B4 - Ocr 21st century science

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  • Created by: Manisha
  • Created on: 06-05-14 17:47



What they do

·         biological catalysts thats speed up chemical reactions

·         they are proteins- large molecules made up of long chains of amino acids

·         they can break up molecules or build them up to create a larger one


How they work

·         lock and key theory

1.       each enzyme has an active site with a specific shape- the reaction takes place within the active site

2.       a substrate which has the same shape as the active site will fit into that specific enzyme

3.       this means that each enzyme has a specific substrate which will fit into it

4.       after the substrate fits in the enzyme breaks the molecule and the product leaves the active site

·         the active site can be used again after the reaction has taken place


Factors affecting enzyme activity

·         Temperature- each enzyme has an optimum temperature

1.       if the temeprature is below this amount then enzyme activity will be less energy to fuel the reaction therefore there will be less collisions.

2.       is the temperature reaches above the optimum temperature then the active sites of the enzymes will denature this means that the bonds holding the active site will break teherfroe it will change shape. this means that the substsrate will not fit into the active site therefore tehre will be no enzyme activity

·         PH also affects enzyme activity in a similar way      


In our body

·         optimum tempertaure is 37 degrees in human body- enzymes work well and speeds up chemical reactions

·         is


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