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Unit 3

3.2 Enzyme Catalysis

2 min readmay 30, 2020


Caroline Koffke

AP Biology 🧬

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A catalyst is a substance that increases the rate of a reaction. An enzyme is a biological catalyst, a specific subcategory. Enzymes function by decreasing the activation energy necessary for a reaction to occur. This can be shown in the graph below. As portrayed, the energy associated with reactants and products of the reaction does not change due to the presence of the enzyme.

Image courtesy of WikiMedia Commons.

Enzyme Reactions

An enzyme simply lowers the amount of energy that needs to be input in order to start the reaction. This often but does not always make the reaction occur more quickly. The most important thing to remember is that the reaction occurs with less energy than it would without an enzyme. The reaction that is catalyzed by an enzyme would occur without the presence of the enzyme as well, the reaction would just be more energy costly.
It is also important to remember that enzymes are recycled and may be reused over and over again until they denature. Because they are not a product or reactant, they are not altered during the course of the reaction. They also do not show up in the equation of a reaction because they are present at the beginning and end and, therefore, cancel each other out.

Competitive and Noncompetitive Inhibitors

A few substances act to inhibit or activate the processes of enzymes. While there are many environmental factors that can alter an enzyme’s ability to function, explained next, there are also certain molecules that can act to change the process as well. A chart of these molecules is shown below.

Image courtesy of WikiMedia Commons.

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