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Notre Dame Catholic Sixth Form College - LeedsLeeds

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Figure 1: The production of yeast

Title: The effect of temperature on the rate of respiration in yeast.

AN INVESTIGATION OF THE EFFECT OF

TEMPERATURE ON RESPIRATION IN YEAST

Aim: To investigate the effect of temperature on the rate of respiration in yeast with the use

of a redox indicator.

Variables

Dependent – The time, measured in seconds, taken for the mixture to turn colourless

Independent – Temperature, measured in degree Celsius.

Control variables:

 2cm 3 of the yeast and glucose mixture

 2cm 3 methylene blue

Introduction

• Yeast and Temperature

Yeasts, known scientifically as saccharomyces cerevisiae, are unicellular fungi and needs

energy for its living and growth which gets from respiration. Yeast is crucial in wine-making,

baking and brewing.

Yeast respires because it forms a reaction with glucose; enzymes inside the yeast’s cells

catalyse this reaction. This is because of the successful collisions between the substrates and

the enzyme when heated up. The optimum temperature for enzymes in this reaction is 35 –

40. Below this temperature they work less efficiently and above this temperature the

enzymes denature as there is more kinetic energy which breaks the bonds leading to the

active site changing shape. Therefore, enzyme-substrate complexes will not be formed. [2]

Figure 2: Temperature affecting the enzyme activity.

• Respiration