Enzymes, a kneed to know.

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Enzymes, what you kneed to know...

What is an enzyme?

     Just in case you were asleep for the whole of GCSE Biology... An enzyme is a protein that speeds up the rate of  a reaction. Enzymes are either classed as being intracellular, an enzyme that is produced and then function within the cell, or extracellular which are produced and then re-located and function outside of the cell. It is also important to note that an enzyme is not used up by any of the reactions that is catalyses. 

A couple of useful terms... 

     Here are a few words that are likely to crop up now and again, so its worth making a note of them. 

Metabolism- This describes all the chemical reactions within a cell. 

Catabolic- A reaction where substances are broken down to create energy.

Anabolic- A reaction where substances are joined together to create energy. 

Exergonic- A reaction that releases energy.

Endergonic- A reaction that takes in energy. 

Substrate- A molecule that an enzyme catalyses. 

Product- (sucking eggs much...) A substance that is produced by the reaction. 

So what does an Enzyme do?

     An enzyme speeds up a chemical reaction, as well you know... But how? Well the enzyme is a protein, which is a 3D molecule and as such, has a section that binds with the substrate in order to catalyse the reaction. This area is known as an 'Active Site' and is specific to the substrate which the enzyme reacts with. The reason the substrate joins with the active site is that the active site has a complimentary shape to the substrate- same as. They also have the opposite ionic charge, attracting the substrate molecule to them. 

So, I feel an analogy is called for in order to better understand this challenging concept... 

Well Scientists have done it for me. There are two different theories that you kneed to know about and both have a handy analogy, thought up by Biology teachers with no life, no doubt...  

The 'Lock and Key' Theory: 

     This is the idea that the reaction between the enzyme and its substrate is like that of a lock and a key. The lock has a series of pins that are specific to a  particular key. The theory goes that the enzyme is like a lock (having a specific shape) which is specific to one substrate only- the key. The tumblers of the lock represents the active site and only the right substrate will have a complimentary shape and unlock the lock. 

The 'Induced Fit' Theory:

     A similar theory but the idea this time is that the enzyme is roughly the right shape but changes slightly when it meets the substrate in order to create a perfect fit. If you think about a woolly glove. It has 5 fingers and is roughly the right shape to fit your hand, however when you put your hand into it, it changes (stretches slightly) so that your hands…


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