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CAIE A Level Biology 9700

Enzymes questions

Exam-style questions on Enzymes, ordered from foundation to challenge. Pick one, write your answer the way you would in the exam, and it comes back marked against the mark scheme, point by point.

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Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.

  1. Describe4 marksStandardA company uses a bioreactor containing lactase immobilised in alginate beads to produce lactose-free milk. Describe the advantages of using the immobilised enzyme in this bioreactor compared to using free lactase in…
  2. Describe4 marksStandardA student investigated the hydrolysis of starch by amylase. A starch solution was mixed with amylase and incubated at 37°C. At 30-second intervals, a sample was removed and added to iodine reagent. The absorbance of…
  3. Explain5 marksStandardSalivary amylase catalyses the hydrolysis of starch into maltose. It does not catalyse the hydrolysis of cellulose, even though both starch and cellulose are polysaccharides composed of glucose monomers. Explain why…
  4. Compare5 marksStandardTwo enzymes, A and B, catalyse the same reaction. Their relative activities were measured at different pH values using appropriate buffer solutions, as shown in the table below. pH Relative activity of Enzyme A…
  5. Describe5 marksStandardA student investigates the effect of substrate concentration on the rate of an enzyme-catalysed reaction. The enzyme is lactase and the substrate is lactose. The rate of product formation is measured at different…
  6. Outline4 marksStandardA student is investigating the effect of temperature on the rate of an enzyme-catalysed reaction. The student has samples of the enzymes catalase and amylase, along with their respective substrates (hydrogen peroxide…
  7. Outline5 marksStandardEnzymes can be classified as intracellular or extracellular based on where they act. (a) State what is meant by an intracellular enzyme and an extracellular enzyme. (b) Name one example of an intracellular enzyme and…
  8. Describe5 marksStandardDescribe how enzymes catalyse reactions. In your answer, you should refer to: the effect on activation energy the formation of an enzyme-substrate complex the lock-and-key and induced-fit hypotheses for enzyme…
  9. Compare4 marksStandardA student measures the activity of two enzymes, P and Q, which catalyse the same reaction. The Michaelis-Menten constant (Km) for enzyme P is 0.4 mmol dm−3 and for enzyme Q is 2.0 mmol dm−3. Compare the affinities of…
  10. Explain4 marksStandardA student investigated the effect of temperature on the rate of an enzyme-catalysed reaction. The enzyme was isolated from a mesophilic bacterium and the substrate concentration was kept in excess. The initial rate of…
  11. Explain4 marksStandardCellulase is an extracellular enzyme secreted by certain fungi. It catalyses the hydrolysis of cellulose to glucose. Two hypotheses used to describe enzyme action are the lock-and-key hypothesis and the induced-fit…
  12. Compare4 marksStandardThe table below shows the Michaelis-Menten constant (Km) values for two different enzymes, A and B, that both catalyse the same reaction. Enzyme Km (mM) A 0.2 B 2.5 Compare the affinities of enzyme A and enzyme B for…
  13. Describe4 marksStandardIn a biotechnology company, an enzyme that converts a substrate into a high-value product is immobilised in alginate beads and used in a continuous-flow bioreactor. Describe the advantages of immobilising this enzyme…
  14. Describe5 marksStandardA student investigated the effect of substrate concentration on the activity of the enzyme dipeptidase from the thermophilic bacterium Bacillus caldox. The enzyme catalyses the hydrolysis of a synthetic dipeptide, X…
  15. Explain4 marksStandardA researcher is investigating an enzyme that catalyses the hydrolysis of a specific disaccharide. The enzyme's active site appears to have a rigid, pre-formed shape that exactly matches the shape of its substrate…
  16. Explain4 marksStandardA student investigated the effect of temperature on the activity of the enzyme lipase, which is secreted by the fungus Aspergillus niger. The enzyme was mixed with a lipid substrate in a buffer solution at pH 7.0. The…
  17. Describe4 marksStandardA student investigates the effect of pH on the activity of amylase. Two buffers of pH 7 and pH 9 are each mixed with a starch solution and the same volume of amylase. At regular intervals, a sample is removed and…
  18. Explain5 marksStandardA student investigates the effect of two different inhibitors, X and Y, on the activity of the enzyme lactase. They measure the initial rate of reaction (in arbitrary units) at various substrate concentrations. The…
  19. Compare5 marksStandardAn enzyme, arginase, was studied in both free solution and immobilised in alginate beads. The activity (rate of product formation, arbitrary units) was measured at various pH values using appropriate buffer solutions…
  20. Outline4 marksStandardA student investigates the effect of pH on the activity of amylase. They set up a series of buffered solutions at different pH values and add a known concentration of amylase and starch. To measure the rate of…
  21. Explain5 marksStandardExplain why an enzyme usually catalyses only one specific reaction. In your answer, refer to the structure of the active site, the formation of the enzyme–substrate complex, and the lock-and-key and induced-fit models.
