1. Energy & Enzymes

2. Recall… All living things need a source of, and use, energy
Energy is used in series of reactions called metabolism

3. Law of Conservation of Energy
Energy CANNOT be created or destroyed…
…it can only CHANGE form.
The amount of energy in the universe remains the same over time.

4. Chemical Reactions
A process that changes one set of chemicals into another set of chemicals.
Can be
Slow: ex: iron + oxygen  rust
Fast: ex: Hydrogen + Oxygen  explosion

5. Chemical Reactions CO2 + H2O H2CO3 Reactants on the left
Products on the right
CO2 + H2O H2CO3

6. Chemical Reactions + Energy
Every chemical reaction involves a transfer of energy
Can be:
Endergonic: absorption of energy
Exergonic: release of energy

7. Endergonic Reaction Products have more energy than the reactants
Energy is absorbed!
Example: photosynthesis

8. Exergonic Reaction Products have less energy than the reactants
Released as heat, light, or electricity
Examples: Glow sticks, Hot hands (Exothermic)

9. Vocabulary
Activation Energy: Amount of energy needed to start a reaction
Catalyst: anything that lowers the amount of activation energy needed
Unchanged or consumed during a reaction

10. Enzymes PROTEIN catalyst found in living things (biological catalysts)
HINT: Enzymes generally end in -ase (Ligase, primase, lactase)
Enzymes work as lock
and key
Image from:

11. Enzyme Specificity
Lock and key: each enzyme is specific lock that only fits 1 key (substrate)
Substrate= reactant on which enzyme acts
Area on the enzyme to which substrate “fits” is the active site

12. How enzymes work

13. Protein Denaturation Denature: To change a protein’s shape
Example: scrambled eggs
Recall that enzyme activity depends on shape…
Shape changes, enzyme can no longer function

14. What can denature a protein?
Change in temperature (too hot, too cold)
Change in pH

16. Enzyme inhibition
Inhibitors: substance that prevents enzymes from working
Competitive inhibition: Competes with substrate
Noncompetitive inhibitors: Binding changes active site