AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Metabolism is the sum of all the reactions in a cell or the body.
Full specification wording
Metabolism: Metabolism is the sum of all the reactions in a cell or the body.
Metabolism is not a single process but the total of every chemical reaction occurring in a cell or organism.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 2 of 4
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Metabolism is not a single process but the total of every chemical reaction occurring in a cell or organism. These reactions fall into two broad groups. Synthesis reactions build larger molecules from smaller ones, such as joining glucose to form glycogen or joining amino acids to form proteins. Breakdown reactions split larger molecules into smaller ones, such as breaking down glucose during respiration or breaking down lipids into fatty acids and glycerol. Many metabolic reactions are controlled by enzymes, and they occur at different rates in different cells depending on the cell's role. The idea of metabolism links respiration, digestion, growth, repair and the synthesis of storage molecules, and it helps explain why organisms need a constant supply of energy and raw materials.
What earns the marks
- Metabolism is the sum total of all chemical reactions in a cell or the body.
- Examples include respiration, the formation of glycogen from glucose, and the formation of proteins from amino acids.
- Many metabolic reactions are controlled by enzymes.
- Metabolic activity varies between cells and organisms depending on their functions and energy demands.
Common mistakes and how to put them right
Defining metabolism as only breakdown or only synthesis.
Put it right by stating that it includes both types of reaction.
Confusing metabolism with respiration.
Put it right by explaining that respiration is one important metabolic reaction, but metabolism includes many other reactions too.
Thinking metabolism occurs only in the liver.
Put it right by stating that all cells carry out metabolic reactions, although the liver has many roles.
Exam tips
- Use the phrase 'sum of all reactions' in your definition, then give one synthesis and one breakdown example.
- When asked about a specific process, state whether it is synthesis or breakdown and name the molecules involved.
- Link metabolism to enzyme action by noting that enzymes control the rate of metabolic reactions.
Try the lesson
The start of the Metabolism: Metabolism is the sum of all the reactions in a cell or the body. lesson, made from checked teaching notes for this specification point.
Have a go first
What name is given to the sum of all the reactions in a cell or the body?
Listen
Metabolism is not a single process but the total of every chemical reaction occurring in a cell or organism. These reactions fall into two broad groups. Synthesis reactions build larger molecules from smaller ones, such as joining glucose to form glycogen or joining amino acids to form proteins. Breakdown reactions split larger molecules into smaller ones, such as breaking down glucose during respiration or breaking down lipids into fatty acids and glycerol. Many metabolic reactions are controlled by enzymes, and they occur at different rates in different cells depending on the cell's role. The idea of metabolism links respiration, digestion, growth, repair and the synthesis of storage molecules, and it helps explain why organisms need a constant supply of energy and raw materials. A strong answer earns marks for these points. Metabolism is the sum total of all chemical reactions in a cell or the body. Examples include respiration, the formation of glycogen from glucose, and the formation of proteins from amino acids. Many metabolic reactions are controlled by enzymes. Metabolic activity varies between cells and organisms depending on their functions and energy demands. A common slip: Defining metabolism as only breakdown or only synthesis. Instead, stating that it includes both types of reaction. Exam tip: Use the phrase 'sum of all reactions' in your definition, then give one synthesis and one breakdown example.
See it
Key words
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Metabolism
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Synthesis reactions
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Breakdown reactions
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See every definition
- Metabolism
- The sum of all the reactions in a cell or the body.
- Synthesis reactions
- Reactions that build larger molecules from smaller ones.
- Breakdown reactions
- Reactions that split larger molecules into smaller ones.
Label the diagram
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1Box 1
2Box 2
3Box 3
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