Respiration

Question 1

What are the 4 stages of respiration?

Answer 1

Glycolysis, link reaction, krebs cycle or calvin cycle, electron transport chain or chemiosmosis.

Question 2

How many atps does respiration make?

Answer 2

38

Question 3

What is the function of the methylene blue in this practical?

Answer 3

It is a redox dye and acts as an alternate electron acceptor of the electrons during ATP synthesis. It turns from blue to colourless, indicat8g the end point.

Question 4

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

Answer 4

1. Set up a water bath at 35c
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 10mins
3. Add 2cm of methylene blues 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 40,50,60,and 70c

Question 5

How are the results used to calculate the rate of respiration at each temperature?

Answer 5

Rate=1/ time taken for methylene blue to decolourise

Question 6

Why does the yeast solution need to be buffered?

Answer 6

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

Question 7

What is the effect of temperature on the rate of respiration?

Answer 7

As temperature increases, the rate of respiration increases to an optimum. This is because the rate of enzyme activity increases. Beyond the optimum, enzyme activity decreases as enzymes denature with high temperature.