2. Chemical Reactions
Chemical reactions = the breaking and creating of bonds between different substances (this requires energy)
Activation energy = The amount of energy needed to make a chemical reaction start

3. Chemical Reactions
Reactants (substrate): substances that are changed during a reaction
Products: substances that are made by a chemical reaction
reactants
products

4. Types of Reactions Overall, reactions absorb or release energy.
Endothermic: absorbs energy
Ex. Photosynthesis
Exothermic: releases energy
Ex. Cellular Respiration
EXOTHERMIC
ENDOTHERMIC
Less energy in products than reactants
More energy in products than reactants

5. Key Biochemical Reactions
6CO2 + 6H2O  C6H12O6 + 6O2 Photosynthesis Energy is stored as sugar, therefore it is an ENDOTHERMIC reaction C6H12O6 + 6O2  6CO2 + 6H2O Cellular Respiration Energy is released as ATP when sugar is broken down, therefore it is an EXOTHERMIC reaction

6. Enzymes
Enzymes are a type of PROTEIN that speed up biochemical reactions by lowering the activation energy.
Because they speed up reactions, they are called catalysts.
Enzymes are specialized molecules that bind to reactants (aka, substrate) and help to break or form bonds. Then they release a newly created product.
Enzymes are not changed in a reaction and can be used over and over again!

7. Enzymes Enzymes are very specific
They have an active site that fits only one substrate (reactant)
This is known as the lock and key model
substrate
(reactant)
active site
enzyme

8. Enzymes Enzymes can break bonds in a substrate to form two products
(Bonds breaking)
enzyme

9. Enzymes Enzymes can make bonds between substrates to form one product
(Bonds forming)
enzyme

10. Denaturation
Enzyme’s active site gets deformed and loses its specific shape  causes a loss of biological activity
Caused by: extreme changes in pH, temperature, ion strength, and solubility
Enzymes can be “renatured” to their original shape but not always
Normal enzyme
Denatured enzyme

11. Ways to change the rate of a chemical reaction
Temperature = increasing temperature increases the rate of the reaction
Molecules are moving FASTER and colliding more with each other
2. pH = how acidic a solution is
Most enzymes only work at very specific pH so if the pH changes it can affect speed of reaction

12. Ways to change the rate of a chemical reaction
3. Substrate Concentration = the higher the amount of substrate, the faster the reaction
Due to more particle collisions
4. Catalysts = (like enzymes) speed up reactions
Lower activation energy needed for the reaction to start
5. Competitive Inhibitor = slows down reaction
Competes with substrate for the active site on the enzyme