20 3 Factors Affecting Enzyme Activity The activity

20. 3 Factors Affecting Enzyme Activity The activity of an enzyme describes how fast an enzyme catalyzes the reaction and is strongly affected by reaction conditions, such as • temperature. • p. H. • concentration of the enzyme and substrate. Learning Goal Describe the effect of changes of temperature, p. H, concentration of enzyme, and concentration of substrate on enzyme activity. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake Thermophiles survive in the high temperatures (50°C to 120°C) of a hot spring. © 2016 Pearson Education, Inc.

Temperature and Enzyme Activity Enzymes • are most active at an optimum temperature (usually 37°C in humans). • show little activity at low temperatures. • lose activity at high temperatures as denaturation occurs. Core Chemistry Skill Identifying Factors Affecting Enzyme Activity General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Temperature and Enzyme Activity Thermophiles • live in environments where temperatures range from 50°C to 120°C. • have enzymes with tertiary structures that are not destroyed by such high temperatures. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

p. H and Enzyme Activity Enzymes • are most active at optimum p. H, where proper tertiary structure of the protein is maintained. • contain R groups of amino acids with proper charges at optimum p. H. • lose activity in low or high p. H as tertiary structure is disrupted. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Optimum p. H Values Enzymes in • the body have an optimum p. H of about 7. 4. • certain organs operate at lower or higher optimum p. H values. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Enzyme Concentration An increase in enzyme concentration • increases the rate of reaction (at constant substrate concentration). • binds more substrate with enzyme. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Substrate Concentration An increase in substrate concentration • increases the rate of reaction (at constant enzyme concentration). • eventually saturates an enzyme with substrate to give maximum activity. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Study Check Sucrase has an optimum temperature of 37°C and an optimum p. H of 6. 2. Determine the effect of the following on its rate of reaction: A. increasing the concentration of sucrase B. changing the p. H to 4. 0 C. running the reaction at 70°C 1) no change 2) increase General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake 3) decrease © 2016 Pearson Education, Inc.

Solution Sucrase has an optimum temperature of 37°C and an optimum p. H of 6. 2. Determine the effect of the following on its rate of reaction: A. increasing the concentration of sucrase 2) increase B. changing the p. H to 4. 0 3) decrease C. running the reaction at 70°C 3) decrease 1) no change 2) increase General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake 3) decrease © 2016 Pearson Education, Inc.