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: the enzyme comes out unchanged, so it is reusable
   • Agree: the enzyme turns into the product during the reaction
   • Agree: part of the enzyme is spent on each substrate it meets
   • Disagree: an enzyme stays far away from the substrate
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 enzyme stores energy and hands it to the reaction
   • Disagree: it lowers the activation energy, so less is needed
   • Disagree: it lowers the energy of the products instead
   • Agree: the energy it supplies pushes the substrate over the hill

3. Read this first

   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

4. 3.

   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
   • 30 °C is exactly the best temperature for catalase
   • 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
5. 4.

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

   • The hydrogen peroxide amount should have changed in each tube
   • 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
6. 5.

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

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

7. 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.

8. 6.

   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 rises, because I adds energy to the active sites
   • The rate falls, because I changes the substrate’s shape
   • The rate falls, because I takes up active sites
   • The rate falls, because I uses up the enzyme over time
9. 7.

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

   • I changes into whatever substrate the enzyme fits
   • The extra substrate outcompetes I for active sites
   • The extra substrate brings energy that cancels I
   • I is used up by the extra substrate that arrives
10. 8.

    Ren sees the model enzyme was more active at 40 °C than at 20 °C, but nearly stopped at 60 °C. Which explanation fits the whole graph?

    • The enzyme gave away its energy as it got hotter, so it slowed
    • Heat helps up to a point, then changes the enzyme’s shape
    • Heat speeds reactions, so the 60 °C reading must be a measuring error
    • The enzyme was used up between 40 °C and 60 °C, so rates fell
11. 9.

    In Tala’s test, the rate did not change when the substrate rose from 6 to 7. Which explanation fits the graph?

    • Nearly all active sites were already busy
    • The extra substrate brought energy that slowed the enzyme down
    • The substrate stopped fitting once there was more of it
    • The enzyme was used up by the extra substrate added at 7

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

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

13. 10.

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

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