Biology 9700 · AS & A Level
Factors that affect enzyme action
100 practice questions on Factors that affect enzyme action, with worked solutions and instant marking.
The speed of enzyme-catalysed reactions in human cells is controlled. What might be involved in this control?
Feb/March 2016
The graphs illustrate how temperature and pH affect enzyme activity. Which statement correctly explains the enzyme activity?
Feb/March 2016
Which of the following is not an example of antibiotic action?
Feb/March 2016
The table shows data gathered by a student during an investigation into how temperature affects an enzyme-catalysed reaction. All other variables were kept constant. What is the correct conclusion?
Feb/March 2017
What measurement could be used to calculate the rate of an enzyme-catalysed reaction?
Feb/March 2018
The graph illustrates how substrate concentration affects the initial rate of an enzyme-catalysed reaction. The enzyme concentration remains constant. Which statement about the graph is accurate?
Feb/March 2019
Rifampicin is an antibiotic that is used to treat tuberculosis (TB). It acts by blocking RNA polymerase in bacteria. Which processes are directly blocked by this antibiotic?
Feb/March 2019
A heating sleeve was fitted around the trunk of a small tree at a height of $1\,\text{m}$ above the ground. This made it possible to warm a narrow section of the trunk to $60\,^{\circ}\text{C}$. How would heating this section to $60\,^{\circ}\text{C}$ affect the movement of phloem sap and xylem sap between the roots and leaves?
Feb/March 2019
Catechol is a chemical present in several fruits. The enzyme catechol oxidase can oxidise catechol into a quinone. Catechol oxidase is inhibited by parahydroxybenzoic acid (PHBA), which has a structure similar to catechol. When PHBA is present, the Michaelis-Menten constant ($K_m$) of catechol oxidase increases. In what way does PHBA inhibit catechol oxidase?
Feb/March 2021
Which relationships could be studied by means of a colorimeter?
Feb/March 2022
A scientist studied how two enzyme-catalysed reactions progressed in separate test-tubes, X and Y. Each reaction produced colour changes that could be detected by colorimetry. $0.5\,\text{cm}^3$ samples were removed from each test-tube at the beginning of the investigation and then at regular intervals over the following 5 minutes. Copper ions were introduced into each sample immediately after collection so that the enzymes were inactivated and the reactions could not continue. The absorbance of every sample was determined with a colorimeter. The graph presents the findings from this investigation. Which statement is consistent with the results shown in the graph?
Feb/March 2024
An enzyme is fully denatured at $50\,^{\circ}\text{C}$. A fixed concentration of this enzyme is added to a fixed concentration of its substrate. The time needed to complete the reaction is measured at different temperatures. Which graph shows the results?
May/June 2010
An enzyme becomes fully denatured at $50\,^{\circ}\text{C}$. A constant concentration of this enzyme is mixed with a constant concentration of its substrate. The time for the reaction to reach completion is recorded at different temperatures. Which graph shows these results?
May/June 2010
The enzyme catalase catalyses the decomposition of hydrogen peroxide into water and oxygen. In an investigation of how pH affects the reaction rate of catalase, potato cubes were placed in hydrogen peroxide. Which dependent variable should be measured?
May/June 2011
Certain inhibitors of enzyme reactions attach to the enzyme / substrate complex. Which of the following statements about this form of inhibition are correct?
May/June 2011
The graphs illustrate how temperature and pH affect enzyme activity. Which statement explains the enzyme activity at the point shown?
May/June 2011
The enzyme catalase catalyses the decomposition of hydrogen peroxide into water and oxygen. In an investigation of how pH affects the rate of reaction of catalase, potato cubes were placed into hydrogen peroxide. Which dependent variable should be measured and recorded?
May/June 2011
Catalase is an enzyme that speeds up the breakdown of hydrogen peroxide into water and oxygen. Two students investigated how enzyme concentration affects the rate of reaction of catalase. They predicted that their results would follow the same pattern. The graphs display the rates measured by each student. Which statement accounts for the different pattern shown by student 2’s results?
May/June 2012
Catalase is an enzyme that speeds up the conversion of hydrogen peroxide into water and oxygen. Two students investigated how enzyme concentration affects the reaction rate of catalase. The students predicted that their results would display the same pattern. The graphs show the rates measured by each student. Which statement explains the different pattern shown by student 2’s results?
