1:5:6 Demonstrating Anaerobic Respiration in Yeast

Question 1

Apparatus

Answer 1

Two test tubes, beaker with straw in it to filter CO2 through to beaker 2

Oil layer, Yeast in Glucose solution, Lime Water

Question 2

Why is oil placed on top of the glucose

Answer 2

To prevent oxygen entering the solution

Question 3

Explain the stages of methods and the reasons for them.

Answer 3

1. Boiling glucose solution - Removes dissolved oxygen/sterilises it.
2. Yeast cells are added when the solution cools - Prevents yeast from being killed.
3. Layer of oil is added - Prevents oxygen entering solution.

Question 4

What would you observe if the experiment is done correctly?

Answer 4

The Limewater turns milky in the presence of carbon dioxide.

The contents of the boiling tube:

More yeast present
Less glucose present
Bubbles of carbon dioxide gas
Heat given out
Contains alcohol