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Biological definition help

what are enzyme-controlled reaction, enzyme activity, and enzyme action?
Here are some notes I made today on enzymes following the AQA A-level biology specification. I hope they can be of some help:

- Many proteins are enzymes
Enzymes are globular proteins that act as catalysers. Enzymes work by lowering the activation energy needed for the reaction to take place. With out enzymes reactions would happen to slowly to sustain life.
A specific region of the enzyme is functional, this is known as the active site. The active site consists of depressions that are complimentary to the substrate (the molecule on which the enzyme acts on). When the substrate fits into the enzyme’s active site this forms an enzyme-substrate complex.
The induced fit model of enzyme action:
-This is a scientific model. It suggests that the proximity of the substrate leads to a change in the enzymes active site.
-The enzyme is flexible and can mould itself around the substrate. The enzyme has a certain general shape and this alters in the presence of the substrate. As it changes shape the enzyme putts strain on the substrate molecules which distorts its bonds. This consequently lowers the activation energy.
-Any change in the enzymes environment (pH or temp) can result in a change of the enzymes active site- making the enzyme unable to form an enzyme-substrate complex. The induced fit is changed.

I also have notes on factors affecting the rate of activity if you need it. Hope it helps at all!

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