AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Transfer of biomass: Large amounts of glucose are used in respiration.
Glucose is the main respiratory substrate.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 5 of 7
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Glucose is the main respiratory substrate. In aerobic respiration, glucose is broken down in cells using oxygen to release energy for processes such as muscle contraction, active transport and building large molecules. Because so much energy is needed, a large proportion of the glucose produced by photosynthesis or absorbed from food is used in respiration rather than stored as biomass. This helps explain why biomass decreases along a food chain: much of the glucose taken in by an organism is respired, releasing carbon dioxide and water, and only some becomes new biomass.
For example: A cow eats grass containing glucose; most of that glucose is respired to power the cow's life processes, so only a fraction becomes cow biomass available to the next trophic level.
What earns the marks
- Glucose is broken down in respiration to release energy for the organism.
- Aerobic respiration uses oxygen and releases carbon dioxide and water.
- Energy released is used for life processes such as movement, active transport, cell division and maintaining body temperature.
- Because much glucose is respired, less of the ingested or produced glucose becomes new biomass.
- Respiration occurs in all living cells, including producers, consumers and decomposers.
Common mistakes and how to put them right
Saying glucose is used to make energy.
Put it right by stating respiration releases energy from glucose, and energy is not made.
Thinking plants do not respire.
Put it right by stating plants respire continuously as well as photosynthesising in light.
Assuming all glucose eaten becomes biomass.
Put it right by stating a large amount is respired, so only some becomes new biomass.
Exam tips
- Link the idea of glucose use in respiration to the decrease in biomass along a food chain.
- Use the phrase releases energy from glucose rather than makes energy.
- When calculating biomass transfer, remember that respired glucose leaves the organism as carbon dioxide and water, so it is not available to the next trophic level.
Try the lesson
The start of the Transfer of biomass: Large amounts of glucose are used in respiration. lesson, made from checked teaching notes for this specification point.
Have a go first
Which process uses large amounts of glucose to release energy in cells?
Listen
Glucose is the main respiratory substrate. In aerobic respiration, glucose is broken down in cells using oxygen to release energy for processes such as muscle contraction, active transport and building large molecules. Because so much energy is needed, a large proportion of the glucose produced by photosynthesis or absorbed from food is used in respiration rather than stored as biomass. This helps explain why biomass decreases along a food chain: much of the glucose taken in by an organism is respired, releasing carbon dioxide and water, and only some becomes new biomass. For example, a cow eats grass containing glucose; most of that glucose is respired to power the cow's life processes, so only a fraction becomes cow biomass available to the next trophic level. A strong answer earns marks for these points. Glucose is broken down in respiration to release energy for the organism. Aerobic respiration uses oxygen and releases carbon dioxide and water. Energy released is used for life processes such as movement, active transport, cell division and maintaining body temperature. Because much glucose is respired, less of the ingested or produced glucose becomes new biomass. A common slip: Saying glucose is used to make energy. Instead, stating respiration releases energy from glucose, and energy is not made. Exam tip: Link the idea of glucose use in respiration to the decrease in biomass along a food chain.
Key words
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Respiration as energy release
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Glucose as respiratory substrate
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Energy loss in food chains
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Biomass transfer between trophic levels
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See every definition
- Respiration as energy release
- Glucose is broken down in cells using oxygen to release energy for processes such as muscle contraction, active transport and building large molecules.
- Glucose as respiratory substrate
- Glucose is the main respiratory substrate, and a large proportion of the glucose produced by photosynthesis or absorbed from food is used in respiration rather than stored as biomass.
- Energy loss in food chains
- Much of the glucose taken in by an organism is respired, releasing carbon dioxide and water, which helps explain why biomass and energy decrease between trophic levels.
- Biomass transfer between trophic levels
- Only a fraction of the glucose taken in becomes new biomass available to the next trophic level, because most of it is respired to power the organism's life processes.
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