Enzymes Experiment

Enzymes Experiment

Introduction

Enzymes are biological catalysts that promote some of the thousands of

chemical reactions that occur in living cells. They are large

molecules that have a unique three-dimensional structure that allows

it to react with a specific substrate. It is hypothesized that pH

levels out of the normal range found in cells would denature the

enzyme, slowing the enzyme's reaction rates.

Hydrogen Peroxide (H2O2) is a poisonous chemical that is continually

being formed as a byproduct of reactions in peroxisomes of living

cells. Since it is poisonous, the cells must either rid themselves of

it or change it to something that is not harmful to the body, the

consequence of not doing so, ultimately being death. The enzyme

catalase is found in animal and plant tissues, and is especially

abundant in the liver. Catalase reacts with the H2O2 to form water and

oxygen:

2 H2O2 + Catalase à 2 H2O + O2 + Catalase

The amino acids forming the enzyme contain functional groups such as

carboxyl groups and amino groups. These functional groups are able to

react with excess H+ ions in solution, resulting in the disruption of

the enzymes' structure. Most enzymes, for example amylase, have an

optimum pH in the neutral pH range that resembles that of the cell

environment, usually being the neutral pH level of 7. However there

are exceptions depending on the environment that the enzyme must work

in. For example, pepsins, which are protein digesting enzymes found in

the stomach, have an unusually low optimal pH of 2.5.

In this experiment, catalase will be extracted from sheep liver. The

extracted enzyme will be mixed with a solution of known pH. The

reaction time of the enzyme will then be measured and graphed.

It is expected that the catalase would perform the most effectively,

with the quickest reaction time, in a pH range of 7, as that is the

physiological pH of most cells in the human body. It is also expected

that the reaction time will rise as the pH is raised or lowered away