Enzyme Core Practical

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Affect of enzyme concentration to the rate of reaction

With the experiment of protein solution, in this case egg white added to different pepsin concentrations (0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%) shows, as the egg white is a protein and the pepsin works as an enzyme, how a higher pepsin concentration and therefore a larger amount of enzymes effect the rate of reaction.

An increased concentration of pepsin speeds up the time the mixture needs to come clear.

The egg white is our protein solution, because egg white is a typical protein with peptide bonds between its amino acids that can be broken by pepsin, a metabolism enzyme that works best under a pH between 1 and 5, and is destroyed at a pH of 6. Enzymes are proteins that work as biological catalysts to reduce the required activation energy to start a reaction. This allows reaction to happen even at lower temperatures than they actually need. Too high temperatures as well as the wrong pH can destroy the active side of an enzyme that is appropriate for the break down of substrates into products. That ability can make poisonous substrates and molecules harmless, because they are separated into two products, who then can be used for different things in the body. The active side on an enzyme has a specific shape which allows the joining with just one specific molecule. Therefore a lot of different enzymes with different fields of duties are in the body. First the key and lock theory explained the joining of the active side with a fitting substrate but after more study scientists agreed that this theory isn`t that likely because enzymes are even more specific and have to make sure that the molecule that connects with their active side is definitely the one that they are able to break down. A new theory, the induced fit model, assume that as soon as the substrate sticks to the active side of an enzyme and forms the enzyme/substrate complex, the active side changes slightly its shape and sticks even closer together with the substrate to insure that they fit together. As more enzymes are in a solution, the higher is the rate of reaction. This is because more active sides are available and ready to join together with the other molecules in the solution. Substrates can therefore faster find a fitting active side and be broken down. With keeping the amount of enzymes increasing, it will stop having any affect of the rate of reaction, as soon as all the limited molecules of the solution found their active side.

A pepsin moleculean egg white protein molecule

Induced fit model – substrate broken down

The constant factor was the amount of egg white solution (5cm3) in our six test tubes, the temperature and the pH of the enzyme solution. Therefore the six different concentrated pepsin solutions (0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%) are the independent factor with effects the dependent factor, the rate of reaction or the time till the mixture gets clean.

|Apparatus/ Equipment |Justification | |Egg white solution |Typical protein with peptide bonds | |Test tubes |-easy to separate the different mixtures | | |-good overview when a solution gets clear | |Labels |-to identify which concentration got clear when | |Test tube holder |-holds the test tubes | | |-makes it easy to compare the clearness of...
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