Enzymes are arguably one of the most important catalysts in the human body. Without them we would be dead. Essentially they are proteins but their role is extremely important in catalysing reactions such as growth or digestion, we would sure miss them they were gone. Whilst we can agree that they are very important, the method as to how they work is debatable. For a reaction to start, the activation energy needs to be supplied, this is a certain amount that enzymes help the molecules achieve. However the method has been shortlisted to two hypotheses. The Lock and Key hypothesis and the Induced-fit hypothesis.
The lock and key hypothesis is the traditional and more accepted method. It works by reaching the active site. The active site is an area within the complex 3D tertiary structure of the enzyme, which has a shape that is complementary to the shape of the specific substrate molecule.
The way this woks is literally like a key entering a lock, likewise only a specific substrate will fit the active site of an enzyme. When the substrate is bound to the active site, an enzyme-substrate complex is formed. The substrate/substrates then react and the product/products are formed in an enzyme-product complex. The porduct/products are then released, leaving the enzyme unchanged and able to take part in subsequent reactions.
The substrate is held in such a way by the enzyme that the right atom-groups are close enough to react. The R groups within the active site of the enzyme will also interact with the substrate, forming temporary bonds. These put strain on the bonds within the substance which also helps the reaction along.
The other hypothesis is a more recent development from newer evidence from research. Evidence shows that the active site of the enzyme actually changes the shape slightly as the substrate enters. This is known as the induced-hypothesis and is a modified version of the lock and key hypothesis. The initial interaction between the enzyme and substrate is relatively weak, but these weak interactions rapidly induce changes in the tertiary structure of the enzyme. By putting strain on the substrate molecule. This allows bonds in the substrate to be weakened and effectively lower the activation energy for the reaction.
Research is very complex and time consuming, but it is very important. In this case it has allowed for a new model as to how enzymes lower activation energy to arise. Only further research will show a clear accepted model but for now there are two main hypotheses.