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Factors Affecting Enzyme Activity

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Presentation on theme: "Factors Affecting Enzyme Activity"— Presentation transcript:

1 Factors Affecting Enzyme Activity

2 Learning Outcomes apply knowledge of proteins to explain the effects on enzyme activity of: pH temperature substrate concentration enzyme concentration competitive inhibitors, and non-competitive inhibitors including heavy metals differentiate between the roles of enzymes and coenzymes in biochemical reactions identify the role of vitamins as coenzymes

3 Factors affecting enzyme activity
Temperature pH Concentration Activation Inhibitors Co-enzymes

4 What happens to the rate of most chemical reactions as the temperature is increased?

5 Temperature All enzymes have an optimal temperature
Up to this temperature, the reaction rate increases as temperature increases Above this temperature, denaturation of the enzyme occurs (irreversible)

6 What would you expect to be the optimal temperature of enzymes that function in the human body?

7 Effect of temperature on enzyme activity
Optimal temperature Enzyme activity Temperature

8 How might a strong acid or base affect a protein?

9 pH All enzymes have an optimal pH
High or low pH causes reduced enzyme activity and denaturation of the enzyme

10 Effect of pH on enzyme activity
Optimal pH Enzyme activity pH

11 Fig. 6.8

12 What happens if we increase or decrease the concentration of substrate?

13 Substrate concentration
Increasing the substrate concentration increases the reaction rate only to the point where all enzymes are being used

14 Effect of substrate concentration
Enzyme activity Substrate concentration

15 What if we add more enzyme?
How would this happen in the body?

16 Enzyme concentration In cells, enzyme concentration is genetically controlled (control of protein synthesis) Increasing the amount of enzyme will increase the reaction rate (as long as substrate is present)

17 Effect of enzyme concentration
Enzyme activity Enzyme concentration

18 Activation Enzymes may be “turned on” by the presence of another molecule (ex. The addition of a phosphate group, known as phosphorylation)

19 Enzyme activation

20 How could you prevent a substrate from binding to an enzyme active site?
Would this ever be a desirable outcome?

21 Inhibition Inhibitors are molecules other than the substrate that bind to the enzyme and inhibit its activity

22 Competitive inhibition
Competitive inhibitors compete with the substrate by binding to the active site

23 Non-competitive inhibition
Non-competitive inhibitors bind to a different site on the enzyme (allosteric site) Change the shape of the enzyme’s active site

24 Toxic heavy metals such as lead, cadmium and mercury can bind to enzymes causing denaturation
Act as non-competitive inhibitors

25 Feedback inhibition Sometimes the product of the pathway acts as an inhibitor This stops the pathway when there is enough of the product

26 Fig. 6.9a

27 Fig. 6.9b

28 Enzyme cofactors Cofactors or coenzymes are non-protein molecules that assist the enzyme May be inorganic ions ex. Copper, zinc, or iron Often are organic molecules derived from vitamins Function is often to transfer electrons or functional groups (ex. Phosphate) to the substrate

29 Vitamin deficiency results in interference with enzyme activity in various metabolic pathways
(so eat your veggies!)

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