Enzymes

Activity # 08

Enzymes

Objecctives

At the end of the experiment, the student should be able to:

1. carry out tests for enzyme activity and specificity.

2. learn the principles behind the color changes.

3. learn the principles behind the specificity of enzymes.

Introduction

Enzymes are biological molecules that serve as catalysts for many biological reactions that sustain life. They are special proteins that catalyze thermodynamically possible reactions so that the rate of reaction is compatible with the biochemical processes needed for the maintenance of the cell.

Enzymes are specific, unlike other inorganic catalysts, they only act on particular substances. Each enzyme has its own specific active site which binds to a specific substrate. The enzyme will not function if such binding will not occur. Some enzymes contain some metallic ions and still others are similar to conjugated proteins. The protein portion is called the ‘apoenzyme’ while the non-protein organic group is called ‘coenzyme’. The two together is called or forms the ‘holoenzyme’ – the active enzyme.

Results and Discussion

A. Preparation of Catalase

Buiret Test

Observation

Filtered potato extract Transparent, light violet liquid

While the majority of the extracted potato contains starch, a polysaccharide commonly found in plants, it also contains a very small amount of protein. For this reason, the extract has a positive result after the Biuret test is performed. Since the amount of protein is very minimal, addition of NaOH and CuSO3 only yielded a faint violet liquid.

Test for catalase activity

Observation

Filtered potato extract Evolved gas combusted; smoke observed inside the test tube. Clear liquid w/ light brown precipitate observed after adding benzidine

Most living things contain an enzyme called catalase. When peroxide is added to the starch solution, the catalase breaks down peroxide molecules into H2O and O2. The reaction is shown below.

The...