Exercises: Investigating Enzymes and Industrial Uses

Name four factors that affect the rate of an enzyme-catalysed reaction.

Define an immobilised enzyme and name one method of immobilising enzymes.

State what is meant by the optimum pH of an enzyme and give one example of an enzyme and its optimum pH.

The following results show the volume of product formed by an enzyme in 2 minutes at different temperatures:

1. a) Calculate the rate of reaction at 30 °C in mL per minute.

1. b) Estimate the optimum temperature and explain the shape of the graph from 40 °C to 60 °C.

1. c) Explain why the rate increases from 10 °C to 40 °C.

Lactase is immobilised in alginate beads and used to produce lactose-free milk in a dairy in Co. Cork.

1. a) Describe how the milk is passed over the beads in a column.

1. b) Give two advantages of using immobilised lactase instead of free lactase.

1. c) Explain why lactose-free milk tastes sweeter than ordinary milk.

A student investigates the effect of pH on catalase activity using hydrogen peroxide and liver extract, measuring the height of the foam produced.

1. a) State the independent and dependent variables.

1. b) Explain how a range of pH values would be obtained.

1. c) Explain why a boiled liver extract should be used as a control.

A student investigates the effect of substrate concentration on the rate of an enzyme-catalysed reaction. The rate rises steeply at low concentration, then levels off at high concentration.

1. a) Explain the shape of the graph at low and at high substrate concentration.

1. b) State what happens to the rate at high concentration if the enzyme concentration is doubled, and explain why.

1. c) Explain how a competitive inhibitor would change the graph and how this can be overcome.

An industry wishes to use an enzyme in a continuous process to produce a product, comparing free enzyme with enzyme immobilised on beads.

1. a) Evaluate the two methods in terms of cost, reuse, product purity and stability.

1. b) Explain why immobilised enzymes are often more tolerant of changes in temperature and pH.

1. c) Suggest one disadvantage of immobilisation, with reasoning.

A student's investigation of amylase gives these data for starch remaining after 5 minutes at different pH values:

1. a) Identify the optimum pH and justify your answer.

1. b) Explain, in terms of enzyme structure, why activity is reduced at pH 3 and pH 11.

1. c) Describe how the student could improve the reliability and precision of this investigation, and how the starch remaining could be measured.