AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Respiration in cells can take place aerobically (using oxygen) or…
Full specification wording
Aerobic and anaerobic respiration: Respiration in cells can take place aerobically (using oxygen) or anaerobically (without oxygen), to transfer energy.
Cells can transfer energy from glucose by two pathways.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 3 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Cells can transfer energy from glucose by two pathways. Aerobic respiration takes place with oxygen, occurs mainly in mitochondria, and completely breaks down glucose to carbon dioxide and water, transferring a relatively large amount of energy per glucose molecule. Anaerobic respiration takes place without oxygen, occurs in the cytoplasm, and partially breaks down glucose. In animals and some other organisms, glucose is converted to lactic acid, which can cause muscle fatigue and an oxygen debt that must be repaid after exercise. In plants and yeast, anaerobic respiration produces ethanol and carbon dioxide; in yeast this is fermentation, used in brewing and bread-making. Both pathways transfer energy, but anaerobic respiration transfers less energy per glucose molecule because glucose is not fully oxidised.
What earns the marks
- Aerobic respiration requires oxygen and occurs mainly in mitochondria.
- Aerobic respiration completely oxidises glucose to carbon dioxide and water, transferring a relatively large amount of energy.
- Anaerobic respiration occurs without oxygen and takes place in the cytoplasm.
- In animals, anaerobic respiration converts glucose to lactic acid and transfers less energy per glucose molecule.
- In plants and yeast, anaerobic respiration produces ethanol and carbon dioxide.
- Anaerobic respiration in muscle leads to oxygen debt, which is repaid by continued fast breathing and heart rate after exercise.
Common mistakes and how to put them right
Writing that anaerobic respiration produces carbon dioxide and water in human muscle.
Put it right: Human muscle produces lactic acid, while plants and yeast produce ethanol and carbon dioxide.
Stating that anaerobic respiration releases the same energy as aerobic respiration.
Put it right: It transfers less energy per glucose molecule because glucose is only partially broken down.
Placing anaerobic respiration in the mitochondria.
Put it right: It occurs in the cytoplasm, whereas aerobic respiration occurs mainly in mitochondria.
Exam tips
- Compare the two pathways using oxygen requirement, products, location and relative energy transferred.
- Use the correct products for the named organism: lactic acid in animals, ethanol and carbon dioxide in plants and yeast.
- When explaining oxygen debt, link lactic acid breakdown to the need for continued oxygen supply after exercise.
Try the lesson
The start of the Aerobic and anaerobic respiration: Respiration in cells can take place aerobically (using oxygen) or anaerobically (without oxygen), to transfer energy. lesson, made from checked teaching notes for this specification point.
Have a go first
Which gas is used by cells when respiration takes place aerobically?
Listen
Cells can transfer energy from glucose by two pathways. Aerobic respiration takes place with oxygen, occurs mainly in mitochondria, and completely breaks down glucose to carbon dioxide and water, transferring a relatively large amount of energy per glucose molecule. Anaerobic respiration takes place without oxygen, occurs in the cytoplasm, and partially breaks down glucose. In animals and some other organisms, glucose is converted to lactic acid, which can cause muscle fatigue and an oxygen debt that must be repaid after exercise. In plants and yeast, anaerobic respiration produces ethanol and carbon dioxide; in yeast this is fermentation, used in brewing and bread-making. Both pathways transfer energy, but anaerobic respiration transfers less energy per glucose molecule because glucose is not fully oxidised. A strong answer earns marks for these points. Aerobic respiration requires oxygen and occurs mainly in mitochondria. Aerobic respiration completely oxidises glucose to carbon dioxide and water, transferring a relatively large amount of energy. Anaerobic respiration occurs without oxygen and takes place in the cytoplasm. In animals, anaerobic respiration converts glucose to lactic acid and transfers less energy per glucose molecule. A common slip: Writing that anaerobic respiration produces carbon dioxide and water in human muscle. Instead, human muscle produces lactic acid, while plants and yeast produce ethanol and carbon dioxide. Exam tip: Compare the two pathways using oxygen requirement, products, location and relative energy transferred.
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Key words
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Aerobic respiration
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Anaerobic respiration
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Oxygen debt
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Fermentation
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See every definition
- Aerobic respiration
- Respiration that takes place using oxygen, occurs mainly in mitochondria, and completely breaks down glucose to carbon dioxide and water, transferring a relatively large amount of energy per glucose molecule.
- Anaerobic respiration
- Respiration that takes place without oxygen, occurs in the cytoplasm, and partially breaks down glucose, transferring less energy per glucose molecule because glucose is not fully oxidised.
- Oxygen debt
- Produced when anaerobic respiration in muscle converts glucose to lactic acid, and it must be repaid after exercise by continued fast breathing and heart rate.
- Fermentation
- Anaerobic respiration in yeast that produces ethanol and carbon dioxide, used in brewing and bread-making.
Label the diagram
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