May/June 2012
Four students, 1, 2, 3 and 4, counted how many oxygen bubbles were released during an investigation into the effect of catalase from plant tissue on hydrogen peroxide. Each student repeated the experiment five times and found the mean number of bubbles per minute. Which have correctly calculated the mean? (A table is shown of students, raw data in bubbles minute$^{-1}$, and calculated mean values.)
May/June 2013
The diagram illustrates a metabolic pathway. reactant $\xrightarrow{\text{enzyme 1}}$ substance X $\xrightarrow{\text{enzyme 2}}$ substance Y $\xrightarrow{\text{enzyme 3}}$ end product What would happen if a small quantity of a non-competitive inhibitor of enzyme 2 were introduced?
May/June 2013
When examining the rate of reaction of the enzyme lipase in the hydrolysis of triglycerides, pH must be kept at an optimum to stop the lipase denaturing. What is the reason for this?
May/June 2013
In the presence of a competitive inhibitor, how does a rise in substrate concentration influence the rate of an enzyme-catalysed reaction?
May/June 2013
The effect of catalase on hydrogen peroxide was investigated by four students. At the start of the experiment, each student began a digital timer and then stopped it once 25 bubbles had been counted. The reading shown by the digital timer is given below. hours: 00, minutes: 01, seconds: 33, hundredths: 54 Which student obtained results with the greatest precision for the apparatus used?
May/June 2013
The malarial parasite, Plasmodium, enters red blood cells and degrades haemoglobin. Unbound haem groups are poisonous to Plasmodium, so the parasite changes them into non-toxic, crystalline haemozoin by means of an enzyme, HDP, that occurs in every species of Plasmodium. What would be the long term effect of treating patients with malaria with a drug that inhibits HDP?
May/June 2014
The graph plots the rate of activity of the enzyme sucrase against sucrose concentration. What is the reason that the rate of enzyme activity stays unchanged between $80$-$90\ \text{g dm}^{-3}$?
May/June 2014
Which graph illustrates the effect of a non-competitive inhibitor?
May/June 2014
Which statements about the effect of all enzyme inhibitors are correct?
May/June 2015
The graphs illustrate the rate of an enzyme-catalysed reaction. Which graph shows the effect of increasing the concentration of the substrate at two concentrations of a competitive inhibitor?
May/June 2015
Which of the following statements about the optimum temperature of all enzymes are correct?
May/June 2015
Certain enzyme inhibitors attach to the enzyme-substrate complex. Which of the following statements correctly describe this form of inhibition?
May/June 2015
The enzyme DNA polymerase functions in DNA replication. It was obtained from bacteria that inhabit natural hot water springs, where the water temperature lies between $85^{\circ}\text{C}$ and $95^{\circ}\text{C}$. Which graph would show the link between temperature and the rate of DNA replication when it is catalysed by the enzyme from these bacteria?
May/June 2015
Which effect might be caused by a lower concentration of carbonic anhydrase?
May/June 2015
The graph illustrates how raising substrate concentration affects the rate of an enzyme-catalysed reaction. What is limiting the rate of the enzyme-catalysed reaction at 1, 2, 3 and 4 on the graph?
May/June 2016
In two investigations, the rate of an enzyme-catalysed reaction was measured when either a competitive inhibitor or a non-competitive inhibitor was present. What could happen to each rate of reaction if the substrate concentration is increased?
May/June 2016
In an experiment, enzymes X and Y were tested. Enzyme X came from bacteria living in rivers and lakes at temperatures from $5\,^{\circ}\text{C}$ to $20\,^{\circ}\text{C}$. Enzyme Y came from bacteria living in hot water springs at temperatures from $40\,^{\circ}\text{C}$ to $85\,^{\circ}\text{C}$. The experiment recorded the concentration of product made by each enzyme at temperatures between $0\,^{\circ}\text{C}$ and $100\,^{\circ}\text{C}$ after 5 minutes. Which graph shows the results?
May/June 2016
As the temperature of an enzyme is raised, which bond will be the last one to break?
May/June 2016
The influence of substrate concentration on an enzyme-catalysed reaction was recorded under three separate conditions: • without inhibitor • with inhibitor X • with inhibitor Y. The graph presents the data. Which statement is correct?
