Enzymes: Lab Report

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Introductory Biology 1

Biology 1003

Fall Term 2011

Lab Number: 3

Title: Cell Energetics: Enzyme Role in Biological Reactions

Name: Brandon Moore

Student Number: 100819124

Lab day and time: Wednesday pm

Date: Wednesday November 23, 2011


Enzymes are a key aspect in our everyday life and are a key to sustaining life. They are biological catalysts that help speed up the rate of reactions. They do this by lowering the activation energy of chemical reactions (Biology Department, 2011).

In chemical reactions bonds must be broken and new bonds must be formed. In order for this to occur the bonds must be made less stable. For bonds to become less stable a small input of energy is required and this is called the activation energy. In simpler terms, in order for a reaction to begin and proceed spontaneously a small input energy is required to give the reaction a push and get it started (Cooper, 2000).

As said before catalysts are chemical agents used to speed up the rates of reactions. The biological catalyst is a group of proteins called enzymes. Enzymes work by lowering the activation energy and making it easier for the reactants to obtain the necessary energy to break the kinetic barrier. Even though enzymes speed up the rate of reaction, they do not change the free energy of the reactants and the products (Russel et al., 2010).

Enzymes work by combining with reacting molecules at the active site. Each enzyme is specific to only one kind of molecule and can only bind to its specific molecule. The active site is a groove in the enzyme where the molecule will bind to; this is formed by the enzyme folding into a specific shape. When the enzyme is done and the molecules are then in the transitional state, which means the bonds are unstable and ready to be broken, the enzyme remains unchanged and can continue to bind to other molecules (Russel et al., 2010).

Enzymes induce the transition state by three major mechanisms. The first is by bringing the reacting molecules together. The reactants bind in the active site of the enzyme in the right orientation for catalysis to occur. The second mechanism works by the enzyme exposing the reactant molecule to altered charge environments. The third mechanism is by changing the shape of a substrate molecule (Russel et al., 2010).

The conditions being studied on how they affect enzyme activity are: concentration, ph, and temperature. As the concentration of enzymes increases the rate at which products are formed also increases. It is also true as the concentration of the substrate increases the rate of the reaction will also increase until the enzymes reach their maximum rate at which they can combine with the substrates. Each enzyme has a best possible pH where it works at its best. Anything that changes on either side of the optimum pH will decrease the rate of the reaction. Finally as temperature raises so does the rate of the reaction but only to a certain point. As the temperature raises the frequency and strength of collisions will increase, however if the temperature rises too high the hydrogen bonds of the enzyme break and it unfolds making it unable to accept any molecules due to its active site being destroyed.

To observe the effects of these three conditions on enzyme activity spectrophotometry is used. A spectrophotometer works by measuring the amount of light a compound in solution absorbs. As the concentration of the solution increases more light is absorbed (Biology Department, 2011).

The purpose of this experiment is to test and observe the effects of concentration, pH, and temperature on enzyme activity.


In part I of the lab obtain six small glass tubes in a test tube rack. After the six small tubes are obtained, add fifteen drops of distilled water to tube 1, ten drops to tube 2 and 3, five drops to tube 4, and no drops to tubes 5 and 6. Once distilled water is added five drops of the substrate solution...
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