CYTOTOUR

CytoTour › Worksheets › Enzymes

Enzymes worksheet: activation energy, the active site and inhibition

A free, printable worksheet for high school and AP Biology. Students explain how enzymes lower activation energy, predict the effects of temperature, pH and substrate concentration, and compare competitive, noncompetitive and feedback inhibition.

Download the PDF (free)Answer key (Teacher plan)

What's inside

  1. Vocabulary (10 terms)
  2. How enzymes work (5 questions)
  3. The environment (5 questions)
  4. Inhibition and regulation (6 questions)

Teach it with the 3D lesson

Every question matches a step in CytoTour's 3D chapter on enzymes, built from real human enzyme structures — glucokinase and HMG-CoA reductase — at true size. Read the steps with pictures on enzymes, step by step, or project the lesson in class — Chapter 1 is free, Chapters 5 and 7 are free with an account, and the Teacher plan opens every chapter.

The worksheet

This is the printable sheet (17 questions). Printing this page prints only the worksheet.

CytoTour · cytotour.com · free to print and copy for your classes

Enzymes

NameDatePeriod

Part 1 · Vocabulary

1. Write the letter of the matching description next to each term.

  1. Enzyme
  2. Activation energy
  3. Substrate
  4. Active site
  5. Induced fit
  6. Denaturation
  7. Competitive inhibitor
  8. Noncompetitive inhibitor
  9. Feedback inhibition
  10. Cofactor
  1. AAn inorganic ion, such as Mg²⁺ or Zn²⁺, that an enzyme needs
  2. BBinds the active site and blocks the substrate
  3. CA biological catalyst, almost always a protein
  4. DThe molecule an enzyme acts on
  5. EBinds an allosteric site and lowers the maximal rate
  6. FThe enzyme's shape shifts as the substrate binds, giving the best fit
  7. GThe pocket where the substrate binds
  8. HThe energy input a reaction needs to reach its transition state
  9. ILoss of an enzyme's structure — and its ability to catalyze — from heat, pH or chemicals
  10. JA pathway's end product slows an enzyme early in the pathway

Part 2 · How enzymes work

2. How does an enzyme speed up a reaction?

  1. AIt lowers the activation energy
  2. BIt adds energy to the reactants
  3. CIt makes the reaction release more energy
  4. DIt raises the temperature of the cell

3. Sketch an energy diagram for a reaction that releases energy, with and without an enzyme. Label the reactants, the products and the activation energy. What does the enzyme change, and what does it not change?

4. What decides whether a substrate can bind an enzyme's active site?

  1. AIts shape and charge fitting the active site
  2. BIts size alone
  3. CThe temperature only
  4. DWhether the enzyme is already bound to a product

5. How does the induced-fit model differ from the lock-and-key model? Use glucokinase as the example.

6. After glucokinase makes glucose 6-phosphate, what happens to the enzyme?

  1. AIt is unchanged and can bind another glucose
  2. BIt is used up in the reaction
  3. CIt becomes part of the product
  4. DIt denatures

Part 3 · The environment

7. Describe and explain the shape of a graph of reaction rate against temperature for an enzyme.

8. An enzyme is heated well above its optimal temperature. Why does its rate drop?

  1. AIts structure is disrupted (denatured), so the active site no longer works
  2. BMolecules move too slowly to collide
  3. CThe substrate runs out
  4. DHeat raises the activation energy

9. Why does an enzyme work less well outside its optimal pH range?

10. Is denaturation always permanent?

11. How does adding more substrate change the rate of an enzyme-catalyzed reaction?

Part 4 · Inhibition and regulation

12. A statin binds in the active site of HMG-CoA reductase. What kind of inhibitor is it?

  1. ACompetitive
  2. BNoncompetitive
  3. CAllosteric activator
  4. DCoenzyme

13. Compare the two kinds of inhibitor.

Where it bindsEffect on the rateCan more substrate overcome it?
Competitive
Noncompetitive

14. What does an allosteric activator do? Where does it bind?

15. Isoleucine, the end product of a pathway, binds threonine deaminase, an enzyme early in that pathway. What happens?

  1. AThe pathway slows: feedback inhibition
  2. BThe pathway speeds up
  3. CIsoleucine is broken down
  4. DThreonine deaminase makes more isoleucine

16. ATP inhibits, and ADP activates, some enzymes of sugar breakdown. Why is this useful to the cell?

17. What is the difference between a cofactor and a coenzyme? Give one example of each.