1. Enzymes

2. Chemical Reactions Energy stored in chemical bonds
When bonds broken = Energy released (heat & light)
Activation Energy: amount of energy needed to start a reaction

3. Exothermic Reactions Exo = exit; thermic = heat
Defined: Release more energy than it absorbs
Light & heat
Ex: Cellular Respiration
Process that creates energy for cells
Chemical energy released for cells…
Heat energy released for warmth

4. Endothermic Reactions
Endo = within; thermic heat
Defined: Absorb more energy than it releases
Ex: Photosynthesis
Sunlight is absorbed by plants…to create energy as glucose

5. Enzymes Activation energy usually comes from an increase in temp
Slow process
Catalyst: substance that decreases the activation energy needed to start a chemical reaction
Speeds up reaction
Enzymes reduce energy needed (activation energy) to start a chemical reaction

6. Controlled Settings Human body ~98.6°F
Can’t raise body temp to start reactions.
Internal reactions would be too slow to sustain life without a catalyst
Ex: Saliva
Breaks down starch 1,000,000x faster with amylase

7. Enzyme Structure
Enzyme shape allows specific reactants to bind together
Reactants = substrate
Ex: Amylase & starch: Starch is the substrate because it binds to amylase
Substrates binds to activation sites on the enzyme (key fitting into a lock)
Once binded to enzyme, substrates bonds weakened
Substrates bonds break
Substrates re-bond to each other

8. Does this diagram show dehydration synthesis or hydrolysis?

9. Kobe Kuiz 1) How do enzymes speed up chemical reactions?
2) What is released when chemical bonds are broken?
3) Why is photosynthesis an example of an endothermic reaction?
4) Why is cellular respiration an example of an exothermic reaction?
5) Besides enzymes, what else is often a catalyst that speeds up reactions?
6) What are the molecules called that react with enzymes?
7) What do enzymes weaken between molecules?