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Look up the definitions to these terms:

Learn about enzymes as catalysts in biological reactions, their structure, function, and factors affecting their activity like temperature, substrate concentration, and pH.

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Look up the definitions to these terms:

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

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

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

  4. Names of Enzymes • Often end in –ase: Ex: sucrase – acts on sucrose lipase - acts on lipid • 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 • Enzyme binds substrate in region called the active site • Only specific substrates can fit the active site • Enzyme-substrate complex forms • Substrate reacts to form product • 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 P S S P

  7. Enzyme Animation • http://www.lew-port.com/10712041113402793/lib/10712041113402793/Animations/Enzyme_activity.html

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

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

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

  11. Affect of Temperature on Enzyme Action Optimum temperature Reaction Rate of Enzyme Low High Temperature

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

  13. Affect of Substrate Concentration on Enzyme Action Maximum activity Reaction Rate substrate concentration

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

  15. Factors Affecting Enzyme Action Reaction Rate Optimum pH 3 5 7 9 11 pH

  16. 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

  17. 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

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