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Proteins and enzymes: OCR A‑Level Biology B questions

Every OCR A-Level Biology B exam question on 2.1.3 Proteins and enzymes, 2016–2025, with its mark scheme and examiner’s report.

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1,889 questions

  1. Q2(a)(i)

    June 2025 · Paper 2

    6 marks2.1.3 Proteins and enzymes
    The whole paper ↗
    June 2025 Paper 2, question 2(a)(i): (i)* Blood clotting is an essential process that protects against excessive bleeding when a blood vessel is damaged. Describe the mechanism of blood clotting an

  2. Q2(a)(ii)

    June 2025 · Paper 2

    2 marks2.1.3 Proteins and enzymes
    The whole paper ↗
    June 2025 Paper 2, question 2(a)(ii): Styptic pencils can be used to stop bleeding from minor cuts, such as cuts from shaving. A styptic pencil is a stick of hydrated salt, which acts as a vasoconst

  3. Q2(b)(i)

    June 2025 · Paper 2

    2 marks2.1.3 Proteins and enzymes
    The whole paper ↗
    June 2025 Paper 2, question 2(b)(i): Explain how analysis of LDH in a blood sample can be used to assess the severity of tissue damage. [2]

  4. Q2(b)(ii)

    June 2025 · Paper 2

    2 marks2.1.3 Proteins and enzymes
    The whole paper ↗
    June 2025 Paper 2, question 2(b)(ii): Screening for tissue damage uses gel electrophoresis to separate different forms of LDH. The table shows the five different forms of LDH and their main location

  5. Q5

    June 2025 · AS Paper 1

    1 mark2.1.3 Proteins and enzymes
    The whole paper ↗
    June 2025 AS Paper 1, question 5: The graph shows the rate of an enzyme-controlled reaction with and without the addition of a fixed quantity of substance Z. Without substance Z Rate of With sub

  6. Q4(a)(i)

    June 2025 · AS Paper 2

    1 mark2.1.3 Proteins and enzymes
    No published mark scheme
    The whole paper ↗
    June 2025 AS Paper 2, question 4(a)(i): Explain why the students waited 10 minutes to add the photographic film to the test tube. [1]

  7. Q4(a)(ii)

    June 2025 · AS Paper 2

    2 marks2.1.3 Proteins and enzymes
    No published mark scheme
    The whole paper ↗
    June 2025 AS Paper 2, question 4(a)(ii): Give two reasons why the students’ results may not be valid. 1 2 [2]

  8. Q4(b)

    June 2025 · AS Paper 2

    1 mark2.1.3 Proteins and enzymes
    No published mark scheme
    The whole paper ↗
    June 2025 AS Paper 2, question 4(b): Explain why trypsin can digest the gelatin protein in the photographic X-ray film but cannot digest other protease molecules. [1]

  9. Q4(c)(i)

    June 2025 · AS Paper 2

    2 marks2.1.3 Proteins and enzymes
    No published mark scheme
    The whole paper ↗
    June 2025 AS Paper 2, question 4(c)(i): Explain how the students calculated the relative rate of enzyme activity in this investigation. [2]

  10. Q4(c)(ii)

    June 2025 · AS Paper 2

    2 marks2.1.3 Proteins and enzymes
    No published mark scheme
    The whole paper ↗
    June 2025 AS Paper 2, question 4(c)(ii): State two conclusions that can be made from the data in the graph. [2]

  11. Q4(c)(iii)

    June 2025 · AS Paper 2

    2 marks2.1.3 Proteins and enzymes
    No published mark scheme
    The whole paper ↗
    June 2025 AS Paper 2, question 4(c)(iii): State two explanations for the differences in the results for trypsin activity at 35 °C and 50 °C. [2]

  12. Q4(d)

    June 2025 · AS Paper 2

    6 marks2.1.3 Proteins and enzymes
    No published mark scheme
    The whole paper ↗
    June 2025 AS Paper 2, question 4(d): (d)* Gelatin is produced from the breakdown of collagen, a structural protein found in bones and cartilage. The image below shows part of a molecule of collagen

  13. Q4

    June 2024 · Paper 1

    1 mark2.1.3 Proteins and enzymes
    The whole paper ↗
    June 2024 Paper 1, question 4: Which of the statements about the blood clotting process is not correct? A Fibrinogen fibres form a mesh to trap red blood cells. B Platelets are activated and

  14. Q36(b)(ii)

    June 2024 · Paper 1

    3 marks2.1.3 Proteins and enzymes
    The whole paper ↗
    June 2024 Paper 1, question 36(b)(ii): Explain the mechanism of inhibition by which saquinavir affects the activity of HIV protease enzymes. [3]

