Lesson: Chapter - 5

Enzymes

Some chemical reactions simply happen when the two reactants come into contact. For example, you may be familiar with the bubbly “volcano” that forms when baking soda and vinegar are placed together in a glass. This reaction is spontaneous because it does not require outside energy to force it to occur.

Most reactions, however, require energy. For example, the chemical reactions that produce a cake do not take place when baking soda, flour, and the other ingredients of a cake are simply left in a pan on the kitchen counter. Heat is required to break the existing chemical bonds in the ingredients so that they can undergo chemical reactions and combine with each other in new ways.

In the laboratory, chemists use heat to create the activation energy needed to get nonspontaneous reactions started. Animals, however, can’t rely on internal Bunsen burners to get their chemical reactions cooking. In order to perform chemical reactions at low temperatures, the body uses special proteins called enzymes, which lower the activation energy necessary for chemical reactions to achievable levels. Enzymes lower the activation energy by interacting with the substrates, the primary molecules or compounds involved in the reaction. If you think of the activation energy needed for a chemical reaction as a mountain that the reactants have to climb, think of an enzyme as opening up a tunnel through the mountain. Less energy is required to go through the tunnel than to climb all the way up the mountain.

Video - Classification of Enzymes

Factors Affecting Enzymes

Like all proteins, enzymes have a unique three-dimensional structure that changes under unusual environmental conditions. Enzymes do not function well when their structure is altered.

Temperature and pH

Depending on where it is normally located in the body, an enzyme will have different temperature and pH values at which its structure is most stable. As conditions deviate from this point, the enzyme’s ability to help along reactions decreases.

Next to display next topic in the chapter.