Respiration in yeast

Question 1

What reagent can be used to indicate the rate of respiration? How?

Answer 1

A redox indicator.

It oxidizes reduced NAD and FAD, so it itself is reduced, causing a change in color.

Question 2

What is the dependent variable of this practical?

Answer 2

The rate of respiration measured by the time taken for the redox indicator to change color.

Question 3

Outline the procedure to investigate the effect of temperature on the rate of respiration.

Answer 3

1. Set up the first water bath at 35°C
2. Use pipette to place 10cm3 of the yeast suspension into one test tube and 1cm3 of redox indicator into a different test tube
3. Place both test tubes into the water bath, leave them for 5 minutes
4. Pour redox indicator into the test tube containing the yeast, stir it and start the stop watch.
5. Repeat steps 1-4 with the remaining temperatures

Question 4

Why are the test tubes left in the water bath for 5 minutes before mixing?

Answer 4

To allow the solutions to reach the temperature of the water bath.W

Question 5

What are the controlled variables of this practical?

Answer 5

Volume of yeast culture
Volume of redox indicator

Question 6

State the hazards and safety precautions of this practical.

Answer 6

Redox indicator is a potential irritant, avoid contact with skin.