Enzymes are biological catalysts for chemical reactions, produced by living things
Catalysts are substances which speed up reactions but are not changed or used up in the reaction
They are made from proteins which are made from chains of amino acids, folded into different shapes for different jobs
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Lock and Key Model
A substrate is a molecule that is changed in a reaction
Every enzyme molecule has an active site: where the substrate joins to the enzyme
Enzymes normally only speed up one type of reaction because the substrate has to be the correct shape to fit the active site
This is called the "lock and key" model because the substrate has to fit the active site like a key in a lock
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Temperature and Enzyme Activity
Temperature affects enzyme activity: at first a higher temp increases the rate, because the enzymes/substrates have more energy and are more likely to collide into enzyme-substrate complexes
If it gets too hot, bonds holding the enzyme together start to break which changes the shape of the enzyme so the substrate won't fit properly and the enzyme becomes denatured
Every enzyme has an optimum temperature at which they work best, usually around 45°
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pH and Enzyme Activity
If the pH level of the environment is too high or too low, it interferes with the bonds holding he enzyme together
This changes the shape of the active site and again denatures the enzyme
All enzymes have an optimum pH that they work best in, usually about pH 7 (neutral) but not always
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