  15. Q5

    June 2024 · AS Paper 1

    1 mark2.1.3 Proteins and enzymes
    The whole paper ↗
    June 2024 AS Paper 1, question 5: The tertiary structure of a protein molecule is shown below. B A CH2-S—S-CH2 C CH3 CH3 CH2-OH...O-C-CH2 - CH CH D CH3 CH3 OH + O–-C-CH2 CH2-NH3 O Which of the o

  16. Q2(a)

    June 2024 · AS Paper 2

    2 marks2.1.3 Proteins and enzymes
    The whole paper ↗
    June 2024 AS Paper 2, question 2(a): One of the chemical groups in valine has been labelled on the diagram. Circle and label two other chemical groups in valine on the diagram. [2]

  17. Q13

    June 2023 · Paper 1

    1 mark2.1.3 Proteins and enzymes
    The whole paper ↗
    June 2023 Paper 1, question 13: Heparin is a drug used to prevent blood clots. It binds to the enzyme that converts fibrinogen to fibrin during the blood clotting process. The diagram shows he

  18. Q9

    June 2022 · Paper 1

    1 mark2.1.3 Proteins and enzymes
    The whole paper ↗
    June 2022 Paper 1, question 9: Chelating agents are chemical compounds that target and react with metal ions in the body allowing them to be excreted. A chelating agent has been shown to redu

  19. Q31(c)(i)

    June 2022 · Paper 1

    1 mark2.1.3 Proteins and enzymes
    The whole paper ↗
    June 2022 Paper 1, question 31(c)(i): Using the information in Fig. 31.2, suggest a type of biological molecule found in the hydrophilic core of daptomycin. [1]

