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Paul Haycock Biology Coursework ????????????????????????????????? ??????? ?????????????????????????????? ???????????????????? An enzyme is a biological catalyst. This means that they speed up chemical reactions in the body without changing themselves. Enzymes are protein molecules which are usually denatured (damaged) by temeratures above about 45C. Enzymes work, like all catalysts, by providing a different pathway for the reaction to follow. The new reaction path has a lower activation energy and so the rate of the reaction is much faster than if no enzyme is present. Enzymes catalyse reactions using a lock and key mechanism. The reactants fit exactly into the enzymes active site and when the reaction has taken place the products are relesed from the enzyme, allowing it to catalyse another reaction. In humans enzymes are made in the pancreas, passed into the digestive system and secreted onto food in the stomach. This helps braek down the larger food molecules into smaller ones so that they cross...

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