Explain how pH values above or below the optimum affect enzyme structure.

They alter the ionisation of amino acid R groups, disrupting ionic bonds and hydrogen bonds that maintain the tertiary structure of the active site.

Explain why increasing temperature below the optimum increases the rate of an enzyme-controlled reaction.

Molecules have more kinetic energy, leading to more frequent and energetic collisions between enzyme and substrate.

Why does the rate of an enzyme-controlled reaction decrease above the optimum temperature?

Increased vibration of the enzyme breaks hydrogen bonds and other bonds maintaining the tertiary structure, denaturing the enzyme.

AQA A-Level Biology 7402

Biological Molecules

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Biological Molecules

pH, temperature, initial rates and measurement uncertainty

3 things to know
Papers 1 and 3

Overview

Recall questions on how pH and temperature affect enzyme activity and denaturation, finding initial rate with a tangent, and accuracy, precision, uncertainty, percentage error and controls in enzyme investigations.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is meant by the optimum pH of an enzyme?

Key term

What happens to an enzyme at extreme pH values?

Key term

What is the optimum temperature of an enzyme?

Questions from this subtopic

Each one with the model answer underneath.

1
What is meant by the optimum pH of an enzyme?
Model answer
The pH at which the rate of reaction is maximum.
2
Explain how pH values above or below the optimum affect enzyme structure.
Model answer
They alter the ionisation of amino acid R groups, disrupting ionic bonds and hydrogen bonds that maintain the tertiary structure of the active site.
3
What happens to an enzyme at extreme pH values?
Model answer
Denaturation occurs, permanently altering the shape of the active site so the substrate can no longer bind.
4
What is the optimum temperature of an enzyme?
Model answer
The temperature at which the rate of reaction is maximum.
5
Explain why increasing temperature below the optimum increases the rate of an enzyme-controlled reaction.
Model answer
Molecules have more kinetic energy, leading to more frequent and energetic collisions between enzyme and substrate.
6
Why does the rate of an enzyme-controlled reaction decrease above the optimum temperature?
Model answer
Increased vibration of the enzyme breaks hydrogen bonds and other bonds maintaining the tertiary structure, denaturing the enzyme.

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Biological Molecules

Cells

Organisms Exchange Substances with Their Environment

Genetic Information, Variation and Relationships Between Organisms

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phosphodiesterglycosidicpeptide

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Genotype means the genetic constitution of an organism.

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