Edexcel IAL Biology 2.8 Core Practical 4 enzyme reaction rate

Use the earliest linear data or a correctly placed tangent, retain concentration and time units and explain each trend through collisions, complexes or denaturation.

Exam points

Calculate initial rate from early data or a tangent with correct compound units.
Explain substrate or enzyme concentration curves through collisions and active sites.
Interpret pH and temperature data through optimum conditions and denaturation.

[Maximum number: 7]

The enzyme invertase breaks down sucrose into its two component monosaccharides.

(a)

Suggest why the temperature was kept at 25^ C.

[ 2 ]

An answer that makes reference to the following points:

- temperature affects \{action/ reaction rate/ number of (S and E) collisions\} of enzyme (1)

- $\left(25^{\circ} \mathrm{C}\right)$ \{may be / is\} optimum (for invertase) / gives rate which is not too fast or slow / (1)

ACCEPT so that only pH affects rate

ACCEPT above $25^{\circ} \mathrm{C}$ denatures enzyme

(2)

(b)

Explain why the initial rate of this reaction was determined.

[ 2 ]

(c)

Invertase is used in the food industry. Scientists wanted to increase the efficiency of the enzyme to save time and money.

One way is to immobilise the enzyme by binding it to a surface. This stops the enzyme molecules from moving.

The effect of temperature on immobilised invertase and non-immobilised invertase was investigated. The results are shown in the graph.

Figure for Question (c) — Edexcel A-Level Biology AS

Compare and contrast the effect of temperature on these two forms of invertase.

[ 3 ]

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2.8—Core Practical 4 - enzyme-catalysed reaction rate question 1

Question (a)

Question (b)

Question (c)