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Some proteins are made first as an inactive form, and later trimmed into a smaller active form. For example insulin, the hormone that regulates your blood sugar levels, is produced from a larger inactive molecule. Other proteins, for example the enzymes that control the rate of chemical reactions in your body, are also first made in an inactive form. Your cells can activate these enzymes as and when they are needed.

Computer graphic showing a part of the molecule of human insulin.
Computer graphic showing a part of the molecule of human insulin.
Alfred Pasieka/Science Photo Library

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