RP09: Respiration In Single Celled Organisms

Question 1

What is function of methylene blue in this practical

Answer 1

It’s a redox dye and acts as an alternate electron acceptor of the electrons transferred during ATP synthesis

It turns from blue to colourless, indicating the end point

Question 2

Outline procedure to investigate effect of temp on respiration rate of yeast

Answer 2

1. Set up a water bath at 35°C.
2. Add equal volumes of the yeast and glucose solution to three test tubes.
   Place test tubes in the water bath and leave them to equilibrate for 10 minutes.
3. Add 2 cm’ of methylene blue to the test tubes and start the timer. Shake for
   10 seconds and place test tube back in water bath. Record how long it takes for the methylene blue to turn colourless for each test tube.
4. Repeat the experiment using temperatures of 40°C, 50°C, 60°C and 70°C.

Question 3

How are results used to calculate respiration rate at each temp

Answer 3

Rate =

1 / time taken for methylene blue to decolourise

Question 4

Why does the yeast solution need to be buffered

Answer 4

To maintain a constant pH so that the enzymes are functioning at their optimum pH

Question 5

What is effect of temp on respiration rate

Answer 5

As temp increase, respiration rate increases to an optimum. This because enzyme activity rate increases

Beyond optimum, enzyme activity decreases as enzymes denature with high temp