plumiEnzyme inhibitors: OCR A‑Level Biology A questions
OCR A-Level Biology A past-paper questions on 2.1.4.5 Enzyme inhibitors, 2016–2025, with mark schemes and examiner’s reports where available.
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Q17(a)(ii)
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All 21 questions on Enzyme inhibitors, as a list
- June 2025, Paper 1, Q17(a)(ii) (3 marks): The intermediate compound PEP is a reversible non-competitive inhibitor of PFK. Explain how PEP inhibits PFK. [3]
- June 2025, Paper 1, Q17(a)(iii) (2 marks): ATP is also an inhibitor of PFK. Suggest and explain why ATP cannot be a competitive inhibitor of PFK. [2]
- June 2025, Paper 1, Q17(a)(iv) (1 mark): Inhibition of PFK by ATP and PEP is an example of a negative feedback control mechanism. State the name of this type of inhibition in metabolic pathways such as
- June 2025, Paper 1, Q17(a)(v) (2 marks): ATP is converted to ADP and then AMP (adenosine monophosphate) when ATP provides energy for processes in the cell. AMP reverses the inhibition of PFK by ATP. Us
- June 2025, Paper 1, Q17(b) (1 mark): Complete the following sentence. Some inhibitors form strong covalent bonds with enzymes and are known as inhibitors. [1]
- June 2025, AS Paper 1, Q22(b)(ii) (2 marks): Drugs that affect DNA replication are used to treat cancer. Zelpolib is a drug that affects the enzyme DNA polymerase by binding to its active site. Suggest exp
- June 2024, AS Paper 1, Q25(b) (2 marks): Hydroxylamine inhibits catalase. Describe how the student could show that hydroxylamine is a competitive inhibitor. [2]
- June 2023, Paper 3, Q2(d)(ii) (2 marks): A scientist investigates the effect of vitamin C on the activity of the enzyme adenylyl cyclase. Adenylyl cyclase catalyses the conversion of ATP to cAMP. The s
- November 2021, Paper 1, Q5 (1 mark): The figure shows the metabolic pathways leading to synthesis of five amino acids: aspartate, lysine, methionine, threonine and isoleucine. E1 to E8 represent di
- November 2021, Paper 1, Q18(b) (3 marks): Liver is a rich source of the enzyme catalase. The table below describes examples of three terms from the list below. coenzyme competitive inhibition enzyme-pro
- November 2021, Paper 1, Q18(c) (1 mark): Fig. 18.2 shows the effect of concentration of hydrogen peroxide on the rate of reaction of catalase. rate of reaction of catalase (cm3 O2 min–1) concentration
- November 2021, AS Paper 2, Q4(a) (3 marks): Mosquito nets help to prevent the spread of malaria. They are often treated with an insecticide called permethrin. Some mosquitoes have developed resistance to
- November 2020, Paper 2, Q11 (1 mark): Which of the following, A to D, is true of a competitive enzyme inhibitor? A binds to a site other than the active site B changes the shape of the active site C
- June 2019, Paper 2, Q15 (1 mark): The image below shows a diagram of an enzyme. allosteric site active site Which of the following could be a competitive inhibitor of this enzyme? A B C D Your a
- June 2019, AS Paper 1, Q7 (1 mark): The diagram below shows the effect of changing substrate concentration on the rate of an enzyme- controlled reaction. rate of reaction substrate concentration W
- June 2018, Paper 1, Q5 (1 mark): The following graph shows the rate of reaction of an enzyme in different substrate concentrations. A B rate of C reaction D substrate concentration Which letter
- June 2018, AS Paper 2, Q4(b)(i) (2 marks): Describe how a non-competitive inhibitor works to inhibit the activity of an enzyme. [2]
- June 2018, AS Paper 2, Q4(b)(ii) (2 marks): Catalase is found in all living things that are exposed to oxygen. It protects cells from oxidative damage by breaking down hydrogen peroxide to water and oxyge
- June 2018, AS Paper 2, Q4(b)(iii) (2 marks): What can the students conclude from their results? [2]
- June 2018, AS Paper 2, Q4(b)(iv) (3 marks): Three rivers in the Himalayan foothills were polluted with copper, which affected the aquatic wildlife. Scientists were provided with one dead Indian Barb fish,
- June 2017, Paper 3, Q4(b)(i) (4 marks): What can you conclude from Fig. 4 about the molecules or ions that affect the functioning of the nitrogenase enzyme? [4]
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