Paper 1: Enzyme Practical

Question 1

How is pH controlled?

Answer 1

By adding buffer solutions with different pH values

Question 2

How is the rate of enzymes activity measured?

Answer 2

By testing the enzyme-substrate solution for the presence of starch at fixed intervals, to find the time taken for all starch to be digested

Rate = 1/time or 1000/time

Question 3

How is the presence of starch tested

Answer 3

Using iodine solution

If starch is present, the solution goes from brown to blue-black

Question 4

How can the validity be improved?

Answer 4

By repeating the practical at each pH at least 3 times and take a mean of the time taken to find the rate

Question 5

How can accuracy of the estimate of the optimum pH be improved?

Answer 5

By repeating the practical at smaller pH intervals around the estimated optimum pH

Question 6

State a source of error in this practical

Answer 6

The time intervals between testing may be too long to accurately find the time taken for all the starch to be broken down

Question 7

State a hazard and safety precaution in this practical

Answer 7

Iodine solution is an irritant. Avoid contact with skin and eyes