Cambridge IGCSE · Sciences - Co-ordinated (Double) (0654)

Enzymes: Practice Questions

5 multiple-choice questions marked as you go, and 3 written questions with worked solutions. All on Enzymes.

8 questions17 marksFree, no account

Question 1

1 mark

What is the term used to describe the part of an enzyme molecule into which a substrate fits?

Question 2

1 mark

A student investigates the effect of pH on the activity of a protease enzyme. The enzyme is most active at pH \(2.0\). When the pH is increased to pH \(12.0\), the reaction stops completely.
Which statement correctly explains this observation?

Question 3

1 mark

A student set up two test tubes, P and Q, each containing a fixed concentration of amylase and starch solution.
Test tube P was maintained at \(10^\circ C\).
Test tube Q was maintained at \(60^\circ C\).
The rate of starch breakdown was found to be very low in both tubes. Which statement correctly explains the molecular basis for these results?<\/p>

Question 4

1 mark

Enzymes are described as proteins that function as biological catalysts. Based on their chemical nature, which set of elements is always present in any enzyme molecule?

Question 5

1 mark

The graph of an enzyme's activity against pH shows a bell-shaped curve. What is the molecular explanation for the low activity at pH values far away from the optimum?

Question 6

3 marks

Explain why the rate of an enzyme-controlled reaction decreases rapidly when the temperature is increased significantly above the optimum temperature.

Write your answer out first, then check it against the worked solution.

Question 7

4 marks

Enzymes play an essential role in biological systems.
(a) Define the term enzyme.
(b) State the type of biological molecule from which all enzymes are made.
(c) State two environmental conditions that can affect the activity of an enzyme.

Write your answer out first, then check it against the worked solution.

Question 8

5 marks

The provided graph illustrates the effect of temperature on the rate of a reaction catalyzed by a human digestive enzyme.
(a) Explain the increase in the rate of reaction as the temperature rises from \(10^\circ\text{C}\) to \(37^\circ\text{C}\) in terms of kinetic energy and the frequency of effective collisions.
(b) Above \(45^\circ\text{C}\), the rate of reaction decreases rapidly until it stops. Explain this observation by referring to the active site and the process of denaturation.
(c) Identify one other factor, besides temperature, that can similarly cause an enzyme to denature if it deviates significantly from the optimum.

Write your answer out first, then check it against the worked solution.

* The content provided by thinka is generated by AI and may not always be accurate or up-to-date. Please use it as a supplementary resource and verify with official materials.

You've seen the model answer. Now get yours marked.

This page can show you how a good answer looks. It cannot tell you what your answer was missing. thinka marks your written work against the real mark scheme in about 15 seconds.

Get My Answers Marked Back to the notes

Want more questions like these? Get a fresh set on this topic, graded as you go.

Practice More