  22. Outline4 marksStandardA student wants to investigate the effect of pH on the rate of starch digestion by the enzyme amylase. Outline how a colorimeter could be used to measure the progress of this reaction.
  23. Explain5 marksStandardThe effect of two different reversible inhibitors, I1 and I2, on the activity of an enzyme was investigated. Initial rates of reaction were measured at various substrate concentrations in the absence of inhibitor and…
  24. Compare4 marksStandardA student measures the Michaelis-Menten constant (Km) of two enzymes, lactase and sucrase, for their respective substrates (lactose and sucrose) under identical conditions. The results are shown in the table below…
  25. Outline5 marksStandardA student examines two enzymes: amylase, which is secreted by salivary glands into the mouth, and catalase, which is found inside liver cells. (a) Outline the mode of action of enzymes, including the role of the active…
  26. Describe5 marksStandardA student investigates the effect of substrate concentration on the initial rate of an enzyme-catalysed reaction. The enzyme is maintained at its optimum temperature and pH. The initial rate is measured at various…
  27. Explain5 marksStandardAn enzyme-catalysed reaction was investigated at a range of substrate concentrations, both in the absence and in the presence of a reversible inhibitor. The initial rate of reaction (μmol product min⁻¹) was measured…
  28. Describe4 marksStandardA student investigated the action of amylase on starch. Amylase was added to a starch solution at 30 °C. At intervals, a sample was removed, iodine solution was added, and the absorbance was measured using a…
  29. Describe5 marksStandardThe enzyme urease catalyzes the hydrolysis of urea to ammonia and carbon dioxide. The activation energy for this reaction is lower in the presence of urease than without the enzyme. Describe how an enzyme such as…
  30. Explain5 marksStandardThe enzyme catalase is found in many cells and catalyses the decomposition of hydrogen peroxide into water and oxygen. Explain why catalase catalyses only the decomposition of hydrogen peroxide and no other reactions.
  31. Outline5 marksStandardLipase X is an enzyme produced by pancreatic cells and released into the small intestine, where it catalyses the breakdown of lipids into fatty acids and glycerol. (a) Outline whether lipase X is an intracellular or…
  32. Compare5 marksStandardA student investigates the effect of pH on the activity of an enzyme, using buffer solutions to maintain constant pH. The table below shows the relative activity of the enzyme at various pH values. pH Relative activity…
  33. Compare7 marksChallengeA student investigates the effect of pH on the activity of two different enzymes, A and B, using buffer solutions to maintain each pH. Table 1 shows the relative activity of each enzyme at various pH values. pH…
  34. Describe6 marksChallengeA biotechnology company produces a valuable chemical using an enzyme-catalysed reaction. The enzyme is inhibited by its own product, which accumulates and reduces the reaction rate. To overcome this, the enzyme is…
  35. Describe6 marksChallengeAn enzyme-catalysed reaction is studied at various substrate concentrations and the initial rate of product formation is measured. Describe the relationship between substrate concentration and initial rate. In your…
  36. Compare7 marksChallengeIn human liver cells, two different enzymes (Enzyme P and Enzyme Q) catalyse the same reaction: the phosphorylation of glucose to glucose-6-phosphate. Their Km values for glucose are shown in the table below. Enzyme Km…
  37. Describe6 marksChallengeA bacterial enzyme, hydrolase X, catalyses the breakdown of a pollutant substrate S. The initial rate of reaction was measured at different substrate concentrations. The results are shown in the table. [Substrate] / mM…
  38. Explain5 marksChallengeA student carries out an experiment to investigate the specificity of amylase. They add 1 cm³ of amylase solution to two test tubes: one containing 5 cm³ of starch solution and the other containing 5 cm³ of cellulose…
  39. Outline7 marksChallengeA student investigates two enzymes obtained from a mammal. Enzyme X is collected from saliva. The student mixes a sample of saliva with a 1% starch solution and uses a colorimeter to measure the rate of disappearance…
  40. Compare7 marksChallengeA student investigates the effect of pH on the activity of the enzyme xylanase from a soil bacterium. The enzyme is assayed either in free solution or immobilised in calcium alginate beads. Buffer solutions are used to…