  20. Q35(b)

    June 2022 · Paper 1

    4 marks2.1.3 Proteins and enzymes
    The whole paper ↗
    June 2022 Paper 1, question 35(b): When blood vessels are damaged a clot is formed to prevent excessive blood loss. Complete the sentences about blood clotting using the most appropriate word or
All 84 questions on Proteins and enzymes, as a list
  1. June 2025, Paper 2, Q2(a)(i) (6 marks): (i)* Blood clotting is an essential process that protects against excessive bleeding when a blood vessel is damaged. Describe the mechanism of blood clotting an
  2. June 2025, Paper 2, Q2(a)(ii) (2 marks): Styptic pencils can be used to stop bleeding from minor cuts, such as cuts from shaving. A styptic pencil is a stick of hydrated salt, which acts as a vasoconst
  3. June 2025, Paper 2, Q2(b)(i) (2 marks): Explain how analysis of LDH in a blood sample can be used to assess the severity of tissue damage. [2]
  4. June 2025, Paper 2, Q2(b)(ii) (2 marks): Screening for tissue damage uses gel electrophoresis to separate different forms of LDH. The table shows the five different forms of LDH and their main location
  5. June 2025, AS Paper 1, Q5 (1 mark): The graph shows the rate of an enzyme-controlled reaction with and without the addition of a fixed quantity of substance Z. Without substance Z Rate of With sub
  6. June 2025, AS Paper 2, Q4(a)(i) (1 mark): Explain why the students waited 10 minutes to add the photographic film to the test tube. [1]
  7. June 2025, AS Paper 2, Q4(a)(ii) (2 marks): Give two reasons why the students’ results may not be valid. 1 2 [2]
  8. June 2025, AS Paper 2, Q4(b) (1 mark): Explain why trypsin can digest the gelatin protein in the photographic X-ray film but cannot digest other protease molecules. [1]
  9. June 2025, AS Paper 2, Q4(c)(i) (2 marks): Explain how the students calculated the relative rate of enzyme activity in this investigation. [2]
  10. June 2025, AS Paper 2, Q4(c)(ii) (2 marks): State two conclusions that can be made from the data in the graph. [2]
  11. June 2025, AS Paper 2, Q4(c)(iii) (2 marks): State two explanations for the differences in the results for trypsin activity at 35 °C and 50 °C. [2]
  12. June 2025, AS Paper 2, Q4(d) (6 marks): (d)* Gelatin is produced from the breakdown of collagen, a structural protein found in bones and cartilage. The image below shows part of a molecule of collagen
  13. June 2024, Paper 1, Q4 (1 mark): Which of the statements about the blood clotting process is not correct? A Fibrinogen fibres form a mesh to trap red blood cells. B Platelets are activated and
  14. June 2024, Paper 1, Q36(b)(ii) (3 marks): Explain the mechanism of inhibition by which saquinavir affects the activity of HIV protease enzymes. [3]
  15. June 2024, AS Paper 1, Q5 (1 mark): The tertiary structure of a protein molecule is shown below. B A CH2-S—S-CH2 C CH3 CH3 CH2-OH...O-C-CH2 - CH CH D CH3 CH3 OH + O–-C-CH2 CH2-NH3 O Which of the o
  16. June 2024, AS Paper 2, Q2(a) (2 marks): One of the chemical groups in valine has been labelled on the diagram. Circle and label two other chemical groups in valine on the diagram. [2]
  17. June 2023, Paper 1, Q13 (1 mark): Heparin is a drug used to prevent blood clots. It binds to the enzyme that converts fibrinogen to fibrin during the blood clotting process. The diagram shows he
  18. June 2022, Paper 1, Q9 (1 mark): Chelating agents are chemical compounds that target and react with metal ions in the body allowing them to be excreted. A chelating agent has been shown to redu
  19. June 2022, Paper 1, Q31(c)(i) (1 mark): Using the information in Fig. 31.2, suggest a type of biological molecule found in the hydrophilic core of daptomycin. [1]
  20. June 2022, Paper 1, Q35(b) (4 marks): When blood vessels are damaged a clot is formed to prevent excessive blood loss. Complete the sentences about blood clotting using the most appropriate word or
  21. June 2022, Paper 1, Q35(c)(i) (2 marks): Suggest one advantage and one disadvantage of using plasma to replace blood lost during childbirth. Advantage Disadvantage [2]
  22. June 2022, Paper 1, Q35(c)(ii) (1 mark): Apart from replacing lost blood, state one other use for donated plasma. [1]
  23. June 2022, Paper 3, Q3(a)(iii) (1 mark): Photosynthetic pigments have colours that make them visible on a chromatogram. Amino acids that are separated on a chromatogram are not visible. State the name
  24. June 2022, AS Paper 1, Q16 (1 mark): Which of the reactions is catalysed by the enzyme thromboplastin? A Fibrinogen fibrin B Fibrin fibrinogen C Prothrombin thrombin D Thrombin prothrombin Your ans
  25. June 2022, AS Paper 1, Q17 (1 mark): The relative amounts of the lactic acid dehydrogenase (LDH) isoenzymes in four different mouse tissues were measured using gel electrophoresis. Results for thre
  26. June 2022, AS Paper 1, Q25(d) (3 marks): Different products can be made from donated blood and then stored. Complete the sentences about stored blood products using the most appropriate word or words.
  27. November 2021, Paper 1, Q5 (1 mark): The diagram shows a blood bag label with information about the stored blood product contained in the bag. O INSTRUCTIONS Always check patient/component compatib
  28. November 2021, Paper 1, Q6 (1 mark): The table shows the results from an analysis of some of the organic compounds found in a human urine sample. Concentration (g dm–3) Carbon Nitrogen Oxygen Hydro
