8. (a) (i) What gas must be absent for anaerobic respiration to occur?
(ii) Does anaerobic respiration release more or less energy than aerobic respiration?
(b) Answer the following questions in relation to the production of alcohol by yeast - Leaving Cert Biology - Question 8 - 2017
Question 8
8. (a) (i) What gas must be absent for anaerobic respiration to occur?
(ii) Does anaerobic respiration release more or less energy than aerobic respiration?
(b) ... show full transcript
Worked Solution & Example Answer:8. (a) (i) What gas must be absent for anaerobic respiration to occur?
(ii) Does anaerobic respiration release more or less energy than aerobic respiration?
(b) Answer the following questions in relation to the production of alcohol by yeast - Leaving Cert Biology - Question 8 - 2017
Step 1
(i) What gas must be absent for anaerobic respiration to occur?
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Answer
The gas that must be absent for anaerobic respiration to occur is oxygen.
Step 2
(ii) Does anaerobic respiration release more or less energy than aerobic respiration?
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Answer
Anaerobic respiration releases less energy than aerobic respiration.
Step 3
1. To which flask was the yeast added?
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Answer
The yeast was added to flask A.
Step 4
2. Give a reason for your choice.
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Answer
The yeast was added to flask A because it produces bubbles (indicating CO₂ production during fermentation).
Step 5
(ii) What is the purpose of the other flask?
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The purpose of the other flask is to serve as a control.
Step 6
(iii) Name the two substances in the original solution in the flasks.
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Glucose or sugar.
Water.
Step 7
(iv) What is the purpose of the water bath?
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The purpose of the water bath is to keep the temperature constant during the fermentation process.
Step 8
(v) What is the purpose of a fermentation lock?
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Answer
The purpose of a fermentation lock is to keep oxygen out or to avoid contamination.
Step 9
(vi) Say what test you performed to show the presence of alcohol and say what colour indicated a positive result.
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Answer
The test performed to show the presence of alcohol is the iodiform (or iodine) test. The positive colour observed is yellow (or green if dichromate is used).
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