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ASBiologyCIEExam Questions3. Enzymes3.2 Factors that Affect Enzyme Action

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First exams 2025

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Factors that Affect Enzyme Action (CIE AS Biology)

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3.2 Factors that Affect Enzyme Action

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3.2 Factors that Affect Enzyme Action

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11 mark

Which statements would be true regarding the action of all enzyme inhibitors?

1

bind to the active site of an enzyme  

2

cause a change in the tertiary structure of an enzyme

3

reduce the rate of an enzyme catalysed reaction

  • 1, 2 and 3

  • 1 and 2 only

  • 2 and 3 only

  • 3 only

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21 mark

Hyperthermophiles grow optimally at temperatures between 80 and 110°C and comprise of species from both the bacterial and archaeal domains.  These organisms have been isolated from all types of terrestrial and marine hot environments, including natural and man-made environments. 

Which graph would represent the relationship between temperature and the rate of enzyme activity in hyperthermophiles?

screenshot-2023-05-07-105747

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    31 mark

    How does increasing substrate concentration affect the rate of an enzyme-catalysed reaction in the presence of a competitive inhibitor?

    • The rate of the reaction slows.

    • The rate of the reaction increases.

    • The rate of the reaction slows initially and then recovers.

    • The rate of the reaction is not affected by additional substrate.

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    41 mark

    Inhibitors of enzyme reactions form enzyme / inhibitor complexes.

    Which statements about enzyme inhibition are correct?

    1

    The initial rate of reaction is decreased.

    2

    The active site changes shape while forming the enzyme/inhibitor complex.

    3

    The inhibition can be competitive or non-competitive.

    4

    The maximum rate of reaction (Vmax) is increased. 

    • 1 and 3 only

    • 2 and 3 only

    • 1, 2 and 3 only

    • 2, 3 and 4 only

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    51 mark

    Pepsin is a digestive enzyme present in the stomach of humans. The stomach environment has a pH of 2.5.  Pepsin is most active in acidic environments between pH 1.5 to 2.5. The optimum temperature of pepsin is between 37°C and 42°C. 

    Which of the following statements is not true?

    • Raising the pH of the stomach will decrease pepsin activity.

    • Above 42°C the bonds in pepsin begin to break.

    • Above pH 2.5 the tertiary structure of pepsin is changed.

    • Temperatures below 37°C result in more enzyme/substrate complex being formed.

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    61 mark

    Which properties are characteristic of a competitive inhibitor of an enzyme?

      binds effect of adding more substrate
    A at active site reduces inhibition
    B at active site does not reduce inhibition
    C at allosteric site reduces inhibition
    D at allosteric site does not reduce inhibition

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      71 mark

      The Vmax is the rate of reaction when the enzyme is saturated with substrate. This graph shows the effect of increasing substrate on enzyme activity.  

      screenshot-2023-05-08-104123

      What mass of substrate is equal to the ½ Vmax?

      • 50g

      • 150g

      • 250g

      • 350g

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      81 mark

      Enzymes can be immobilised in various ways. The diagram below shows two different ways of immobilisation 

      screenshot-2023-05-08-104557

      Immobilised lactase enzymes can be used to make milk digestible for lactose intolerant people.  Which of the following statements about the milk produced by the use of immobilised lactase enzymes is not correct?

      • The milk would contain glucose and galactose monosaccharides

      • The milk would taste sweeter and be easier to digest

      • The milk would contain lactase enzymes

      • The milk would look the same as regular milk

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      91 mark

      The graph shows the effect of substrate concentration on the rate of an enzyme-controlled reaction. The enzyme concentration is constant.diagram-4

      Which statement about the graph is correct?

      • Between X and Z the temperature is limiting

      • Between X and Z, the number of enzyme molecules is limiting

      • Between X and Y, the number of substrate molecules is limiting

      • Between Y and Z, the number of substrate molecules is limiting

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      101 mark

      The graph below shows the effect of pH on the rate on three different enzyme-controlled reactions. The enzyme concentration is constant.

      screenshot-2023-05-08-105407

      Which statement about the graph is not true?

      • At its optimum pH, enzyme Y has the fastest rate.

      • There is no pH at which both Y and Z have a functional active site.

      • There is no pH at which both X and Z have a functional active site.

      • There is no pH at which both X and Y have a functional active site.

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      11 mark

      The graph shows the rate of glucose production with increasing concentration of maltase.

      screenshot-2023-05-08-112513

       

      To get a graph with a linear correlation like this which procedure would not be necessary?

