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 pl... 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 does not require oxygen.
Step 2
Where in the cell does this process take place?
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Answer
Fermentation takes place in the cytoplasm of the yeast cells.
Step 3
Draw a labelled diagram of the apparatus you used.
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A labelled diagram should include a reaction vessel with a liquid surface, an airlock, and the contents such as yeast and sugar.
Step 4
From which substance did the yeast make the alcohol?
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The yeast made the alcohol from glucose or other sugars, such as sucrose.
Step 5
What is the optimum temperature for this fermentation process?
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The optimum temperature for fermentation is usually between 20°C and 35°C.
Step 6
How did you maintain this temperature at a constant level for the duration of the fermentation?
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You can maintain the temperature using a water bath or an incubator set to the desired temperature.
Step 7
How did you know when the fermentation was finished?
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Fermentation is finished when no more gas, specifically carbon dioxide, is produced, or there are no bubbles forming.
Step 8
How did you test for the presence of alcohol?
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The presence of alcohol can be tested using the iodform test, which involves adding potassium iodide and sodium hypochlorite.
Step 9
Give the colour of the positive result of the test.
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The positive result of the test for alcohol yields a yellow colour.
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