 Enzymes – are protein substances that are necessary for most of the chemical reactions that occur in living cells  Enzymes affect the rate or speed of a reaction.

 Usually end in –ase  Derived from the name of the substrate Ex. Maltase splits maltose into 2 glucose molecules Enzymes that break down: proteins = proteases lipids = lipases

 Catalyst – a substance that brings about a reaction without being changed itself Is an enzyme a catalyst? YES

 Substrate – the substance that an enzyme acts upon

 Active site – the region on the surface of an enzyme where the substrate molecules attach  The active site is located on the enzyme

 Enzyme-substrate complex – when the substrate molecule comes in contact with the active site of an enzyme The enzyme-substrate complex is temporary.

 The Lock and Key Model – is a theory that explains how the enzyme and substrate fit together  Each substrate can only fit into specific enzymes

 Induced-Fit Model – the theory in which the enzyme slightly changes shape to allow the substrate to fit the active site of the enzyme

1. Small amounts of an enzyme can cause the reaction of large quantities of substrate. 2. Enzymes work best at certain temperatures. 3. Enzymes work best at a certain pH. 4. The rate of reaction depends on the concentrations of the enzyme and the substrate. 5. Sometimes enzymes need a coenzyme to function.

 Denaturation – is when high temperatures cause the shape of the enzyme to change, so the active site no longer fits the substrate

 Coenzyme – allows an enzyme to perform its function Example of a coenzyme: a vitamin