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CAIE IGCSE Biology 5.1 Enzymes Questions

Practise defining catalysts and enzymes, explaining active-site specificity, and interpreting temperature or pH activity data.

Syllabus
2026–2028
Course
Biology 0610

Exam points

  • Define catalysts and enzymes as substances that increase reaction rate without being used up, and state that enzymes are proteins involved in metabolic reactions.
  • Explain enzyme action using substrate, active site, enzyme-substrate complex and products, including complementary shape and specificity.
  • Interpret temperature and pH activity data by identifying optima, explaining collision rates below the optimum and active-site denaturation above or away from it.

Covered syllabus points

5.1.1—Catalyst as a substance that increases5.1.2—Enzymes as proteins that are involved5.1.3—Why enzymes are important in all5.1.4—Enzyme action with reference5.1.5—Temperature, pH and enzyme activity5.1.6—Enzyme action with reference5.1.7—Specificity of enzymes in terms5.1.8—Effect of changes in temperature on5.1.9—Effect of changes in pH on enzyme

Question 1

[Maximum number: 9]

Enzymes are biological catalysts.

Question (a)

(a)

Describe what is meant by the term catalyst.

[ 2 ]

Question (b)

(b)

A student investigated the effect of temperature on enzyme activity.

A starch suspension was kept at 0∘C0^{\circ} \mathrm{C}.
Amylase solution was added to the starch suspension.
Samples of the starch and amylase mixture were tested with iodine solution at 1 -minute intervals for 15 minutes.

The student recorded the time at which the starch and amylase mixture stopped turning a blue-black colour.

The student repeated this investigation at different temperatures.
Table 3.1 shows the results.

Table 3.1

Table 3.1

[ 6 ]

Question (i)

(i)

Explain the results between 0∘C0^{\circ}\mathrm{C} and 40∘C40^{\circ}\mathrm{C} in Table 3.1.

[ 6 ]

Question (c)

(c)

State one factor, other than temperature, that affects enzyme action.

[ 1 ]

Question 2

[Maximum number: 1]

In addition to sucrose, amino acids are also transported in plants.

State the name of the group of molecules that are made of proteins and act as catalysts.

Question 3

[Maximum number: 1]

Which statement is correct?

A

The active site of an enzyme has the same shape as the substrate.

B

The active site is not affected by changes in temperature.

C

The shape of the active site of an enzyme is complementary to its substrate.

D

The substrate and product combine at the active site.

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