Factors affecting enzyme activity

Overview

How temperature, substrate concentration and pH affect enzyme activity, optimum temperature and pH, the amylase and starch investigation with buffers, iodine and a water bath, its variables, errors and results, and accuracy, precision, repeatability, reproducibility, and random and systematic errors.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Describe the effect of raising the temperature on enzyme activity below the optimum.

   Model answer

   The rate of reaction increases, roughly doubling for every 10 °C rise up to the optimum.

2. 2

   Explain why enzyme activity increases as temperature rises towards the optimum.

   Model answer

   The enzyme and substrate molecules gain kinetic energy and move faster, so they collide more often and more substrate enters active sites each second.

3. 3

   What is meant by the optimum temperature of an enzyme?

   Model answer

   It is the temperature at which the enzyme catalyses its reaction at the fastest rate.

4. 4

   Explain the shape of a graph of enzyme activity against temperature above the optimum.

   Model answer

   The rate falls sharply because increasing numbers of enzyme molecules are denatured, leaving fewer working active sites.

5. 5

   Describe how enzyme activity changes as substrate concentration is increased from zero.

   Model answer

   The rate rises in proportion to substrate concentration at first, then levels off at a maximum.

6. 6

   Explain why increasing substrate concentration eventually stops increasing the rate of reaction.

   Model answer

   Every active site is already occupied, so adding more substrate cannot increase the number of reactions taking place each second.

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