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

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

5. 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

6. 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

7. 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

8. 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

9. Does this diagram show dehydration synthesis or hydrolysis?

10. 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?