Question

Prelab - Cellular Respiration Name: Answer the following questions and turn them into your TA at the beginning of discussion. 1. Can yeast survive in both aerobic and anaerobic conditions? If not, in which conditions can they survive? 2. Hypothesis Testing: Will yeast produce CO, in aerobic conditions? Will yeast produce CO, in anaerobic conditions? Support your hypotheses. 3. Hypothesis Testing: Will yeast produce ethanol in aerobic conditions? Will yeast produce ethanol in anaerobic conditions? Support your hypotheses. 4. What is the function of fermentation? Why does a cell perform fermentation if it does not produce any ATP energy for the cell? Can human cells perform fermentation? 5. Hypothesis Testing: Will the time it takes to neutralize the 0.1% KOH solution be greater or lesser as exercise intensity increases? Support your hypothesis

Please answer all questions

Answer 1

1. Yeast is a facultative anaerobic organism. i.e. it can survive in both aerobic and anaerobic conditions.

2. Yeast can perform aerobic respiration in the presence of oxygen.
Molecular oxygen is the terminal electron acceptor in aerobic respiration.
Products of aerobic respiration = CO2, and H2O

Yeast can perform anaerobic respiration in the absence of oxygen.
Products of anaerobic respiration = CO2 and Ethanol

3. No
Yeast cannot produce ethanol under aerobic conditions.
This is due to the fact that aerobic respiration is more efficient than anaerobic respiration i.e. aerobic respiration produces ~36 ATP/glucose whereas anaerobic respiration produces 2 ATP/glucose.
So, yeast prefers to grow by aerobic respiration if oxygen is present.

4. Fermentation does not produce ATP or NADH. Instead, it in fact oxidizes 1 NADH molecule per pyruvate.
The function of fermentation is to regenerate NAD+ so that glycolysis can continuously occur under anaerobic conditions.
Humans do perform anaerobic conditions under certain conditions such as strenuous exercise. They produce lactic acid.

5. As the exercise intensity increases, the amount of CO2 produced decreases due to anaerobic respiration. So, the time it takes to neutralize 0.1% KOH solution would be proportional to the intensity of exercise.

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