      • ensure temperature remained constant

      • ensure there is sufficient maltose availability

      • ensure pH remained constant

      • ensure there is sufficient glucose availability

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      21 mark

      This diagram shows a metabolic pathway.

      reactant rightwards arrow with enzyme space straight x on top intermediate space 1 space space rightwards arrow with enzyme space straight y on top space intermediate space 2 space space space rightwards arrow with enzyme space straight z on top end space product

      What would be the effect of adding a competitive inhibitor of enzyme z?

      • intermediate 2 would increase in concentration

      • enzyme z would be denatured

      • no more end product would be made

      • rate of reaction of enzyme x would slow

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      31 mark

      This graph shows the effect of temperature on enzyme activity 

      screenshot-2023-05-08-113140

      Which statement is not true? 

      • At W the kinetic energy of the substrate is highest 

      • At R the enzyme is completely denatured

      • At W the rate of enzyme/substrate formation is the highest

      • At E bonds in the enzyme have started to break

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      41 mark

      This graph shows the effect of increasing substrate on enzyme activity

      screenshot-2023-05-08-113354

      What is the Km value?

      • 50g

      • 250g

      • 350g

      • 500g

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      51 mark

      Enzymes can be immobilised in various ways. The diagram below shows two different ways of immobilisation 

      screenshot-2023-05-08-113954

      Immobilised lactase enzymes are used to make milk digestible for lactose intolerant people.  A student carried out an investigation to compare the activity of the enzyme lactase that had been immobilised in the two different ways shown.  

      A solution containing 50 mg cm–3 of lactose was poured through a column containing the immobilised enzyme.  The solution containing the products was collected and the concentration of glucose measured.

      What is the independent variable for this experiment? 

      • The amount of lactose in the solution before pouring through the column.

      • The amount of glucose in the milk after pouring through the column.

      • The type of enzyme immobilization.

      • The temperature of the solution.

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      61 mark

      In the graph, Z represents the rate of an enzyme reaction under optimal conditions and without an inhibitor.

      screenshot-2023-05-08-114345

      Which curve would represent the same experiment carried out in the presence of a low concentration of competitive inhibitor?

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        71 mark

        The graph shows the effect of enzyme concentration on the rate of an enzyme-controlled reaction. The substrate concentration is constant.

        screenshot-2023-05-08-114923

        Which statement about the graph is correct?

        • Between X and Z the number of enzyme molecules is limiting

        • Between Y and Z, the number of enzyme molecules is limiting

        • Between X and Z, the number of substrate molecules is limiting

        • Between Y and Z, the number of substrate molecules is limiting

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        81 mark

        The graph shows the effect of pH on the rate on three different enzyme-controlled reactions. The enzyme concentration is constant.

        screenshot-2023-05-08-115544

        Which statement about the graph is correct?

        • At its optimum pH, enzyme Z has the fastest rate

        • There is no pH in which both X and Y have a functional active site

        • Enzyme X has a functional active site across the widest range of pH’s

        • Enzyme Y has a functional active site across the narrowest range of pH’s

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        91 mark

        The graph shows the course of an enzyme-catalysed reaction at 25 °C.

        screenshot-2023-05-08-115957

        Which statement about the graph is incorrect?

        • At X the number of available substrate molecules is high

        • At X the number of enzyme/substrate complexes is the same as Y

        • At Z the number of available substrate molecules is low

        • At Y the number of enzyme/substrate complexes is the same as Z

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        101 mark

        The graph shows the course of two enzyme-catalysed reaction at 30 °C.  The only thing that was changed between experiment 1 and 2 was some additional substrate was added at the beginning of experiment 2

        screenshot-2023-05-08-120225

        Which statement about the experiment is not true?

        • At X the number of enzyme/substrate complexes is the same in both 1 and 2

        • At X the limiting factor in both experiment 1 and 2 is enzyme availability

        • At Z there are still enzyme/substrate complexes forming in experiment 2

        • At Y there are no more enzyme/substrate complex forming in experiment 1

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        11 mark

        The graphs show the rate of reaction of an enzyme-catalyzed reaction.

        Which graph shows the effect of increasing the concentration of the substrate both with and without a competitive inhibitor?

        screenshot-2023-05-08-120848

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          21 mark

          Question 22 - CIE IAS 3.2 Factors that Affect Enzyme Action - HARD

          This diagram shows a metabolic pathway occurring in an organelle.  The speed of this metabolic pathway is self-regulating as the end product acts as a competitive inhibitor to enzyme 2

          reactant space rightwards arrow with enzyme space 1 on top intermediate space straight X rightwards arrow with enzyme space 2 on top space intermediate space straight Y rightwards arrow with enzyme space 3 on top space end space product

          What would you not expect to occur when adding additional end product to the organelle?

