Enzyme Action and the Active Site · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

One shape, one job

Science · Organisms & Life Processes · ages 14-16
Name ______________________   Date ____________

  1. What is the active site?

    • The energy that starts reactions
    • The pocket where substrate binds
    • The product that leaves

  2. What is an enzyme?

    • A protein catalyst that speeds a reaction
    • A substrate that gets used up
    • A product of digestion

  3. An enzyme is used up by the reaction it runs.

    Circle one:   True   False

  4. What happens to the enzyme once its reaction finishes?

    • It is used up like fuel
    • It turns into product
    • It is unchanged and works again

  5. Why does the starch-breaking enzyme do nothing to protein?

    • Its site fits starch shape, not protein shape
    • Protein is too strong for enzymes
    • Starch blocks the protein away

  6. How do enzymes speed up reactions?

    • By adding heat to the cell
    • By lowering activation energy
    • By changing the products made

  7. An active site changes shape after a mutation. What happens to the rate?

    • It rises, as the site grips tighter
    • It stays the same, as shape does not matter
    • It falls, as the substrate no longer fits

  8. Mia says her enzyme broke because it ran out of strength after one reaction. What is wrong?

    • Enzymes are never proteins
    • Enzymes are not used up
    • Substrates never bind to enzymes
LightMySky · lightmysky.comW1-mt__ozLTPNN0H-s1

Answer key

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

One shape, one job W1-mt__ozLTPNN0H-s1

  1. The pocket where substrate binds · The active site is the shaped pocket where the substrate binds.
  2. A protein catalyst that speeds a reaction · Enzymes are protein catalysts, and catalysts survive the reaction.
  3. False · The enzyme walks away unchanged and catalyses again.
  4. It is unchanged and works again · Catalysts are not consumed, so the enzyme is free for the next substrate.
  5. Its site fits starch shape, not protein shape · Specificity is about shape: the site grips starch and cannot grip protein.
  6. By lowering activation energy · Enzymes lower the starting push, called activation energy, so reactions run faster.
  7. It falls, as the substrate no longer fits · A warped pocket cannot grip its substrate, so the rate falls to nothing.
  8. Enzymes are not used up · Enzymes survive every reaction, so running out of strength cannot happen.
Worksheet · LightMySky