1. ENERGY & CHEMICAL REACTIONS
I. Energy
– is the ability to move or change
matter
- it is stored or released by chemical
reactions
- it exists in many forms; ex: light,
heat, chemical energy,
mechanical energy, and
electrical energy

2. - energy powers the chemical reactions that occur in cells
Chemical reactions are summarized by
chemical equations, which are written in
the following form:
Reactants Products
(starting material) (newly formed substances)
ex: NaCl Na Cl-
H2O

3. II. Energy in Chemical Reactions
In chemical reactions, energy is either absorbed or released as chemical bonds are broken or new ones are formed.
Energy Releasing vs. Energy Absorbing
Exergonic
Endergonic

4. Activation Energy
Energy is needed to start a chemical reaction. The energy needed to start a chemical reaction is called the activation energy. It is simply a chemical “push” that starts a chemical reaction.

5. Biochemical reactions
– chemical reaction that occur in cells
- they occur quickly and at relatively
low temperatures because of the
action of many enzymes
enzymes – are substances that increase
the speed of chemical reactions
- most enzymes are proteins
- they are catalysts, substances that
reduce the activation energy of a
chemical reaction

6. Enzymes Lower Activation Energy

7. III. Enzyme Specificity
substrate – a substance on which an enzyme acts during a chemical reaction
ex: 2H2O H2O + O2
substrate
starch glucose
active site – a site on the enzyme
that is specific for a certain
catalase
amylase

8. ENZYME Breaks Down Lipase Fats & oils Amylase Starch Maltase Maltose
Protease
Protein
Catalase
Hydrogen peroxide
Carbohydrase
Carbohydrates
Lactase
Lactose

9. Factors that affect enzyme activity:
1. temperature
2. pH level
3. enzyme & substrate concentration
Enzyme-Substrate Complex