How do enzyme controlled reactions work?

Firstly, an enzyme is a specific protein with a unique shape. The main aim of an enzyme is to CATALYSE a reaction. This means, the reaction is sped up, but the concentrations of reactants or products are unchanged. One enzyme will only react with one substrate therefore these reactions are very specific. There are two main ways in which the enzyme and substrate interact 1) Lock and key hypothesis 2) Induced fit hypothesis

The first is when the shape of the substrate precisely fits into the ACTIVATION SITE of the enzyme. As competitors have been found to also initiate enzymatic reactions, the substrate and enzyme may be a little flexible meaning an induced fit model.

So: E+ S -> ES.

This however is a very high energy reaction and therefore needs a huge input of energy. This is called the activation energy. The transition state formed is in higher in energy than the substrates or the products.