Hillsborough Community College - Ybor City Campus
1025C Laboratory Exercise 3: Characteristics of Enzymes
Introduction
What are Enzymes?
Enzymes are very large and complex proteins that that function as catalysts. They are synthesized by the cell to perform very specific functions. Each type of enzyme has a very specific shape (conformation) which provides its specific function. The shape of an enzyme molecule is determined and maintained by many weak intermolecular interactions between many different parts of the molecule.
A catalyst is a material that donates energy to reactants in order to reduce their activation energy. In other words, they allow reactions to occur with less energy input (i.e. more quickly or at lower temperatures). The very specific shape of enzymes allows them to “fit” into a reaction and reduce the energy necessary for the reaction to occur. If their shape is changed, their ability to function as a catalyst is reduced or eliminated. As biological catalysts, enzymes are important because they speed up the rate of the reaction they catalyze that would otherwise be too slow to support life.
Factors Affecting Enzyme Activity
The rate at which an enzyme works is influenced by several factors including temperature and pH.
Enzymes are most effective as catalysts under optimum physical and chemical conditions; as conditions change away from optimum, enzyme activity decreases (Figure 1.). Changes in various environmental factors, such as temperature or pH, may affect proteins by altering their shape; with loss of shape comes loss of function causing the protein to become denatured. Denaturation is often a reversible process.

Figure 1. Effects of Variable Temperature and pH on Enzyme Activity

The Effects of Temperature on Enzyme Activity
Under ordinary conditions, at any given temperature, molecules possess a range of kinetic energy
(Ek). A portion of