1. AND CHEMICAL
REACTIONS

2. REACTIONS atoms must be balanced on both sides
of the equation in a chemical reaction
Balance the following equation:
Reactants Products
CO2 + H2O → C6H12O6 + O2
6CO2 + 6H20 → C6H O2

3. 2 TYPES OF CHEMICAL REACTIONS
1. Exothermic: Release Energy –
can occur spontaneously
give off energy

4. Example – digestive process releases energy from food
Energy-Releasing Reaction
Activation
energy
Reactants
Products

5. 2. Endothermic: Absorb Energy – need energy to occur store energy
Example – photosynthesis
Energy-Absorbing Reaction
Activation energy
Reactants
Products

6. Energy needed to start a reaction is called activation energy.

8. Provides a place for reactants (substrates) to react (active site)
HOW AN ENZYME WORKS
Provides a place for reactants (substrates)
to react (active site)
Active site
They fit together with the enzyme like a lock and key
forming an enzyme-substrate complex.

9. Enzymes are specific in their activity.
Enzymes lower
the activation
energy.
Enzymes speed up the rate of a reaction.

10. When the reaction is complete, the products are released and the
enzyme remains unchanged and
reusable.

12. ENZYME REGULATION
1. Change in temperature or pH can affect the enzyme.

14. Some enzymes (allosteric enzymes) can be
turned on or off by other proteins by
changing the enzyme’s shape.