB) are enzymes involved in the regulation of blood glucose concentration. Fig. 6.1 shows a cell‑signalling pathway involving insulin, PI3K and PKB in a muscle cell. insulin glucose cell surface membrane receptor PI3K activation PKB cytoplasm GLUT4 transport prote...
See it on the paper → - 9700/42 · October/November 2025 · Q6b[7]
Describe how a biosensor can be used to measure blood glucose concentration.
See it on the paper → - 9700/42 · October/November 2025 · Q7b[3]
Action potentials are produced by the Venus fly trap during the closure of a leaf. Each action potential is also associated with a refractory period. This is similar to the action potential and refractory period observed in a mammalian neurone during nerve impulse transmission. Explain the role played by the refractory...
See it on the paper → - 9700/52 · October/November 2025 · Q2a[2]
Calculate the percentage decrease in transpiration rate from 0 to 400 µmol dm –3 of ABA for the mutant variety. Show your working. percentage decrease =
See it on the paper → - 9700/52 · October/November 2025 · Q2b[2]
With reference to Fig. 2.1, suggest conclusions that can be made about the effect of different concentrations of ABA on the transpiration rates of the mutant variety. State the evidence that supports your conclusions.
See it on the paper → - 9700/52 · October/November 2025 · Q2c[3]
The scientists used a mutant variety of thale cress that has stomata that do not respond to ABA. The scientists concluded that ABA reduces water loss in thale cress by ways other than stomatal closure. Suggest additional information that is required to increase the confidence in this conclusion.
See it on the paper → - 9700/21 · May/June 2025 · Q1b(iii)[1]
State the type of reaction catalysed by maltase. Question 2 starts on page 4.
See it on the paper → - 9700/21 · May/June 2025 · Q3a(i)[3]
With reference to Fig. 3.1, Fig. 3.2 and Fig. 3.3, describe and explain the similarities between the progress of the two reactions.
See it on the paper → - 9700/21 · May/June 2025 · Q3a(ii)[2]
Suggest two advantages of using a colorimeter to investigate the progress of reactions such as those shown in Fig. 3.1.
See it on the paper → - 9700/21 · May/June 2025 · Q3b(i)[2]
Calculate the Michaelis–Menten constant, K m , for the enzyme VpSP37 using the information in Fig. 3.4. Show your working. K m =
See it on the paper → - 9700/21 · May/June 2025 · Q3b(ii)[2]
The scientists discovered other enzymes that were suitable for the industrial process. These enzymes had higher K m values than VpSP37. Explain the advantage of using the enzyme VpSP37 in the industrial process rather than one of these other enzymes with higher K m values.
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What examiners said
Many gave an acceptable suggestion of how a protease can act on different substrates. Some used their knowledge of competitive inhibitors to suggest that the protein substrates had similar shapes so that they had a complementary shape to the active site of the protease. Others applied their understanding of induced fit to suggest that the enzyme active site could change shape to allow different su...
— Examiner report, October/November 2023, 9700/22 Q2(b) (Cambridge)
Table 2.1 was often correctly completed. The most frequent error was to inaccurately extract data from Fig. 2.1 and state the lower temperature of A22 as 37 °C. Some candidates did well in completing the table correctly and when completing the blank spaces below the table, they gave temperature and pH values rather than naming the keratinases involved.
— Examiner report, October/November 2023, 9700/22 Q2(d) (Cambridge)
Good answers used values accurately extracted from Fig. 2.1 and Fig. 2.2 to discuss advantages and disadvantages of the two keratinases as enzymes for washing detergents. Some candidates had noted the information that keratinases suitable for washing detergents should function well in alkaline conditions and decided to discuss only the results for pH, even though the question asked them to refer t...
— Examiner report, October/November 2023, 9700/22 Q2(e) (Cambridge)
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