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Yeast is a single-celled, microscopic fungus that uses sucrose as a food source - VCE - SSCE Biology - Question 1 - 2013 - Paper 1
Question 1
Yeast is a single-celled, microscopic fungus that uses sucrose as a food source. An experiment was carried out to investigate cellular respiration by a particular sp... show full transcript
Worked Solution & Example Answer:Yeast is a single-celled, microscopic fungus that uses sucrose as a food source - VCE - SSCE Biology - Question 1 - 2013 - Paper 1
Step 1
1a. Explain the change in percentage of ethanol and oxygen.
Answer
The increase in the percentage of ethanol from 0% to 4% indicates that ethanol levels rose, which is a product of anaerobic respiration. Concurrently, the decrease in the percentage of oxygen from 21% to 18% reflects that oxygen levels diminished, providing evidence that aerobic respiration was not fully taking place due to the absence of sufficient oxygen. Thus, cellular respiration was not a suitable term to describe the process being observed.
Step 2
1b. Predict and explain the change in carbon dioxide (CO2) levels.
Answer
Prediction: Increase.
Explanation: Carbon dioxide (CO2) is a product of cellular respiration, which includes both aerobic and anaerobic processes. As the yeast metabolizes sucrose, CO2 is produced, especially under anaerobic conditions, leading to an increase in CO2 levels as respiration progresses.