Summary on Concept 5.5

Enzymes and Activation Energy

• To start a chemical reaction it is necessary to weaken chemical bonds in their reactant molecules. This activivation requires molecules to absorb energy.


• The energy that "starts up" the reaction is called activation energy.


• Heating up cells could cause a reaction that can destroy the cells delicate structures.


• Catalysts are compounds that speed up a reaction.


• The main catalysts of chemical reactions are specialized proteins called Enzymes.

How Enzymes work

• A specific reactant acted upon an enzyme is called an enzymes substrate.


• The Substrate fits in a particular region of the enzyme called the active site.


• A way inwhich a enzyme can lower activitation energy is by accepting two reactant molecules (substrates) The composition of these reactants allows them to react more easily.


• An enzymes structure and and shape are important to its functions.


• Like proteins, an enzyme's shape is sensitive to changes in its surrounding enviroment.

Concept Check

1.)Explain the role of activation energy in a reaction. How does an enzyme affect activation energy?

The activation energy plays a role in starting a reaction. Enzymes act as a catalyst of a chemical reaction, which means that enzymes speeds up the process of a chemical reaction.

2.)Describe how a substrate interacts with an enzyme.

As the substrate enter the active site, the shape of the active site changes so that the subtrate can fit tightly. When they fit together, it places certain functional groups that would catalyze the reaction.