Factors affecting enzyme concentration

1. Factors affecting enzyme concentration

2. Enzymes: true or false?

3. Spec Check • explain the importance of cofactors and coenzymes in enzyme-controlled reactions;

4. What are cofactors? Some enzymes require the addition of a non-protein substance called a cofactor before they can catalyze a reaction. There are two main types of cofactor: • activators – inorganic groups that are permanently bound to the enzyme and so are a type of prosthetic group. Common examples include iron, zinc and copper. • coenzymes – organic molecules that bind only temporarily to the enzyme, transferring a chemical group necessary required for the reaction. Examples include vitamin C and ATP. vitamin C

5. Spec Check • describe and explain the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity; • describe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can be investigated experimentally;

6. Enzyme Experiments • Measuring effects on enzymes: • Measure the amount of product made or substrate used up. • Can be done by • Measuring the amount after a fixed period • Measuring the amount at pre-determined time intervals • If you measure time taken for something you can then calculate the rate of reaction by 1/time

7. Next.... • Plot a graph Rate of reaction Independent variable

8. Controlled factors in experiments • Equilibration – incubating the substrate and the enzyme before the start of the experiment to ensure they reach the required temperature before the experiment begins • Control all other factors except the one being investigated • Eg accurate measurements, temperature, pH

9. Calculating initial rate • This is important if you want to compare the rate of a reaction with the rate after a factor has been altered.

10. Measuring the initial rate of reaction

11. Explaining and measuring enzyme activity

12. Effect of temperature on enzymes

13. Effect of pH on enzymes

14. Rate of reaction experiment

15. Effect of substrate concentration on rate

16. Effect of enzyme concentration on rate

17. Now complete the rest of the table • Use the activity sheet pack per group • Use p142-3 in purple books • Use p 138 in green books • You must know a method to measure enzyme activity for each factor

18. Factors affecting rate of reaction

19. Spec Check • (f) explain the effects of competitive and non-competitive inhibitors on the rate of enzyme-controlled reactions, with reference to both reversible and non-reversible inhibitors; • (g) explain the importance of cofactors and coenzymes in enzyme-controlled reactions; • (h) state that metabolic poisons may be enzyme inhibitors, and describe the action of one named poison; • (i) state that some medicinal drugs work by inhibiting the activity of enzymes (HSW6a).