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Organisms are made of cells. Most organisms are multicellular and have cells that are specialised to do a particular job. Microscopes produce magnified images of cells so we can study them in detail.

The genetic code of all life on Earth is made from DNA. Enzymes are biological catalysts which speed up chemical reactions.

Respiration releases energy from glucose in the form of ATP. This occurs in all living cells. Aerobic respiration (with oxygen) releases more energy than anaerobic respiration (without oxygen).

Plants make food using photosynthesis. This food is important for the plants themselves and for organisms that feed on plants. Getting optimum rates of photosynthesis produces maximum plant yields.