Question

1. in a laboratory, a 15% glucose solution is fermented at 10°c and at a ph of 4.5. according to the data above, which two factors could be adjusted to increase the rate of fermentation?

a decrease the initial percentage of glucose
b increase the initial percentage of glucose
c decrease the temperature
d increase the temperature
e decrease the ph
f increase the ph

1. in the presence of oxygen, saccharomyces cerevisiae can undergo either fermentation or aerobic respiration depending on the amount of glucose present. which of the following would you expect to increase when aerobic respiration is taking place?

a the amount of ethanol produced
b the amount of carbon dioxide produced
c the amount of glucose produced
d the amount of oxygen produced

Explanation:

Question 34

To increase fermentation rate, factors like substrate (glucose) concentration, temperature (within optimal range), and pH (optimal) matter. Increasing initial glucose (substrate) and increasing temperature (if 10°C is below optimal) can boost rate. Decreasing glucose or temperature, or wrong pH changes (decreasing/increasing from 4.5 if it's optimal) won't. So B (increase initial glucose) and D (increase temperature) are correct, but since we pick two, but the options—wait, the question says "which two factors". Wait, the options are A to F. Let's analyze:

• A: Decrease glucose (substrate) → slows rate.
• B: Increase glucose (substrate) → increases rate (more substrate for enzymes).
• C: Decrease temperature (10°C is low; enzymes have optimal temp, increasing temp (D) is better, decreasing (C) slows).
• D: Increase temperature (if 10°C is below optimal, increasing temp increases enzyme activity).
• E: Decrease pH (if 4.5 is optimal, decreasing pH is bad).
• F: Increase pH (if 4.5 is optimal, increasing pH is bad).

So the two factors are B (increase the initial percentage of glucose) and D (increase the temperature). But the question is multiple-choice for two factors. Assuming the options are to pick two, but the problem's options are A - F. Wait, maybe the correct two are B and D. But let's check again. Fermentation rate depends on substrate concentration, temperature, pH. So increasing glucose (B) and increasing temperature (D) are correct.

Saccharomyces cerevisiae (yeast) in aerobic respiration:

• Fermentation (anaerobic) produces ethanol (A) and CO₂.
• Aerobic respiration: uses glucose, produces CO₂, H₂O, and more ATP. Ethanol is from fermentation (anaerobic), so aerobic respiration decreases ethanol production (A: ethanol decreases).
• CO₂: aerobic respiration of glucose produces more CO₂ per glucose than fermentation? Wait, no—1 glucose in aerobic: 6 CO₂; in fermentation: 2 CO₂. Wait, but the question is "which would you expect to increase when aerobic respiration is taking place" (with glucose present). Wait, aerobic respiration uses glucose, so:
• A: Ethanol (fermentation product) → aerobic respiration reduces fermentation, so ethanol decreases.
• B: CO₂: aerobic respiration of glucose produces 6 CO₂ per glucose, while fermentation produces 2. So if aerobic starts, CO₂ production increases (since more efficient, but wait, no—if glucose is present, aerobic respiration would use glucose, producing more CO₂ than fermentation? Wait, no: fermentation: 1 glucose → 2 ethanol + 2 CO₂. Aerobic: 1 glucose → 6 CO₂. So if aerobic respiration is taking place (instead of fermentation), with glucose present, CO₂ production (B) increases.
• C: Glucose produced? No, yeast uses glucose, doesn't produce it.
• D: Oxygen produced? No, yeast consumes O₂ in aerobic, doesn't produce it.

Wait, the question is "which of the following would you expect to increase when aerobic respiration is taking place" (with glucose present). So:

• Aerobic respiration: consumes glucose, produces CO₂ (more than fermentation), consumes O₂, produces no ethanol (fermentation product). So CO₂ (B) increases. Ethanol (A) decreases. Glucose (C) decreases (consumed). Oxygen (D) decreases (consumed). So the answer is B (the amount of carbon dioxide produced).

Answer:

B. increase the initial percentage of glucose, D. increase the temperature

Question 35