1 Look up the definitions to these terms: Enzyme Enzyme Substrate/ Reactant Substrate/ Reactant Product Product Reaction Reaction Active site Active site

2 Enzymes Enzymes Catalysts for biological reactions Catalysts for biological reactions Most are proteins Most are proteins Lower the energy necessary for reaction to happen (activation energy) Lower the energy necessary for reaction to happen (activation energy)

3 Enzymes, cont. Increase the rate of reaction Increase the rate of reaction Activity lost if denatured Activity lost if denatured May contain cofactors such as metal ions or organic (vitamins) May contain cofactors such as metal ions or organic (vitamins)

4 Names of Enzymes Often end in –ase: Often end in –ase: Ex: sucrase – acts on sucrose lipase - acts on lipid lipase - acts on lipid Common names of digestion enzymes still use –in Common names of digestion enzymes still use –in Ex: pepsin, trypsin

5 Enzyme Action: Lock and Key Model Substrate= reactant or substance to be changed 1. Enzyme binds substrate in region called the active site Only specific substrates can fit the active site Only specific substrates can fit the active site 2. Enzyme-substrate complex forms 3. Substrate reacts to form product 4. Product is released 5. Go back to step 1- bind new substrate

6 Lock and Key Model E = enzyme S = substrate P = product Active site E + S ES complex E + P E + S ES complex E + P S P P S

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9 Enzyme Animation port.com/ /lib/ /Animations/Enzyme_activity.html port.com/ /lib/ /Animations/Enzyme_activity.html port.com/ /lib/ /Animations/Enzyme_activity.html port.com/ /lib/ /Animations/Enzyme_activity.html

10 Learning Check A. The active site is (1) the enzyme (2) a section of the enzyme (3) the substrate B. The substance to be changed by the enzyme is the (1) Substrate (2) Product

11 Solution A. The active site is (2) a section of the enzyme B. The substance to be changed by the enzyme is the (1) Substrate

12 Factors Affecting Enzyme Action I. 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 Activity lost with denaturation at high temperatures at high temperatures

13 Affect of Temperature on Enzyme Action Optimum temperature ReactionRateofEnzyme Low High Low High Temperature Temperature

14 Factors Affecting Enzyme Action II. 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

15 Affect of Substrate Concentration on Enzyme Action Maximum activity ReactionRate substrate concentration substrate concentration

16 Factors Affecting Enzyme Action III. pH Most lose activity in low or high pH Most lose activity in low or high pH Function best with Narrow range of pH Function best with Narrow range of pH Necessary for correct tertiary structure of enzyme Necessary for correct tertiary structure of enzyme

17 Factors Affecting Enzyme Action ReactionRate Optimum pH pH

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20 Quiz Yourself: Sucrase has an optimum temperature of 37°C and an optimum pH of 6.2. Determine the effect of the following on its rate of reaction (1) no change (2) increase (3) decrease A. Increasing the concentration of sucrose B. Changing the pH to 4 C. Running the reaction at 70°C

21 Solution Sucrase has an optimum temperature of 37°C and an optimum pH of 6.2. Determine the effect of the following on its rate of reaction (1) no change (2) increase (3) decrease A. 2, 1 Increasing the concentration of sucrose B. 3 Changing the pH to 4 C. 3 Running the reaction at 70°C