Enzymes

UNIT 5: ENZYMES


Biological catalyst: a substance that increases the rate of a chemical reaction and
is not changed by the reaction
Enzyme: proteins that function as biological catalysts
 Important in all living organisms in terms of reaction speed necessary to sustain
life
 Can be used over and over again
 Made inactive by high temperature
 Work best at a particular temperature and a particular pH
 Specific
Enzyme Substrate Product
Protease Protein Amino acids
 Pepsin
Catalase Hydrogen peroxide Water and hydrogen
Carbohydrase Carbohydrate
 Amylase  Starch  Maltose
 Maltase  Maltose  Glucose
 Sucrase  Sucrose
 Starch phosphorylase  Build up glucose  Starch
Lipase Lipid Fatty acids and
glycerol

Substrate: substance which is present at the beginning of reaction in an enzyme-
controlled reaction
Product: substance made by the reaction
Active site: a shape that is complementary to the shape of part of the substrate
Enzyme-substrate complex: the substrate fits into the enzyme
 Each enzyme can only act on a particular kind of substrate
 The substrate fits into the active site of enzyme, forming an enzyme-substrate
complex because they have complementary shapes. When the substrate is in
the active site, the enzyme breaks it apart

Temperature and enzyme activity:
 Happen faster at higher temperature because molecules have more kinetic
energy, bump into other molecules more frequently
 Denatured by high temperature (active site no longer fits perfectly with the
substrate)
 Work fastest at optimum temperature

pH and enzyme activity:
 If pH becomes very acidic or alkaline, enzymes are denatured
 Enzyme’s optimum pH depends on the environment it is in (protease –pH 2
because there is HCl in the stoma