Chapter 5.5 Summary

• to start a chemical reaction, it is first necessary to weaken chemical bonds in the reactant molecules
• activation energy is "start-up" energy
• one way to provide activation energy is to heat up the mixture of molecules
• heating up a cell would cause many unnecessary reactions
• the main catalysts of chemical reactions in organisms are specialized proteins
• catalyst is a compunds that speed up chemical reaction
• enzyme doesn't supply activation enrgy
• each enzyme catalyzes a specific kind of chemical reaction

• the shape of each enzyme fits the shape of only particular reaction molecule
• specific reactant acted upon by an enzyme is substrate
• the substrate fits into a particular region of the enzyme is active site
• as substrate enters, the shape change slightly
• tighter grip weakens the bonds
• another way that an enzyme can lower activation energy is by accepting two reactant molecules into adjacent sites
• enzymes structure and shape are essential to its function
• enzyme changes shape depending on the enviornment

Concept Check 5.5



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

Activation energy's role is to activate the reactants and triggers a chemical reaction. Enzymes does effect activation energy by lowering the energy requirement of the barrier so reactons can react at a normal temperature.



2. Describe how a substrate interacts with an enzyme.

A substrate interacts with an enzyme by entering the enzyme's active site, and active site changes shape. This help the subtrate to fit better to enzyme's active site. Then it places certain functional groups of the active site in position to catalyze the reaction.