May/June 2016
A student performed experiments to study how enzyme concentration affects the rate of hydrolysis (break down) of protein in milk. After the enzyme and milk were combined, the protein was hydrolysed and the mixture went from cloudy to clear. The student used five different enzyme concentrations and measured the time needed to reach the end-point for each one. What would be an appropriate control for this investigation?
May/June 2017
The graph illustrates how temperature affects the rate at which the enzyme in a biological washing powder breaks down and removes fruit juice stains. Which statements account for the graph’s pattern at temperatures above X?
May/June 2017
Invertase is the enzyme that catalyses the breakdown of sucrose into glucose and fructose. Three different enzyme inhibitors of invertase, X, Y and Z, were studied. The percentage inhibition of invertase was recorded at a range of inhibitor concentrations. The graph shows the findings of the investigation. Which conclusions are valid from these results?
May/June 2017
The graph presents the outcomes of investigations into the effect of amylase on the hydrolysis of starch at three different temperatures. In each investigation, the concentration and volume of the solutions were kept constant. Which conclusion can be drawn?
May/June 2017
The graph shows how temperature affects the activity of the protease enzyme papain, both when it is dissolved in solution (free) and when it is trapped in alginate beads. Which statement correctly describes the effect of immobilising papain?
May/June 2017
Which words from the table best fill the gaps in the paragraph about enzymes? If the pH of a setting falls below an enzyme’s optimum pH, ……1…… bonds joining neighbouring ……2…… groups that maintain the ……3…… structure are broken.
May/June 2018
The influence of substrate concentration on an enzyme-catalysed reaction was recorded under three separate conditions: • with no inhibitor • with a competitive inhibitor • with a non-competitive inhibitor. The graph illustrates the outcomes. Which statement is correct?
May/June 2018
Which effect could result from a lower concentration of carbonic anhydrase?
May/June 2018
A student performed an investigation into how temperature affects the rate of an enzyme-catalysed reaction. At each temperature, the substrate concentration was measured after $10$ minutes. All the other variables were kept constant. Which graph shows the effect of increasing temperature on the substrate concentration after $10$ minutes?
May/June 2018
The graph illustrates how the rate of an enzyme-catalysed reaction varies with substrate concentration. Determine the Michaelis-Menten constant ($K_m$) for this enzyme under these conditions?
May/June 2018
Four students carried out an investigation into how catalase affects hydrogen peroxide. At the start of the experiment, each student switched on a digital timer and stopped it once 25 bubbles had been counted. The reading on the digital timer is shown below. hours 00, minutes 01, seconds 33, hundredths of a second 54. Which of the times recorded by the students is appropriate for this experiment?
May/June 2018
Emphysema is one form of chronic obstructive pulmonary disease, COPD. In people who have emphysema, the concentration of a plasma protein that blocks the enzyme elastase is very low. Elastase breaks down the elastic fibres in the bronchioles and alveoli. Which of the following are consequences of the reduced inhibitor level in people with emphysema?
May/June 2018
In an investigation, an equal concentration of the enzyme phosphorylase was mixed with different concentrations of glucose phosphate and left at $30^\circ\text{C}$. At intervals of $1$ minute, a single drop of the reaction mixture was taken and placed onto a drop of iodine solution on a white tile. The diagram presents the outcomes of this investigation. What accounts for the pattern seen in the results of this investigation?
May/June 2019
Which statement about competitive inhibitors of enzymes is correct?
May/June 2019
The diagram illustrates a metabolic pathway. Reactant $\xrightarrow{\text{enzyme 1}}$ substance X $\xrightarrow{\text{enzyme 2}}$ substance Y $\xrightarrow{\text{enzyme 3}}$ end product. What would happen if a small quantity of a non-competitive inhibitor of enzyme 2 were added?
May/June 2020
Two enzymes are introduced into a solution containing a low concentration of a substrate that both can use. Which statement is correct?
May/June 2020
Two experiments, X and Y, were performed with an enzyme obtained from humans. In experiment X, the temperature was kept constant at $37^{\circ}\text{C}$. For experiment Y, the temperature rose from $37^{\circ}\text{C}$ to $80^{\circ}\text{C}$. Every other variable was unchanged. Which graph represents the results?
