1. Chemical Reactions

2. Chemical Reactions
Chemical Reaction: process that changes one set of chemicals into another set of chemicals
Reactants - elements or compounds entering the reaction
Products - elements or compound formed by the reaction
Break bonds in reactions and form new bonds in products
CO2 + H2O  H2CO3
H2CO3  CO2 + H2O

3. Energy in Reactions
Chemical reactions can release energy or absorb energy when chemical bonds are formed or broken.
Reactions that release energy occur spontaneously.
Heat, light, or sound
Reactions that absorb
energy need a source
of energy to begin.
2H2 + O2 –> 2H2O

4. Activation Energy Activation Energy: energy need to start a reaction
Cellulose, in paper, burns in the presence of oxygen and release heat and light, but requires the energy of match to start the reaction.
 Catalysts: a substance that speed up the rate of chemical reactions;
Lowers activation energy
Use catalysts when activation energy is too great or reaction is too slow

5. Ea

6. Enzymes Enzymes: protein catalyst that speed up reaction inside cells
Specific: each enzyme only catalyzes only one reaction
Each enzyme has a specific, complex shape
names end in -ase

8. Enzyme Action
Enzymes provide a site where reactant can come together to react  reduces energy need
substrates: reactants of enzyme-catalyzed reaction
substrate binds to the active site

10. Enzyme Action Regulation of Enzyme Activity
lock & key: which have complementary shapes
once the substrate binds to the enzyme, it becomes Enzyme-Substrate Complex
they remain bound until the reaction occurs
after which, the products are released
the enzyme can start anew
Regulation of Enzyme Activity
affected by temperature & pH

12. Enzyme Animation