          • enzyme 2 activity would decrease

          • amount of intermediate Y would decrease

          • amount of reactant would increase

          • amount of intermediate X would increase

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          31 mark

          Ethylene glycol is a colourless and odourless type of alcohol found in many household products.  People sometimes drink ethylene glycol mistakenly (or on purpose as a substitute for ethanol), however drinking it can cause profound shock, organ failure, and even death.  

          Ethylene glycol itself is not toxic, rather the products it gets broken down into.  The same enzyme in the body that normally breaks down ethanol into harmless products is also responsible for the hydrolysis of ethylene glycol.  This is due to ethylene glycol having a similar structure to ethanol.  Accordingly, the treatment for someone who has ingested ethylene glycol is a large dose of ethanol.  

          Which statement explains why this unusual treatment works?

          • Ethanol binds near the active site on the enzyme and alters its shape

          • Ethanol denatures the enzyme

          • Ethanol is more likely to bind to the active site of the enzyme

          • Ethanol acts as a pain killer 

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          41 mark

          Km is the concentration of substrate which permits the enzyme to achieve half Vmax.  An enzyme with a high Km requires a greater concentration of substrate to achieve Vmax.

          screenshot-2023-05-08-121908

          Which of the following statements is correct?

          • Enzyme 1 has the lower Km and therefore a greater affinity to its substrate

          • Enzyme 1 has the higher Km and therefore a greater affinity to its substrate.

          • Enzyme 2 has the lower Km and therefore a greater affinity to its substrate.

          • Enzyme 2 has the higher Km and therefore a greater affinity to its substrate.

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          51 mark

          The curve Z shows the activity of catalase at 25 °C. Curves A, B, C and D show the effect of different conditions on the activity of catalase.

          screenshot-2023-05-08-122307

          Which curve shows the effect of increasing the temperature by 10 °C and adding additional substrate?

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            61 mark

            Enzymes can be immobilized in various ways. The diagram below shows two different ways of immobilization:

            screenshot-2023-05-08-122600

            Immobilised lactase enzymes are used to make milk digestible for lactose intolerant people.  A student carried out an investigation to compare the activity of the enzyme lactase that had been immobilised in the two different ways shown.  

            A 500 cm3 solution containing 50 mg cm–3 of lactose was poured through a column containing the immobilised enzyme.  The solution containing the products was collected and the concentration of glucose measured.

            The student collected the following data:

              method of immobilisation
            A B
            time for solution to pass through column / seconds 36 28
            glucose concentration of end solution / mg cm–3 20 14


            What was the rate of glucose production in method             A in mg cm–3 min-1 rounded to two significant figures?

            • 33

            • 33.33

            • 0.55

            • 0.56

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            71 mark

            In the graph, Z represents the relationship between the initial rate of reaction of an enzyme and the concentration of its substrate under optimal conditions and without an inhibitor.

            screenshot-2023-05-08-123813

             

            Which curve would represent the same experiment carried out in the presence of a low concentration of a non-competitive inhibitor?

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              81 mark

              The graph shows the effect of substrate concentration on the rate of an enzyme-controlled reaction. The enzyme concentration is constant.

              screenshot-2023-05-08-124115

              Which statement about the graph is correct?

                Between X and Y Between Y and Z
              A Enzyme is limiting rate Enzyme is limiting rate
              B Enzyme is limiting rate Substrate is limiting rate
              C Substrate is limiting rate Enzyme is limiting rate
              D Substrate is limiting rate Substrate is limiting rate

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                91 mark

                Km is the concentration of substrate which permits the enzyme to achieve half Vmax.

                screenshot-2023-05-08-124653

                Which of the following statements is incorrect?

                • Enzyme 2 has a greater affinity for its substrate than enzyme 1

                • Enzyme 1 reaches its Vmax

                • The Km value of enzyme 2 is greater than the Km value of enzyme 1

                • The Vmax value of enzyme 2 is greater than the Vmax value of enzyme 1

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                101 mark

                Immobilised lactase enzymes are used to make milk digestible for lactose intolerant people.  A student carried out an investigation to compare the activity of the enzyme lactase that had been immobilised in the two different ways shown below:

                screenshot-2023-05-08-125057

                 

                A 500 cm3 solution containing 50 mg cm–3 of lactose was poured through a column containing the immobilised enzyme.  The solution containing the products was collected and the concentration of glucose measured:

                  method of immobilisation
                A B
                time for solution to pass through column / seconds 36 28
                glucose concentration of end solution / mg cm–3 2.0 1.4
                rate of glucose production / mg sec-1 0.055 0.05

                Assuming the mass of glucose is equal to half the initial lactose concentration (i.e. 1 mg of glucose indicates the hydrolysis of 2 mg of lactose), how much lactose could be hydrolysed by method B in an hour with unlimited starting solution?

                • 180 mg

                • 360 mg

                • 1.4 mg

                • 2.8 mg

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