May/June 2020
Which factor influences the rate of an enzyme-catalysed reaction when a non-competitive inhibitor is present? 1 the concentration of enzyme 2 the concentration of inhibitor 3 the concentration of substrate
May/June 2020
The enzyme trypsin hydrolyses proteins to amino acids, but it does not work when the pH is very low because its 3D shape would alter. What causes this change in 3D shape?
May/June 2020
An investigation examined how temperature affects enzyme activity both when the enzyme is immobilised and when it is non-immobilised (free in solution). The product formed by the enzyme-catalysed reaction leads to a fall in pH. The graph presents the outcomes of the investigation. Which condition would produce the greatest yield of product?
May/June 2021
What is one feature of competitive enzyme inhibition?
May/June 2022
The graph illustrates how an increase in substrate concentration affects the rate of an enzyme-catalysed reaction. Line P shows the outcome when the enzyme is used at its optimum pH and optimum temperature, with no inhibitor present. Line Q shows the outcome when the reaction conditions are altered. Which descriptions of changes to the reaction conditions could produce line Q if all the other conditions remained unchanged? 1. Introduce an inhibitor that binds to a site other than the active site. 2. Introduce an inhibitor with a shape similar to the substrate. 3. Introduce an inhibitor that prevents the active site of the enzyme from working. 4. Perform the reaction at a higher temperature.
May/June 2023
Which reactions would have their rate reduced by an inhibitor of carbonic anhydrase?
May/June 2023
A student carried out an investigation into how substrate concentration affects the rate of an enzyme-catalysed reaction. A graph was drawn to display the link between these two variables. The student was told to read values from the graph that could then be used to find the Michaelis-Menten constant, $K_m$, for this enzyme. J, K, L and M mark points taken from the graphs that the student could use to find the value of $K_m$. Which two readings does the student need to use to determine the value of $K_m$?
May/June 2023
The graph illustrates the pattern for an enzyme-catalysed reaction. Which labels are right for the x-axis and the y-axis?
May/June 2024
In what way does the antibiotic penicillin affect the metabolism of a bacterial cell?
May/June 2024
The graph illustrates how substrate concentration affects the reaction rates of three enzymes, X, Y, and Z. What is the correct sequence of the affinity of these enzymes for their substrates, beginning with the enzyme that has the greatest affinity?
May/June 2024
The influence of substrate concentration on an enzyme-catalysed reaction was investigated under three separate conditions: • no inhibitor was present • a competitive inhibitor was present • a non-competitive inhibitor was present. The results are shown in the graph. Which row is correct?
May/June 2024
The graph illustrates how raising substrate concentration affects the reaction rate of two enzymes that catalyse reactions using the same substrate. Which statement is the correct one?
May/June 2025
Which graphs could be used to show how pH affects the rate of enzyme-catalysed reactions?
May/June 2025
Following a heart attack, the enzyme lactate dehydrogenase passes into the blood plasma from injured heart muscle. What is needed to measure the activity of lactate dehydrogenase activity in a sample of blood plasma?
May/June 2025
The action of an enzyme can be influenced by a competitive inhibitor. Which row gives the correct effect of a competitive inhibitor on the value of $K_m$ and the reason for this?
May/June 2025
An investigation was conducted to determine whether compound X could increase the thermostability of an enzyme. Thermostable enzymes work well at high temperatures. The findings from the investigation are given. Which row is the correct one?
May/June 2025
The table presents the findings from an investigation into how temperature affects an enzyme-catalysed reaction. All other variables were kept constant. What is the correct conclusion?
May/June 2025
The graph illustrates how reaction rate varies with substrate concentration for the following conditions: • no inhibitor added • inhibitor X • inhibitor Y. One inhibitor acts competitively, whereas the other is non-competitive. Which estimate of $K_m$ is correct for the reaction shown if a competitive inhibitor is present?
May/June 2025
Diastase is an enzyme which converts starch into maltose. A starch sample is treated with boiled diastase and then left for 15 minutes. The resulting mixture is tested using iodine solution and Benedict’s solution. Which outcome is correct?
May/June 2025
The speed of enzyme-catalysed reactions in human cells is controlled. Which of these may be part of that control?
Oct/Nov 2010
A fixed volume of the enzyme catalase was mixed with a fixed volume of hydrogen peroxide solution. The diagram illustrates how the reaction rate changed as the reaction proceeded. Why did the actual rate of reaction fall as time passed?
Oct/Nov 2010
Which diseases are able to be cured through the use of antibiotics?
