Measuring the Rate of an Enzyme Reaction · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Clock the enzyme, read the hump

Science · Organisms & Life Processes · ages 15-16
Name ______________________   Date ____________

  1. Why does heating usually speed a reaction?

    • Molecules collide harder and more often
    • Heat eats the reactants
    • Thermometers push molecules

  2. A colour change takes 50 seconds. Using rate as 1000 divided by seconds, what is the rate?

    Answer: ______________

  3. The rate falls after the optimum because the enzyme gets used up.

    Circle one:   True   False

  4. You count 30 bubbles in 60 seconds. What is the rate in bubbles per second?

    Answer: ______________

  5. Where do you mark the optimum on a rate sketch?

    • Where the curve starts
    • Where the axes cross
    • Where the curve peaks

  6. Pepsin works in the stomach and amylase in the mouth. What follows?

    • Both prefer neutral conditions
    • Each enzyme loves its own pH: acid for pepsin, neutral for amylase
    • pH never affects enzymes

  7. Two runs differ only in temperature, and run B has the steeper slope. What can you say?

    • Run B is faster, and heat is the likely reason
    • Run B used more enzyme
    • Steeper slopes mean slower rates

  8. An enzyme is boiled, cooled, then tested. The rate stays near zero. Why?

    • Cooling was too slow
    • The active site was permanently scrambled, so recovery is impossible
    • Boiling removes the substrate
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Clock the enzyme, read the hump W1-mt_Rmz54ICmRC-s1

  1. Molecules collide harder and more often · Faster molecules meet harder and more often, so more collisions react.
  2. 20 · Divide 1000 by the seconds: 1000 divided by 50 is 20.
  3. False · The fall comes from a scrambled active site, not a spent enzyme.
  4. 0.5 · Change per time: 30 divided by 60 is 0.5 bubbles per second.
  5. Where the curve peaks · The optimum is the top of the hump, where the rate is highest.
  6. Each enzyme loves its own pH: acid for pepsin, neutral for amylase · One pH never suits all: each enzyme peaks where it lives.
  7. Run B is faster, and heat is the likely reason · One dial changed and the slope steepened, so heat sped it up.
  8. The active site was permanently scrambled, so recovery is impossible · Denaturing past the optimum never reverses on cooling.
Worksheet · LightMySky