Enzymes are important to cells because they allow both the making and the breaking up of bonds. This would happen naturally and over time, but cells do not have the time to wait years, sometimes hundreds, for that to happen. With the use of enzymes, such tasks can take less than a second. This happens because enzymes are catalysts, and are able to speed up reactions. Enzymes, remaining unaffected by the process of catalysis, can continue to perform their function multiple times.
However, like most things, breaking and making bonds require energy. This energy causes substrates to change. The transition state is when substrate bonds are able to break up by themselves. Enzymes help bringing substrates to the transition stage by slowing down their activation energy. There are four ways by which the enzymes can do this, and they do not necessarily do only one at once.
The first way is by helping the substrates to bind together. It is easier for substrates to react if they are closer together, thus bringing on the transition state. The second way is by repositioning them. Substrates do not travel in a particular direction and so if they are repositioned so that they collide, they will react. Another way to cause reactions is using an induced-fit model. This means that the enzyme changes its shape to better fit the substrate and make for a stronger bond. Finally stopping water molecules from getting through and disrupting the reactions will help binding occur.
There are multiple things that can affect the way that enzymes function, namely temperature, pH, and salinity. When heat is added to enzymes it increases the rate of enzyme activity because more energy is being added to them and therefore the enzymes are able to better help substrates to come together. However, too much heat can cause enzymes to denature and stop functioning.
The tolerance of different pH levels for enzymes varies. The majority of enzymes function best at a neutral pH between 6 and...