What is metabolism?
Metabolism is the term for all of the chemical activity that takes place inside the cells. Metabolism breaks down more complicated substances obtained from food. This allows these substances to be changed into other materials that the body needs.
What are the essential substances the body needs for life?
Apart from oxygen, the human body needs food. Your food contains fats, proteins, carbohydrates and fibre, as well as vitamins and minerals. You need all these substances to stay healthy. They are first broken down in the process of digestion. They are then built up again inside the cells to make useful substances.
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