  29. November 2021, Paper 1, Q35(d)(i) (1 mark): Suggest how avidin prevents insects from obtaining biotin. [1]
  30. November 2021, Paper 1, Q35(d)(ii) (2 marks): Suggest why lack of biotin leads to the death of wheat weevils. [2]
  31. November 2021, Paper 2, Q4(a)(i) (3 marks): Describe how you could obtain the data for this graph. [3]
  32. November 2021, Paper 2, Q4(a)(ii) (1 mark): Explain why the experiments you have described should be carried out with excess enzyme. [1]
  33. November 2021, Paper 2, Q4(a)(iii) (2 marks): The Michaelis constant, KM, is defined as the substrate concentration that gives half the maximum reaction rate (1 2 Vmax). Use Fig. 4.1 to obtain a value for K
  34. November 2021, Paper 2, Q4(a)(iv) (2 marks): Suggest why it is often difficult to determine a value for Vmax experimentally. [2]
  35. November 2021, Paper 2, Q4(b)(i) (1 mark): Use Fig. 4.2 to determine the gradient of the line. Gradient = [1]
  36. November 2021, Paper 2, Q4(b)(ii) (1 mark): Write an expression that connects the gradient of the line, KM and Vmax. [1]
  37. November 2021, Paper 2, Q4(b)(iii) (2 marks): A student used Fig. 4.2 to determine that Vmax = 5. Use this value and your answer to part (i) to determine KM for this enzyme. KM = (units not required) [2]
  38. November 2021, AS Paper 1, Q16 (1 mark): After donation, blood is processed into different products. The table shows a description of some blood products and possible uses. Which of the rows, A to D, i
  39. November 2021, AS Paper 2, Q3(a)(i) (1 mark): State the independent and dependent variables in this investigation. Independent variable Dependent variable [1]
  40. November 2021, AS Paper 2, Q3(a)(ii) (2 marks): The temperature of the water in the beaker was maintained at 30 °C. Explain why the temperature had to be controlled. [2]
  41. November 2021, AS Paper 2, Q3(a)(iii) (1 mark): Temperature was maintained by adding hot water to the beaker. Give one method of maintaining temperature that is more accurate than adding hot water. [1]
  42. November 2021, AS Paper 2, Q3(b) (4 marks): State two variables, other than temperature, that should have been controlled in the investigation and explain why they could alter the results if they were not
  43. November 2021, AS Paper 2, Q3(c) (3 marks): Protein shakes containing casein are regularly used by athletes as a protein supplement. Fig. 3.2 shows the percentage of casein hydrolysed in the body followin
  44. November 2021, AS Paper 2, Q3(d) (2 marks): Soybean Trypsin Inhibitor, a naturally occurring inhibitor of trypsin, is found in soybeans. Suggest why animals fed on a diet of soybeans may have reduced musc
  45. November 2020, Paper 1, Q4 (1 mark): Which of the following, A to D, describes the structure of haemoglobin? A each of the four polypeptide chains is combined with an identical haem group B each po
  46. November 2020, AS Paper 1, Q19 (1 mark): The diagram shows an enzyme with its substrate before and after the attachment of molecule Q. substrate active site enzyme Q Which of the options, A to D, is mo
  47. November 2020, AS Paper 1, Q25(a) (5 marks): Using your knowledge, complete the passage about the enzyme catalase using the most appropriate term(s). Catalase is spherical, meaning it is a protein. It has
  48. November 2020, AS Paper 1, Q25(b)(i) (1 mark): Name the reaction involved and the bond that is broken during this process. reaction bond [1]
  49. November 2020, AS Paper 1, Q25(b)(ii) (2 marks): Part of the amino acid valine is shown below. C CH H3C CH3 R group Complete the diagram by drawing the full structure of the amino acid, valine. [2]
  50. June 2019, Paper 1, Q26 (1 mark): Trisodium citrate is a compound used for the long-term preservation of whole blood. The compound prevents blood clotting by reacting with an ion. Which of the o
  51. June 2019, Paper 2, Q2(a)(i) (1 mark): Draw a circle around the part of the structure that represents the peptide bond. [The response to this question should be drawn on the diagram.] [1]
  52. June 2019, Paper 2, Q2(a)(ii) (1 mark): Name the chemical reaction that joins the amino acids together in a peptide. [1]
  53. June 2019, Paper 2, Q2(b)(i) (2 marks): Suggest the importance of the following steps in the paper chromatography procedure. 1. The sample of α–defensin was heated with hydrochloric acid. 2. Care was
  54. June 2019, Paper 2, Q2(b)(ii) (2 marks): Fig. 2 shows the results of one analysis. A origin solvent front Fig. 2 Table 2 shows Rf values for six different amino acids. Amino acid Rf Arginine 0.16 Cyste
  55. June 2019, Paper 2, Q3(a) (3 marks): For each of the following features of MMP structure, draw a line connecting the feature to the correct description. Feature Description Primary structure The ac
  56. June 2019, Paper 2, Q3(c) (2 marks): Marimastat is an MMP inhibitor that was used in clinical trials as a potential treatment for cancer. Suggest how marimastat could inhibit MMPs to reduce the hyd
  57. June 2019, AS Paper 1, Q6 (1 mark): Lactase is an enzyme found in mammals that breaks down lactose. Which of the molecules, A to D, would be found in a solution following the complete hydrolysis o
