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Introduction to the lesson
In the past two lessons we have learned about how enzymes act and what factors can increase or decrease their effectiveness. In this lesson we will see how enzymes can be inhibited, either permanently or temporarily. We will see how they are inhibited, the different kinds of inhibition and some broad effects of enzyme inhibition. This is an important lesson and, though confusing at first, is really quite simple when you understand it so work carefully through it and make sure you grasp the concepts.
Competitive, reversible inhibition
Read the section under the heading "Competitive, reversible inhibitors" in your text book (p.61).
Learning Activity 1
Answer the following questions in your exercise book.
- Explain how a competitive inhibitor works to inhibit an enzyme.
- Reversible means that the inhibition is only temporary, not permanent. Explain why competitive inhibition cannot be irreversible.
- Enzyme inhibition can sometimes be a good thing. Explain how competitive inhibition can save the life of a person who has accidentally drunk antifreeze (i.e. Ethylene glycol).
Non-competitive, reversible inhibition
Read the section under the heading "Non-competitive, reversible inhibition" in your text book (p.61-62).
- Take note: there is another type of inhibition called non-competitive, irreversible inhibition. This is when an inhibitor bind permanently to the active site of an enzyme. It is irreversible because it the inhibitor binds permanently to the enzyme. It is non-competitive because, being irreversible, the inhibition cannot be reversed by increasing the concentration of the substrate.
Learning Activity 2
Answer the following questions in your exercise book.
- Where does a non-competitive, reversible inhibitor combine with the enzyme?
- Explain how the non-competitive, reversible inhibitor binds with the enzyme in terms of protein structure.
- Explain end-product inhibition. Draw a diagram and describe each step. (cf. Fig. 3.13 pm p.61 of your textbook).
Definitions and review
Definitions
- Enzyme inhibitor
- Competitive inhibition
- Non-competitive inhibition
- Reversible inhibition
- Irreversible inhibition
- End-product inhibition
Mindmap
Add this section to your chapter three mindmap.