1 Enzymes Enzymes Factors Affecting Enzyme Action

2 Enzymes Catalyst (substances which make chemical reactions go faster) for biological reactions Catalyst (substances which make chemical reactions go faster) for biological reactions Over 4000 biochemical reactions Over 4000 biochemical reactions Most are proteins Most are proteins Increase the rate of reaction Increase the rate of reaction Activity lost if denatured (structure change) Activity lost if denatured (structure change) May be simple proteins May be simple proteins

3 Name of Enzymes End in –ase End in –ase Identifies a reacting substance Identifies a reacting substance sucrase – reacts sucrose lipase - reacts lipid Describes function of enzyme Describes function of enzyme oxidase – catalyzes oxidation hydrolase – catalyzes hydrolysis Common names of digestion enzymes still use –in Common names of digestion enzymes still use –in pepsin, trypsin

4 Enzyme Action: Lock and Key Model An enzyme binds a substrate in a region called the active site An enzyme binds a substrate in a region called the active site Only certain substrates can fit the active site Only certain substrates can fit the active site Amino acid (R groups) in the active site help substrate bind Amino acid (R groups) in the active site help substrate bind Enzyme-substrate complex forms Enzyme-substrate complex forms Substrate reacts to form product Substrate reacts to form product Product is released Product is released

5 Lock and Key Model E + S ES complex E + P E + S ES complex E + P S P P S

6 Factors Affecting Enzyme Action: Temperature Little activity at low temperature Little activity at low temperature Rate increases with temperature Rate increases with temperature Most active at optimum temperatures (usually 37°C in humans) Most active at optimum temperatures (usually 37°C in humans) Activity lost with denaturation at high temperatures Activity lost with denaturation at high temperatures

7 Factors Affecting Enzyme Action Optimum temperature ReactionRate Low High Low High Temperature Temperature

8 Factors Affecting Enzyme Action: Substrate Concentration Increasing substrate concentration increases the rate of reaction (enzyme concentration is constant) Increasing substrate concentration increases the rate of reaction (enzyme concentration is constant) Maximum activity reached when all of enzyme combines with substrate Maximum activity reached when all of enzyme combines with substrate

9 Factors Affecting Enzyme Action Maximum activity ReactionRate substrate concentration substrate concentration

10 Factors Affecting Enzyme Action: pH Maximum activity at optimum pH Maximum activity at optimum pH Narrow range of activity Narrow range of activity Most lose activity in low or high pH Most lose activity in low or high pH

11 Factors Affecting Enzyme Action ReactionRate Optimum pH pH