Yeast cells produce alcohol (ethanol) in a process called fermentation - Leaving Cert Biology - Question 8 - 2019
Question 8
Yeast cells produce alcohol (ethanol) in a process called fermentation.
(i) Is oxygen necessary for this process?
(ii) Where in the cell does this process take pla... show full transcript
Worked Solution & Example Answer:Yeast cells produce alcohol (ethanol) in a process called fermentation - Leaving Cert Biology - Question 8 - 2019
Step 1
Is oxygen necessary for this process?
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Answer
No, fermentation is an anaerobic process, meaning it occurs in the absence of oxygen.
Step 2
Where in the cell does this process take place?
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Answer
The process of fermentation occurs in the cytosol or cytoplasm of the yeast cells.
Step 3
Draw a labelled diagram of the apparatus you used.
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Answer
The diagram should illustrate a reaction vessel containing yeast and sugar in an anaerobic condition, with labels indicating key components such as the yeast, sugar solution, and airlock.
Step 4
From which substance did the yeast make the alcohol?
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The yeast made the alcohol primarily from glucose or other named sugars present in the reaction mixture.
Step 5
What is the optimum temperature for this fermentation process?
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The optimum temperature for fermentation is typically in the range of 20°C to 35°C.
Step 6
How did you maintain this temperature at a constant level for the duration of the fermentation?
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I maintained the temperature using a water bath or an incubator to ensure consistent heating throughout the fermentation period.
Step 7
How did you know when the fermentation was finished?
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Fermentation was considered complete when there were no more gas bubbles produced, indicating that there was limited or no further carbon dioxide generation.
Step 8
How did you test for the presence of alcohol?
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To test for the presence of alcohol, I employed the iodometry test using iodine or sodium hypochlorite (or ClO).
Step 9
Give the colour of the positive result of the test.
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The positive result of the test for alcohol showed a yellow coloration.
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