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Introduction to the lesson
In the last lesson we saw the mode of enzyme action. In this lesson we will see how different factors can make enzyme action faster or slower and how some factors can destroy enzymes altogether. Again, as we look at some of these factors it is important to think of their effect in the context of the general structure of enzymes (which you learned about in ch.2).
Reading
Read the section under the heading “Factors that affect enzyme action” in your text book (p.57-60).
The effect of enzyme concentration
Learning Activity 1
Answer the following questions in your exercise book.
- Describe the effect of enzyme concentration on enzyme action.
- Describe an experiment that would demonstrate the effect of enzyme concentration on enzyme action (take note of Box 3.1 on page 58 about measuring reaction rate).
- Make sure you are able to understand and interpret the graphs on p.58.
- Answer Question 3.1 a and b on page 58 and Question 3.2 on p.59.
The effect of substrate concentration
Learning Activity 2
Answer the following questions in your exercise book.
- Draw a sketch of the graph given in Fig. 3.8 on p.59. Using the sketch of the graph describe the effect of substrate concentration on enzyme action.
- Explain Vmax.
- Answer Question 3.3 on p.59.
The effect of temperature on enzyme activity
Learning Activity 3
Answer the following questions in your exercise book.
- Explain the effect of temperature on the rate of an enzyme-controlled reaction. Use the graph in Fig. 3.9 in your explanation.
- What happens to the enzymes when the temperature is increased to above the optimum temperature? Can you explain this in terms of protein structure and the bonds that hold the protein's 3D structure together?
The effect of pH on enzyme activity
Learning Activity 4
Answer the following questions in your exercise book.
- What is pH?
- What pH do most enzymes (but not all) work best in?
- What happens to the structure of enzymes if the pH is too low? Explain this in terms of hydrogen ions and the R groups of the amino acids in the enzyme.
- What does one use when investigating pH and why?
Definitions and review
Definitions
- Vmax
- Denatured
- Optimum temperature
- pH
- Optimum pH
Mindmap
Add this section to your chapter three mindmap.