Page "Metabolism" Paragraph 7

Most of the structures that make up animals, plants and microbes are made from three basic classes of molecule: amino acids, carbohydrates and lipids ( often called fats ).

As these molecules are vital for life, metabolic reactions either focus on making these molecules during the construction of cells and tissues, or breaking them down and using them as a source of energy, in the digestion and use of food.

Many important biochemicals can be joined together to make polymers such as DNA and proteins.

These macromolecules are essential.