Chemical reactions involve the rearrangement of atoms in substances to form different products. Chemical equations show the reactants and products, with the same number and type of atoms on both sides. Chemical reactions require activation energy to occur, and can release or absorb energy. Enzymes are biological catalysts that lower the activation energy needed for reactions in living things by binding to reactants at an active site and facilitating the formation of products.

1. 6.2 Chemical Reactions

2. Chemical Reaction;
• Process by which atoms or groups of
atoms in substances are reorganized
into different substances

3. Chemical Equations;
Reactants --> Products
Example: The reaction that forms water
2H2 + O2 --> 2H2O
How many of each atom is on the reactant
and the product side of this equation?

4. 2H2 + O2 --> 2H2O
REACTANT: PRODUCT
4 Hydrogen 4 Hydrogen
2 Oxygen 2 Oxygen
• Matter cannot be created or destroyed
in chemical reactions. Therefore, the
reactant side will always equal the
product side.

5. Energy of Reactions
• The minimum amount of energy needed for
reactants to form products in a chemical
reaction is called the activation energy.
• For example, a candle will not burn until you light its
wick. The flame provides the activation energy for
the reaction of the substances in the candle wick with
oxygen.

6. Energy in Reactions
• Chemical reactions can be;
Exothermic; releasing energy
Endothermic; absorbing energy

7. Enzymes
• To speed up a chemical reaction,
scientists use catalysts
• A catalyst lowers the amount of energy
needed to start a chemical reaction.
• In living things, these catalysts are
called ENZYMES.

8. How Enzymes Work
1.The enzyme will
bind to a substrate
(reactant) like a lock
and key

9. • The location of where an enzyme binds
to a substrate is called the active site.

10. How Enzymes Work
2. Once the enzyme and substrate
combine, the enzyme-substrate
complex is created.
3. This complex helps to break bonds in
the reactants and form new bonds,
changing the substrates into products
4. The enzyme then releases the product

11. Draw this on your paper
Enzyme + Substrate Enzyme Substrate enzyme + product
Complex