As the Enzyme-Substrate Complex forms, interaction between the R groups of the enzyme and the atoms of the substrate can break, or encourage the formation of bonds in the substrate molecule, forming one or multiple products.
Enzymes operate by reducing activation energy. In terms of the Enzyme-Substrate Complex, this is done through lacing strain upon the original bonds, through the enzyme and substrate molecules binding together, and the way in which the substrate is held allows the molecules to react more easily. In turn, this is lowering the activation energy, allowing the reaction to proceed faster.
The course of an enzymic controlled reaction is quite simplistic in theory. The rate of such a reaction is always fastest at the beginning. This short period is called the initial rate of reaction, and lasts for approximately 30 seconds.
When investigating the effect of enzyme concentration it is fairest to look at initial rate of reaction, as once the reaction is underway, the amount of substrate available in the reaction begins to vary, as substrate is converted to products at different rates, all depending upon concentration.
When the Enzyme-Substrate Complex is initially formed, there are a large number of substrate molecules available, meaning every enzyme molecule has a substrate molecule in its active site. This allows for the V Max rate of reaction, V Max being where the enzyme is working at its maximum possible rate. Rate of reaction depends upon the number of enzyme molecules available, and the speed at which the enzyme molecules convert substrate molecules into products. As the reaction continues, there are gradually fewer substrate molecules, meaning the speed of the reaction will decrease until the reaction eventually ceases.
Reaction rate is directly proportional to enzyme concentration. The more enzyme molecules available, the more active sites available for the substrate molecules to bind with. This means there is a quicker rate of reaction. The reverse is also true: the fewer enzyme molecules available, means that there are fewer active sites available for the substrate molecules to bind with. This causes a reduced/slower rate of reaction.
Therefore, in relation to this investigation, the higher the concentration of the enzyme means that there will be more active sites and enzyme molecules available. This results in a quicker rate of reaction. . Once again, the reverse is also true: the lower the concentration of the enzyme means that there will be fewer active sites and enzyme molecules available. This will result in a slower rate of reaction.
Using the theoretical background to this investigation, I predict that enzyme concentration will have the following effects on an enzymic controlled reaction:
- The higher the enzyme concentration, the quicker the rate of the reaction.
- The lower the enzyme concentration, the slower the rate of the reaction.
During this investigation, I will be controlling the following variables:
- Temperature (consistent at 40 C).
- Time of recording results (every 30 seconds for 5 minutes, including a reading at 0).
Prior to this investigation, I carried out the experiment that I will be using for my practical assessment to familiarise myself with the method. However, in my preliminary experiment, I focussed upon identifying the course of an enzyme-controlled reaction. For this investigation, I will be altering the concentrations of enzyme, temperatures, and times of recording results, from those used in my preliminary experiment. I will be using 5 different enzyme concentrations, opposed to the single concentration included in the preliminary experiment, and I will be concentrating upon one particular temperature, being 40 C. In order ensure the validity of my experiment; I will take three recording of each enzyme concentration at 40 C, instead of one, as in my preliminary experiment.
