AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Students should be able to explain the importance of sugars, amino acids,…
Full specification wording
Metabolism: Students should be able to explain the importance of sugars, amino acids, fatty acids and glycerol in the synthesis and breakdown of carbohydrates, proteins and lipids.
Metabolism includes both building up and breaking down substances.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 1 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Metabolism includes both building up and breaking down substances. Sugars, amino acids, fatty acids and glycerol are the small molecules used to synthesise larger storage and structural molecules, and they are also released when those larger molecules are broken down. Glucose molecules join by condensation reactions to form starch, glycogen or cellulose. Amino acids join in a specific sequence to form proteins. Fatty acids and glycerol combine to form lipids such as fats and oils. In breakdown, carbohydrates are hydrolysed to sugars, proteins to amino acids, and lipids to fatty acids and glycerol. These reactions are controlled by enzymes. Understanding this helps explain digestion, growth, repair, energy storage and the movement of substances in living organisms.
What earns the marks
- Sugars such as glucose are the building blocks for carbohydrates, including starch, glycogen and cellulose.
- Amino acids are the building blocks of proteins, joined in a sequence determined by genes.
- Fatty acids and glycerol combine to form lipids such as fats and oils.
- Breakdown reactions release these small molecules: carbohydrates to sugars, proteins to amino acids, and lipids to fatty acids and glycerol.
- The importance lies in growth, repair, energy storage and the release of usable molecules for respiration and other processes.
Common mistakes and how to put them right
Saying proteins are made from sugars.
Put it right by stating that proteins are synthesised from amino acids.
Confusing the breakdown products of lipids with those of carbohydrates.
Put it right by stating that lipids break down to fatty acids and glycerol, while carbohydrates break down to sugars.
Describing synthesis as digestion.
Put it right by explaining that synthesis builds larger molecules from smaller ones, whereas digestion is a breakdown process that releases smaller molecules.
Exam tips
- Use a two-column table for synthesis and breakdown, listing the small molecules and the large molecules for each row.
- When explaining importance, link each molecule to a named process such as growth, repair, storage or respiration.
- Use the terms monomer and polymer only if you can also name the specific examples, such as glucose and starch.
Try the lesson
The start of the Metabolism: Students should be able to explain the importance of sugars, amino acids, fatty acids and glycerol in the synthesis and breakdown of carbohydrates, proteins and lipids. lesson, made from checked teaching notes for this specification point.
Have a go first
Which small molecule is joined together many times to synthesise a carbohydrate such as starch?
Listen
Metabolism includes both building up and breaking down substances. Sugars, amino acids, fatty acids and glycerol are the small molecules used to synthesise larger storage and structural molecules, and they are also released when those larger molecules are broken down. Glucose molecules join by condensation reactions to form starch, glycogen or cellulose. Amino acids join in a specific sequence to form proteins. Fatty acids and glycerol combine to form lipids such as fats and oils. In breakdown, carbohydrates are hydrolysed to sugars, proteins to amino acids, and lipids to fatty acids and glycerol. These reactions are controlled by enzymes. Understanding this helps explain digestion, growth, repair, energy storage and the movement of substances in living organisms. A strong answer earns marks for these points. Sugars such as glucose are the building blocks for carbohydrates, including starch, glycogen and cellulose. Amino acids are the building blocks of proteins, joined in a sequence determined by genes. Fatty acids and glycerol combine to form lipids such as fats and oils. Breakdown reactions release these small molecules: carbohydrates to sugars, proteins to amino acids, and lipids to fatty acids and glycerol. A common slip: Saying proteins are made from sugars. Instead, stating that proteins are synthesised from amino acids. Exam tip: Use a two-column table for synthesis and breakdown, listing the small molecules and the large molecules for each row.
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Key words
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Metabolism
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Building blocks of carbohydrates, proteins and lipids
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Enzyme-controlled reactions
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Growth, repair and energy storage
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See every definition
- Metabolism
- Includes both building up and breaking down substances, with synthesis and breakdown controlled by enzymes.
- Building blocks of carbohydrates, proteins and lipids
- Sugars, amino acids, fatty acids and glycerol are the small molecules used to synthesise larger storage and structural molecules.
- Enzyme-controlled reactions
- Both synthesis and breakdown are metabolic reactions controlled by enzymes.
- Growth, repair and energy storage
- Understanding synthesis and breakdown helps explain digestion, growth, repair, energy storage and the movement of substances in living organisms.
Label the diagram
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