Chemical Reactions and Enzymes Bio- Chapter 2 section 4 Chemical Reactions and Enzymes What are they? How do they work? Use your Cornell Notes

Chemical Reactions Chemical reaction = process that changes one set of chemicals into another Beginning chemicals = reactants Ending chemicals = products Reactants  Products CO2 + H2O  H2CO3 Chemical reactions always rearrange chemical bonds

Energy in Reactions Chemical reactions that release energy can happen spontaneously (no help needed) (exothermic) Chemical reactions that absorb energy will not occur without “activation energy” (endothermic) Activation energy – energy required to start a reaction Only needed at the start

Activation Energy

Enzymes Catalyst = a substance that speeds up the rate of a chemical reaction Catalysts work by lowering the activation energy required for the reaction Enzymes = proteins that act as catalysts Enzymes speed up chemical reactions in cells Enzymes are very specific

Enzymes lower activation energy

Enzyme Action Enzymes provide a site where reactants can be brought together to react Reactants at an enzyme site = substrates The site on the enzyme = active site Combination of enzyme and substrates = enzyme-substrate complex The shape of the active site is specific to a substrate

The active site is shape specific for a certain substrate enzyme action

Some specific enzymes Breaks down Starch in mouth and small intestine Breaks down protein in stomach Breaks down lipids in small intestine Breaks down milk sugar (lactose) Amylase Peptin Lipase Lactase