Metabolism

Metabolism is the term used for all the chemical reactions that happen inside an organism's body.

These reactions build up molecules, and break them down. Polymers are the large, complex molecules built from smaller, less complex monomer molecules. They are controlled by enzymes.

  • Starch and cellulose are polymers made from the glucose monomer.
  • Proteins are polymers of the amino acids monomers.
  • Lipids are made from two different molecules called fatty acids and glycerol. Because of this lipids are not polymers.

We can show the possible reactions of any substance in a cell in a diagram. These are useful because they are a visual reminder of all the metabolic processes that occur.

Metabolism in plants

Build up of molecules in plants

Glucose is made by plants during photosynthesis. Plants are then able to make larger, more complex molecules with glucose.

This diagram shows the metabolism of glucose in plants after it has been produced during photosynthesis.

It shows that glucose is used:

  • to make starch and cellulose
  • in the process of respiration
  • to make amino acids and therefore then proteins
  • to make lipids (fats and oils)
A spider diagram showing the different cycles of Gluecose.

Breakdown of molecules in plants

Plants are also able to breakdown the larger, more complex molecules they have made to make glucose. This diagram shows the metabolism of glucose in plants - how glucose can be made from starch, lipids and amino acids, and is used in the process of respiration.

A flow chart showing the different cycles of Gluecose.

Metabolism in animals

Build up of molecules in animals

Animals obtain glucose in their diet. During metabolic reactions, animal cells use glucose:

  • in the process of respiration
  • to make glycogen which is stored in the liver and muscle cells
  • to make lipids from fatty acids and glycerol
  • to make proteins from amino acids
A flow chart showing the different cycles of Glucose.

Break down reactions in animals

All cells require glucose for respiration. Animals can convert glycogen into glucose when they need a short term supply of energy and they have run out of glucose. After animals have broken down all its glycogen, they will breakdown lipids and then proteins to supply the glucose needed for respiration.

A flow chart showing the different cycles of Glucose.
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