The aim of this investigation is to find out the effect of pH on an enzyme activity (Catalase).

The effect of pH on the activity of catalase

This reaction is about enzyme catalase and how it is affected by pH. A catalase is an enzyme; an enzyme is a biological catalyst.

In this investigation catalyse will catalyse the Hydrogen Peroxide.

Hydrogen Peroxide Water + Oxygen

H2O2 H2O O2

In the human body a catalase is produced in the liver. It is needed in the liver because Hydrogen Peroxide is poisonous. Hydrogen Peroxide is thought to be made as a by-product of several reactions in cells. It must be decomposed instantly, before it can do any damage.

Enzymes break down the Hydrogen peroxide which relates to the kinetic theory. This is the change of state in terms of the movement and positioning of the particles. Therefore, the greater the amount of enzymes in contact with the Hydrogen Peroxide, the greater the amount of oxygen produced. This demonstrates the lock and key theory.

The three-dimensional structure of all enzymes can be affected by pH. Enzymes are made up of amino acids. Each amino acid has two groups (a -NH2 group and a -COOH group). pH is all about concentration of H+ ions. At low pH e.g. 3, the most common groups will be -COOH and –NH3+ . At neutral pH e.g. 7.5, the most common forms will be -COO and –NH3+ . At high pH e.g. 9 the most common forms will be -COO- and -NH2 .

Interactions between these positive and negative charges are very important. This is what holds the structure together in an enzyme. These links are known as salt links, salt bridges or electrostatic interactions, and involve a positive to negative attraction. If I was to change the pH it would alter the properties of these salt bridges. Even a slight alter away from the optimum pH might mean one of these salt bridges is affected and therefore the shape, activity and stability of the protein will also be affected.