AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
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 routes.
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Cells can transfer energy from glucose by two routes. Aerobic respiration uses oxygen and occurs mainly in mitochondria; it completely oxidises glucose, transferring a large amount of energy and producing carbon dioxide and water. Its word equation is glucose + oxygen → carbon dioxide + water. Anaerobic respiration occurs without oxygen in the cytoplasm; glucose is only partially broken down, so less energy is transferred. In animals and some bacteria it produces lactic acid: glucose → lactic acid. In plants and yeast it produces ethanol and carbon dioxide: glucose → ethanol + carbon dioxide. Anaerobic respiration in muscles occurs during vigorous exercise when oxygen supply is limited, and yeast uses it in fermentation.
What earns the marks
- Aerobic respiration requires oxygen and transfers more energy per glucose molecule than anaerobic respiration.
- Anaerobic respiration takes place without oxygen and transfers less energy because glucose is not fully broken down.
- Aerobic respiration produces carbon dioxide and water, whereas anaerobic respiration in animals produces lactic acid.
- Anaerobic respiration in plants and yeast produces ethanol and carbon dioxide.
- Aerobic respiration occurs mainly in mitochondria, while anaerobic respiration occurs in the cytoplasm.
Common mistakes and how to put them right
Writing that anaerobic respiration produces carbon dioxide and water in human muscle.
Put it right by stating it produces lactic acid.
Claiming anaerobic respiration transfers the same energy as aerobic respiration.
Put it right by stating that less energy is transferred because glucose is partially broken down.
Stating that anaerobic respiration occurs only in muscles.
Put it right by noting that yeast and plant cells also respire anaerobically.
Exam tips
- Learn both word equations and be ready to compare the energy transferred in each pathway.
- When comparing aerobic and anaerobic respiration, structure your answer around oxygen requirement, products and energy transferred.
- Use 'partially broken down' for anaerobic respiration and 'completely oxidised' for aerobic respiration to show precise understanding.
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 during aerobic respiration?
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Key words
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Aerobic respiration
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Anaerobic respiration
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Lactic acid
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Ethanol and carbon dioxide
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See every definition
- Aerobic respiration
- Respiration that uses oxygen, occurs mainly in mitochondria, completely oxidises glucose and transfers a large amount of energy.
- Anaerobic respiration
- Respiration that occurs without oxygen in the cytoplasm, where glucose is only partially broken down so less energy is transferred.
- Lactic acid
- The product of anaerobic respiration in animals and some bacteria, made from glucose.
- Ethanol and carbon dioxide
- The products of anaerobic respiration in plants and yeast, made from glucose.
Label the diagram
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