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

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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.

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The 20 questions

  1. What is the minimum energy required for a reaction to start called?

    • Enthalpy change
    • Activation energy
    • Binding energy
    • Kinetic energy

  2. How do enzymes affect the activation energy of a reaction?

    • They double it
    • They lower it
    • They raise it
    • No effect

  3. Which region of an enzyme molecule binds to the substrate?

    • Variable region
    • Binding pocket
    • Allosteric site
    • Active site

  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. What type of biological macromolecule are almost all enzymes?

    • Lipids
    • Carbohydrates
    • Nucleic acids
    • Proteins

  6. What temporary structure forms when a substrate binds to an active site?

    • Enzyme-product complex
    • Transition complex
    • Allosteric complex
    • Enzyme-substrate complex

  7. Which structural feature primarily determines the specificity of an enzyme?

    • Primary sequence length
    • Overall mass
    • Peptide bond count
    • Active site shape

  8. How does an enzyme affect the overall enthalpy change of a reaction?

    • Increased
    • Decreased
    • Unchanged
    • Reduced to zero

  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 lowering activation energy increase the rate of reaction?

    • Increased substrate concentration
    • Higher kinetic energy
    • Higher collision speed
    • More successful collisions

  11. Why does amylase hydrolyse starch but not cellulose?

    • Lack of energy
    • Competitive inhibition
    • Denaturation by cellulose
    • Active site specificity

  12. In the lock-and-key model, how is the active site described?

    • Denatured and open
    • Flexible and adaptive
    • Non-complementary
    • Rigid and complementary

  13. What happens to an enzyme molecule at the end of a reaction?

    • Unchanged and reusable
    • Fully consumed
    • Permanently altered
    • Broken down completely

  14. How does forming an enzyme-substrate complex lower activation energy?

    • Absorbs thermal energy
    • Supplies kinetic energy
    • Strains substrate bonds
    • Raises system temperature

  15. Why are uncatalysed biological reactions usually too slow to sustain life?

    • Rapid denaturation
    • Insufficient substrates
    • High activation energy
    • Low kinetic energy

  16. Do enzymes add chemical energy to substrate molecules during a catalysed reaction?

    • Only at high temperatures
    • Yes
    • Only sometimes
    • No

  17. How does an enzyme affect the equilibrium position of a reversible reaction?

    • Shifts to products
    • Prevents equilibrium
    • Unchanged
    • Shifts to reactants

  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. According to the induced-fit model, what happens to the active site when a substrate binds?

    • It denatures permanently
    • It changes shape
    • It remains rigid
    • It breaks down

  20. What happens to the reaction rate when enzyme concentration is doubled with excess substrate?

    • It halves
    • It stays constant
    • It quadruples
    • It doubles

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