ENZYME REACTION

Enzymes are LARGE protein molecules folded up into tertiary structures with active sites that have unique shapes. Substrates are reactants in the reaction catalyzed by the enzyme. These substrates fit into the active site of the enzyme like a KEY fits into a LOCK. Only one specific substrate is acted upon by any single enzyme. Enzymes have specific jobs they do within a cell. Examples you have seen earlier in the course include RNA and DNA polymerase. Each polymerase builds one particular polymer. In the next unit on digestion, you will learn the function of many digestive enzymes and their specific substrates. Amylase for starch, Peptidase for peptides, Lipase for fats, Nucleases for DNA and RNA, and so on.

When an enzyme collides with a substrate molecule an enzyme-substrate complex forms. The active site on the protein enzyme interacts with the substrate and catalyzes the reaction (helps it along) by creating a lower activation energy for the reaction. This lower activation energy is often a result of the favourable geometry that results between substrate molecules allowing them to react more easily. Sometimes this involves a change in shape within the active site. Following the reaction, new products leave the enzyme and the process starts again with a new substrate molecule.