Oct/Nov 2010
The rate of enzyme-catalysed reactions in human cells is controlled. Which of these may be involved in this control?
Oct/Nov 2010
Which statements about the effects of all enzyme inhibitors are correct?
Oct/Nov 2011
In an enzyme-catalysed reaction, which pairing of inhibitor and substrate would produce the greatest rate of reaction?
Oct/Nov 2011
After a heart attack, the enzyme lactate dehydrogenase enters the blood plasma from injured heart muscle. Which steps are needed to obtain the most accurate estimate of lactate dehydrogenase activity in a sample of blood plasma?
Oct/Nov 2011
Which of the following statements about the effect of all enzyme inhibitors are correct?
Oct/Nov 2011
As the temperature of an enzyme is increased, which bond will break last?
Oct/Nov 2012
Two enzyme investigations were performed. In the first one, experiment X, the temperature was $37^\circ\text{C}$. In the second investigation, the temperature was raised to $80^\circ\text{C}$. Every other condition stayed unchanged. Which graph represents the results?
Oct/Nov 2012
When an enzyme is heated, which bonds are broken last?
Oct/Nov 2012
At $50^{\circ}\text{C}$, an enzyme is totally denatured. A fixed concentration of this enzyme is mixed with a fixed concentration of its substrate. The time required for the reaction to finish is recorded at several different temperatures. Which graph shows the results?
Oct/Nov 2013
Which statement is correct for a non-competitive inhibitor of enzyme action?
Oct/Nov 2013
Why do large increases in temperature or pH change enzyme activity?
Oct/Nov 2014
Which terms in the table correctly finish the paragraph about enzymes? When the pH of a surrounding environment falls below an enzyme’s optimum pH, ……… between neighbouring ……… groups, which maintain the ……… structure, are broken.
Oct/Nov 2014
Lipase is a digestive enzyme made by the pancreas that catalyses the hydrolysis of dietary lipids. The graph indicates how the pH of a liquid food with a large lipid content falls over time. Which statements could explain the experimental results between 50 and 60 minutes?
Oct/Nov 2014
The statements concern polio and tuberculosis (TB). Which statement explains why the polio vaccine can be given by mouth whereas the TB vaccine must be injected?
Oct/Nov 2014
Which of the following statements concerning enzyme inhibitors are correct?
Oct/Nov 2015
The diagram illustrates the mass of product formed over time in three reactions that use the same substrate and enzyme. The volumes of substrate and enzyme, together with the temperature, were kept the same in each reaction. Which statement accounts for the difference in these reactions?
Oct/Nov 2015
Tyrosinase is an enzyme that speeds up the transformation of the amino acid tyrosine into the black pigment melanin. It causes the black fur colour seen in some rabbits. When one set of rabbits was maintained at $30^{\circ}\text{C}$, $90\%$ of them had light fur colour. When a different set of rabbits was kept at $10^{\circ}\text{C}$, $90\%$ of them had black fur colour. Which hypothesis do these results support?
Oct/Nov 2015
Why must a person who has a bacterial infection take antibiotics at regular, evenly spaced intervals?
Oct/Nov 2015
Line X shows how an enzyme-catalysed reaction proceeds under optimum conditions. Line Y illustrates the action of the same enzyme on the same substrate, but with one variable altered: substrate concentration or pH or temperature. Which changes to the variables could produce the result shown by line Y?
Oct/Nov 2015
In the aftermath of a heart attack, damaged heart muscle allows the enzyme lactate dehydrogenase to enter the blood plasma. Which steps must be taken to estimate lactate dehydrogenase activity in a sample of blood plasma?
Oct/Nov 2016
Two experiments were done with an enzyme from humans. In the first experiment, X, the temperature was kept constant at $37^b0\text{C}$. In the second experiment, the temperature was raised from $37^b0\text{C}$ to $80^b0\text{C}$. Every other factor remained unchanged. Which graph represents the results?
Oct/Nov 2016
The graph presents findings from an investigation into how amylase acts on starch at three different temperatures. Which statements are valid conclusions from these results?
Oct/Nov 2016
An investigation was carried out into the speed of an enzyme-catalysed reaction. In the investigation, the concentration of the substrate was maintained above the concentration of the enzyme. In this investigation, which change to the variables would always cause the reaction rate to increase?
Oct/Nov 2016