Lesson 3.1.4.2.1

3.1.4.2.1 Enzyme action and activation energy Quiz: AQA Biology, Unit 1

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

In partnership with Revision Ninja

Lesson 3.1.4.2.1, Enzyme action and activation energy: 20 multiple choice questions for the AQA Biology (7402), Unit 1: Biological molecules, written with Revision Ninja.

Host it live on the board and students join with a game code on their own devices, or revise alone with Free Play. The answers are revealed in the game.

Host this setFree Play

The 20 questions

  1. What is activation energy?

    • The energy stored in the chemical bonds of the product molecules formed by the reaction
    • The minimum energy that colliding molecules must have for a reaction to occur
    • The energy supplied by an enzyme to the substrate molecules so that they can be converted
    • The total energy released when a reaction is complete and the products have reached equilibrium

  2. What effect does an enzyme have on the activation energy of the reaction it catalyses?

    • It has no effect on the activation energy
    • It lowers the activation energy
    • It raises the activation energy
    • It doubles the activation energy

  3. What is the active site of an enzyme?

    • The whole surface of the enzyme that is hydrophobic
    • The point where the enzyme is attached to the cell membrane
    • The region of the enzyme that is always occupied by a cofactor
    • The region of the enzyme whose shape is complementary to a specific substrate

  4. Which model proposes that the active site changes shape to fit the substrate more closely?

    • Collision model
    • Lock-and-key model
    • Induced-fit model
    • Competitive model

  5. Which description of an enzyme is correct?

    • A substrate that is converted into a product during the reaction
    • A non-protein catalyst that is consumed by the reaction it catalyses
    • A fatty acid that lowers the activation energy by bonding to the substrate
    • A biological catalyst, usually a protein, that is not used up in the reaction it catalyses

  6. What is an enzyme-substrate complex?

    • A permanent bond between the enzyme and the product
    • A stable product that is released from the active site after reaction
    • A structure formed when two enzymes bind to one substrate permanently with no exceptions
    • A temporary structure formed when the substrate binds to the active site

  7. What does the specificity of an enzyme depend on?

    • The temperature of the surroundings only, and not the shape of the enzyme molecule itself
    • The number of substrate molecules present in the cell at the time that the reaction takes place with no exceptions
    • The number of phosphate groups that happen to be attached to the surface of the enzyme molecule
    • The shape and chemical properties of its active site, which must be complementary to the substrate

  8. An enzyme-catalysed reaction is compared with the same reaction uncatalysed. Which statement about the enthalpy change is correct?

    • The enzyme makes the overall energy change more exothermic
    • The enzyme makes the overall energy change more endothermic
    • The enzyme does not change the overall energy change of the reaction
    • The enzyme removes the energy change, so the reaction becomes energy-neutral

  9. Without an enzyme, a reaction has an activation energy of 50 kJ/mol. With an enzyme the activation energy is 25 kJ/mol. By how much is the activation energy lowered?

    • 50 kJ/mol
    • 75 kJ/mol
    • 10 kJ/mol
    • 25 kJ/mol

  10. Why does adding an enzyme increase the rate of a reaction?

    • Enzymes increase the number of collisions by making molecules larger
    • Enzymes add energy to the substrate, so each molecule has more kinetic energy
    • Enzymes raise the temperature of the reaction mixture locally
    • A larger proportion of molecules have energy at or above the lower activation energy

  11. Amylase breaks down starch but does not break down cellulose. Which explanation is most accurate?

    • Cellulose contains phosphate groups that stick to the surface and block the active site completely
    • Starch is a protein, which amylase digests, whereas cellulose is a lipid that amylase cannot digest
    • Cellulose is too hydrophobic to dissolve in the aqueous enzyme solution used in the experiment
    • Amylase's active site is complementary to alpha-linked starch and not to beta-linked cellulose

  12. In the lock-and-key model, what is the relationship between the enzyme and substrate?

    • The substrate has no fixed shape of its own and so fits any active site that it happens to meet
    • The enzyme and the substrate both change shape in order to form a new bond with each other
    • The enzyme forms a covalent bond with the substrate, and this bond is then broken in the reaction
    • The enzyme has a rigid active site that is exactly complementary in shape to the substrate

  13. Which statement correctly describes the enzyme in an enzyme-catalysed reaction?

    • It is recovered unchanged at the end of the reaction and can catalyse further reactions
    • It is converted into the product of the reaction, so it cannot be reused by the cell afterwards
    • It is consumed in the reaction, so it must be replaced continuously in the cell for reactions to go on
    • It is used up only when the substrate concentration is very high, and not at any other time

  14. Why does the enzyme-substrate complex lower the energy barrier of a reaction?

    • It converts the substrate into a stable product before the reaction begins
    • It supplies heat to the substrate, raising its temperature until the reaction starts
    • It holds substrates in a favourable orientation and can strain bonds, so less energy is needed to react
    • It increases the mass of the substrate, so collisions are more energetic

  15. An enzyme-catalysed reaction proceeds at body temperature. Why would the uncatalysed reaction be too slow to sustain life at that temperature?

    • The uncatalysed reaction only occurs at temperatures above 100 C, which are never reached in the body
    • The uncatalysed reaction requires one molecule of ATP to be used for every single collision that occurs
    • The uncatalysed reaction has a high activation energy, so few molecules have enough energy to react at body temperature
    • The uncatalysed reaction releases too little energy to be useful to the cell at body temperature

  16. A student claims that enzymes increase the energy available to molecules in a reaction. Which evaluation is correct?

    • Incorrect, because enzymes increase the energy of the products beyond that of the reactants with no exceptions
    • Correct, because lower activation energy means more energy is available to the substrate
    • Correct, because enzymes release the energy stored in the active site
    • Incorrect, because enzymes lower the activation energy but do not supply energy to the molecules

  17. A reaction is catalysed by an enzyme. Why does the enzyme not change the position of equilibrium of the reaction?

    • A catalyst removes the products as they are formed, so equilibrium cannot be reached
    • A catalyst changes the enthalpy change of the reaction, which alters equilibrium
    • A catalyst speeds up both the forward and the reverse reaction equally
    • A catalyst stops the reverse reaction, so the forward reaction is favoured

  18. An enzyme's rate doubles for every 10 C rise in temperature, below its optimum. If the rate at 20 C is 4 units, what is the rate at 40 C?

    • 20 units
    • 12 units
    • 8 units
    • 16 units

  19. Explain how the induced-fit model accounts for the specificity of an enzyme while still allowing a tight fit to the substrate.

    • The active site changes shape on binding to every molecule that approaches it, so specificity is entirely lost
    • The active site is flexible and changes shape on binding, moulding around the substrate, so only correct substrates bind well
    • The active site is rigid and only fits a substrate that has exactly the same overall mass as the enzyme
    • The substrate changes shape to fit any active site that it meets, so the enzyme needs no specificity at all

  20. If substrate concentration and all other conditions are kept constant, what happens to the rate of reaction when the enzyme concentration is doubled?

    • The rate halves, because the enzymes compete with one another for the substrate
    • The rate is unchanged, because enzymes are only affected by temperature
    • The rate increases only if the enzymes are denatured by the higher concentration
    • The rate increases, because more active sites are available to form enzyme-substrate complexes

All AQA Biology quizzes