Enzymes: how they speed reactions, and what pH and temperature do

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   Enzyme drawing (model, not to scale). Ari’s friend says an enzyme is used up in each reaction, so cells need a fresh enzyme for every substrate. Which response is best?

   • Disagree: an enzyme stays far away from the substrate
   • Agree: part of the enzyme is spent on each substrate it meets
   • Agree: the enzyme turns into the product during the reaction
   • Disagree: the enzyme comes out unchanged, so it is reusable
2. 2.

   Bo’s friend says an enzyme speeds a reaction by giving the substrate the energy it needs. Use the diagram. Which response is best?

   • Agree: the energy it supplies pushes the substrate over the hill
   • Agree: the enzyme stores energy and hands it to the reaction
   • Disagree: it lowers the energy of the products instead
   • Disagree: it lowers the activation energy, so less is needed

3. Read this first

   Use this

   Model drawing, not to scale. Enzyme E has a notch, its active site, shaped to hold a round bead joined to a square bead. Molecule M1: a round bead joined to a square bead. Molecule M2: a round bead joined to a triangle bead.

4. 3.

   Esme’s friend says enzymes are tiny living things, so one can learn to work on any substrate. Which response is best?

   • Disagree: an enzyme is a protein whose active site fits a matching substrate
   • Disagree: an enzyme is a protein, so it fits any substrate equally
   • Agree: living enzymes reshape their active site to fit any substrate
   • Agree: an enzyme is alive because it works inside living cells

5. Use the table

   Investigation card (model data; a teacher handles every chemical). Question: How does temperature affect catalase? What is changed: the temperature of the catalase solution. What is measured: the height of the oxygen foam after 1 minute. What stays the same: 5 mL of catalase solution and 5 mL of hydrogen peroxide in each tube.

   temperature (°C)	foam height (mm)
   10	8
   30	30
   50	12
   80	0

6. 4.

   A teacher ran this catalase test while Jun’s class watched. Which conclusion do the data support?

   • Among the four, 30 °C gave the most foam and 80 °C gave none
   • Catalase was used up at 80 °C, which is why no foam formed
   • More heat gave more foam, so catalase works best above 80 °C
   • 30 °C is exactly the best temperature for catalase
7. 5.

   Kira’s class reads a teacher’s catalase test. What is the flaw in the test?

   • Two things changed at once: the temperature and the catalase amount
   • The catalase in Tube 1 was used up, so the tubes cannot be compared
   • Tube 2 should have been hotter, since heat speeds up enzymes
   • The hydrogen peroxide amount should have changed in each tube
8. 6.

   A teacher added water to Tube 2 on purpose, while Luz’s class watched. What does Tube 2 help show?

   • Catalase is what makes the foam form: water alone made none
   • Catalase turns into foam, since the water tube had none
   • Catalase supplies the energy, since the water tube had none
   • Water stops foam from forming, since the water tube had none

9. Use this

   Rate-versus-substrate graph with and without inhibitor I (model data). Substrate amount (units) across, 0 to 7, a mark every 1. Reaction rate (units per minute) up, 0 to 100, a mark every 20. Enzyme alone joins (0 units, 0), (1 unit, 30), (2 units, 55), (3 units, 75), (4 units, 85), (5 units, 90), (6 units, 90), (7 units, 90) with straight pieces. Enzyme with inhibitor I joins (0 units, 0), (1 unit, 15), (2 units, 32), (3 units, 50), (4 units, 65), (5 units, 78), (6 units, 86), (7 units, 90) with straight pieces. A small drawing beside the graph shows inhibitor I, shaped like the substrate, sitting in the enzyme’s active site.

10. 7.

    Milo sees inhibitor I sit in the enzyme’s active site in the drawing. Using the graph at substrate 2, what does I do, and why?

    • The rate falls, because I changes the substrate’s shape
    • The rate falls, because I takes up active sites
    • The rate rises, because I adds energy to the active sites
    • The rate falls, because I uses up the enzyme over time
11. 8.

    Noah sees the two lines meet at 90 at substrate 7. Which explanation fits both the graph and the drawing of inhibitor I?

    • The extra substrate brings energy that cancels I
    • The extra substrate outcompetes I for active sites
    • I changes into whatever substrate the enzyme fits
    • I is used up by the extra substrate that arrives
12. 9.

    Pia knows inhibitor I fits enzyme E’s active site, not F’s. Using the drawing and the table, which statement is best?

    • I slows both, because an inhibitor blocks any enzyme it meets
    • I speeds F up, because F has no matching active site for I
    • I slows E but not F, because I matches E’s active site
    • I slows E by using E up, while F is left untouched

13. Product made by 5 enzyme molecules (model data)

    time (min)	product molecules
    0	0
    1	1000
    2	2000
    3	3000

14. 10.

    Zee’s tube holds 5 enzyme molecules. The table shows the product made over time. How can 5 enzymes make 3,000 products?

    • Enzymes are alive, so each one makes copies of itself as it works
    • Each enzyme is unchanged, so it can work again and again
    • The enzymes give off energy, which turns into extra product
    • Each enzyme is used up in one reaction, so new enzymes must have formed