1. Chemical Reactions and Enzymes

2. Chemical Reactions
A process that changes or transforms one set of chemicals into another
Mass and energy are conserved
Reactants  Products
2 kinds: energy releasing (exothermic) and energy absorbing (endothermic)

3. Exothermic Reactions
Reaction in which heat is given off (Ex. combustion of fuels)

4. Endothermic Reactions
Reaction in which heat is absorbed (Ex. water is evaporated)

5. Activation Energy
Energy needed to get a reaction going

6. Catalyst A substance that speeds up the rate of a reaction
It works by lowering activation energy

7. Enzymes Proteins that act as biological catalysts
They speed up chemical reactions that take place in cells
They are very specific and usually catalyze only one chemical reaction

8. Substrates The reactants of enzyme-catalyzed reactions
They bind to sites on the enzyme called active sites Lock and Key
CO2 + H2O  H2CO3
substrate

9. Regulation of Enzyme Activity
Temperature, pH, and regulatory molecules can affect how well enzymes work
Pepsin works best under acidic conditions (begins protein digestion)
Some are regulated by molecules that carry chemical signals within cells that turn enzymes “on” or “off”