7. (a) Yeast cells produce ethanol (alcohol) in a process called fermentation - Leaving Cert Biology - Question 7 - 2004
Question 7
7.
(a) Yeast cells produce ethanol (alcohol) in a process called fermentation.
Is this process affected by temperature?
Explain your answer.
(b) Answer the... show full transcript
Worked Solution & Example Answer:7. (a) Yeast cells produce ethanol (alcohol) in a process called fermentation - Leaving Cert Biology - Question 7 - 2004
Step 1
Is this process affected by temperature?
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Answer
Yes, the process of fermentation is affected by temperature because the rate of enzyme reactions, which drive the fermentation process, changes with temperature. Enzymes typically have an optimal temperature range where they function most efficiently. At lower temperatures, the reaction rate decreases, while at higher temperatures, enzyme denaturation can occur, leading to a halt in fermentation.
Step 2
Draw a labelled diagram of the apparatus you used.
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Answer
The diagram should include essential components such as a fermentation vessel containing sugar or starch, an airlock to prevent oxygen from entering, and a collection tube to capture carbon dioxide. Ensure that the diagram indicates anaerobic conditions, and label at least two components accurately.
Step 3
Name a substance that yeast can use to make ethanol.
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Yeast can use glucose as a substance to make ethanol during the fermentation process.
Step 4
What substance, other than ethanol, is produced during fermentation?
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Carbon dioxide is also produced during the fermentation process, alongside ethanol.
Step 5
Describe the control that you used in this experiment.
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The control in this experiment may involve a setup where yeast is absent or dead, serving as a comparison to observe whether fermentation occurs in the active yeast setup.
Step 6
Explain the purpose of a control in a scientific experiment.
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The purpose of a control in a scientific experiment is to establish a baseline for comparison. It allows the experimenter to determine if any observed effect is due to the experimental variable or if it occurred by chance.
Step 7
How did you know when the fermentation was finished?
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Fermentation is considered finished when no more gas (carbon dioxide) is being produced, which can be observed by the cessation of bubbles in the apparatus.
Step 8
Why were solutions of potassium iodide and sodium hypochlorite added to the reaction vessels after a certain period of time?
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Potassium iodide and sodium hypochlorite can be added to test for the presence of ethanol. Potassium iodide forms a complex with ethanol, while sodium hypochlorite helps to oxidize any remaining ethanol to verify fermentation completion.
Step 9
Name a substance produced during aerobic respiration that is not produced during fermentation.
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Water is a substance produced during aerobic respiration that is not produced during fermentation.
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