(3) Enzyme-substrate specificity and activity

Explain Enzyme-Substrate specificity 

Enzymes make it easier for a reaction to take place. 

A substrate is a molecule upon which an enzyme acts. It binds to a specific area of an enzyme called the active site. 

The substrate fits into the active site of the enzyme as a key fits into a lock. This is called the lock and key model of enzyme action. Shown below. 

The 3 dimensional structure of a protein (ENZYME IS A PROTEIN) determines the shape of the active site. The substrate fits into the active site and reaction proceeds. 

If a molecule has the "wrong" shape it cannot fit into the active site and will not react. 

Therefore an enzyme only works with a specific substrate and only catalyzes a specific reaction. 

Enzyme specificity is due to the complementary shape of the active site and


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