  58. June 2019, AS Paper 1, Q7 (1 mark): The diagram below is a chromatogram of three different amino acids. The distance travelled by the solvent from the baseline is 50 mm. solvent front 14 mm 36 mm
  59. June 2019, AS Paper 1, Q8 (1 mark): Haemoglobin is a protein molecule found in mammalian erythrocytes. Which of the statements, A to D, about the structure of haemoglobin is correct? A Primary str
  60. June 2019, AS Paper 1, Q23(a)(i) (3 marks): Using your knowledge of the role of thrombin in the blood-clotting process, explain how variegin acts as a competitive inhibitor. [3]
  61. June 2019, AS Paper 1, Q23(a)(ii) (1 mark): Fig. 23 shows the effect of two different inhibitors, Y and Z, on the activity of thrombin as substrate concentration increases. Curve X shows the effect of sub
  62. June 2019, AS Paper 1, Q23(a)(iii) (2 marks): Using Fig. 23, calculate the percentage decrease in rate of enzyme activity when inhibitor Z is present at a substrate concentration of 4.0 arbitrary units. Giv
  63. June 2019, AS Paper 1, Q23(b) (2 marks): Heparin is a blood-clotting inhibitor which can be used to treat people with a disorder known as antiphospholipid antibody syndrome (APS). People with APS produ
  64. June 2018, Paper 1, Q1 (1 mark): Which of the rows, A to D, from the table below indicates the type of bond present (3) or absent (8) in the secondary structure of a protein? Disulfide Hydrogen
  65. June 2018, Paper 1, Q36(b)(iii) (2 marks): The table below shows the results of the investigation. Diameter of clear zone (mm) Bacterial Standard species Plate 1 Plate 2 Plate 3 Mean deviation A 23 22 22
  66. June 2018, Paper 1, Q36(b)(iv) (2 marks): The investigation did not include any control experiment. Suggest one control experiment that could have been included in this investigation and explain its imp
  67. June 2018, Paper 1, Q36(b)(v) (1 mark): Suggest one other way in which the method could be changed to improve the validity of the conclusions. [1]
  68. June 2018, Paper 2, Q3(d) (4 marks): Studies have shown that HIV might increase the probability of clots forming inside blood vessels. A student wrote the following notes about the process of blood
  69. June 2018, AS Paper 1, Q14 (1 mark): The table shows the type of bond present in the different levels of structure for a protein molecule. Which of the rows, A to D, is correct? Primary structure S
  70. June 2018, AS Paper 1, Q20 (1 mark): Donated blood is processed into different products which can be used to treat patients with specific conditions. Which of the patients, A to D, would be treated
  71. June 2018, AS Paper 1, Q22(a)(i) (3 marks): Explain how the maximum rate of the reaction can still be achieved despite the presence of methotrexate. [3]
  72. June 2018, AS Paper 1, Q22(b) (1 mark): Aspirin is another example of an enzyme inhibitor that can be used for medical purposes. Aspirin acts as an anti-prostaglandin so is commonly used to treat infl
  73. June 2018, AS Paper 2, Q3(a)(ii) (2 marks): Quinine interferes with the ability of P. falciparum to completely digest haemoglobin resulting in the death of the parasite. Suggest how incomplete digestion o
  74. June 2017, Paper 1, Q7 (1 mark): The graph below shows the effect of alanine on the rate of a reaction catalyzed by the enzyme, pyruvate kinase. without alanine with alanine rate of reaction su
  75. June 2017, Paper 1, Q22 (1 mark): The diagram below represents an amino acid within a polypeptide sequence. Three regions of the amino acid are labelled 1 to 3. H R N C C 3 O H 1 2 Which of the
  76. June 2017, Paper 1, Q26 (1 mark): Fibrin is involved in the blood clotting cascade. Which of the options, A to D, identifies the factors required for the conversion of fibrinogen to fibrin? phos
  77. June 2017, Paper 1, Q37(c)(i) (1 mark): State which type of stored blood product would be required for a blood transfusion to treat severe anaemia. [1]
  78. June 2017, Paper 1, Q37(c)(ii) (2 marks): Identify the blood group of the patient tested in Fig. 37.2 and state which donor blood group(s) can be safely transfused to this patient. blood group of patien
  79. June 2017, Paper 2, Q1(b)(i) (1 mark): Explain why the units of carboxylase activity are ‘mol CO2 fixed per mol active sites s–1’ rather than just ‘mol CO2 fixed s–1’. [1]
  80. June 2017, AS Paper 1, Q6 (1 mark): The blood clotting process is a series of enzyme-controlled reactions. Which of the reactions, A to D, occurs in the blood clotting process? A Fibrinogen is con
  81. June 2017, AS Paper 1, Q10 (1 mark): The table below shows features of the blood types of four patients, 1, 2, 3 and 4. Antigens on Antibodies in blood erythrocytes plasma Patient 1 A and B none Pa
  82. June 2016, AS Paper 2, Q2(b) (1 mark): The students added a protease enzyme to the sports drink to produce a solution containing amino acids. Name the type of reaction catalysed by the protease enzym
  83. June 2016, AS Paper 2, Q2(c)(i) (3 marks): Using Fig. 2, which of the amino acids named in Table 2 could be X? Show working to support your answer. X = [3]
  84. June 2016, AS Paper 2, Q2(c)(ii) (2 marks): The students were concerned that they may not be able to distinguish between the amino acids phenylalanine and tryptophan on their chromatogram. Using the infor

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