  41. Describe6 marksChallengeA student investigated the effect of pH on the activity of salivary amylase using a colorimeter. Reaction mixtures containing starch, amylase, and iodine solution were set up at pH 5, 6, 7, and 8. The colorimeter…
  42. Explain5 marksChallengeA newly discovered enzyme, cellulase X, hydrolyses cellulose into glucose. It also shows weak hydrolytic activity on hemicellulose, a polysaccharide similar in structure to cellulose. The active site of cellulase X is…
  43. Outline7 marksChallengeAmylase is an extracellular enzyme that hydrolyses starch to maltose. A student wants to investigate the effect of temperature on the activity of amylase using a colorimeter. Outline the molecular basis of enzyme…
  44. Explain5 marksChallengeA researcher investigates the effect of an inhibitor X on the enzyme 'Formase', which catalyses the conversion of formate to carbon dioxide. The initial rate of reaction was measured at various substrate concentrations…
  45. Compare7 marksChallengeTwo enzymes, lactase (from E. coli) and cellulase (from Trichoderma reesei), catalyse the hydrolysis of different substrates. Their kinetic parameters are shown in the table. Enzyme Substrate Km (mM) Vmax (μmol min⁻¹…
  46. Explain5 marksChallengeAn enzyme from a thermophilic bacterium was immobilised in alginate beads to study its activity at different temperatures. The initial rate of reaction was measured at each temperature under conditions of saturating…
  47. Describe6 marksChallengeThe enzyme urease catalyses the hydrolysis of urea into ammonia and carbon dioxide. Describe the mechanism by which urease lowers the activation energy for this reaction. In your description, include the roles of the…
  48. Explain5 marksChallengeA student investigated the effect of temperature on the rate of a protease-catalysed reaction. The initial rate of reaction (in arbitrary units) was measured at different temperatures. The results are shown in the…
  49. Explain5 marksChallengeA researcher investigates a newly discovered enzyme, esterase E, which hydrolyses the ester bond in substrate X. The rate of hydrolysis is measured for substrate X and for a modified substrate Y, which differs from X…
  50. Explain5 marksChallengeAn enzyme (X) from yeast catalyses the conversion of substrate Y into product Z. The initial rate of reaction was measured at various substrate concentrations, both in the absence of any inhibitor and in the presence…
  51. Explain5 marksChallengeA novel enzyme, Xylanase-4, is found in a soil bacterium and catalyses the hydrolysis of xylan, a polysaccharide found in plant cell walls. The enzyme does not catalyse the hydrolysis of cellulose, starch, or other…
  52. Describe6 marksChallengeIn a metabolic pathway, an enzyme catalyses the conversion of substrate to product. The activation energy for the uncatalysed reaction is 120 kJ mol^-1, but in the presence of the enzyme it is reduced to 45 kJ mol^-1…
  53. Explain5 marksChallengeA newly discovered bacterium, Pseudomonas plasticivorans, secretes an extracellular enzyme called PETase. PETase is a globular protein that catalyses the hydrolysis of the synthetic polymer PET (polyethylene…
  54. Outline7 marksChallengeA student is investigating the effect of pH on the rate of hydrolysis of starch by the enzyme amylase. Starch does not absorb visible light strongly, but it forms a blue-black colour with iodine solution. The student…
  55. Describe6 marksChallengeA student investigates the hydrolysis of a disaccharide by the enzyme sucrase. In the absence of sucrase, the reaction requires an activation energy of 128 kJ mol⁻¹. When sucrase is added, the activation energy is…
  56. Explain5 marksChallengeA student investigated the effect of temperature on the rate of reaction of a protease enzyme. The enzyme was mixed with a casein substrate and the rate of product formation was measured at each temperature. The…
  57. Describe6 marksChallengeAn experiment was carried out to investigate the effect of pH on the rate of starch hydrolysis by amylase. Equal volumes of starch solution and amylase solution were mixed at pH 7 and pH 5. Samples were taken every 2…
  58. Outline7 marksChallengeA student investigates two enzymes. Enzyme X is obtained from the lysosomes of a rat liver cell. Enzyme Y is obtained from the secretion of a pancreatic cell. The student measures the rate of reaction of each enzyme at…