Download 20.3 Factors Affecting Enzyme 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.
• pH.
• concentration of the enzyme
and substrate.
Learning Goal Describe the effect
of changes of temperature, pH,
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.
pH and Enzyme Activity
Enzymes
• are most active at optimum
pH, where proper tertiary
structure of the protein is
maintained.
• contain R groups of amino
acids with proper charges at
optimum pH.
• lose activity in low or high pH
as tertiary structure is
disrupted.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Optimum pH Values
Enzymes in
• the body have an optimum pH of about 7.4.
• certain organs operate at lower or higher optimum
pH 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 pH of 6.2.
Determine the effect of the following on its rate of reaction:
A. increasing the concentration of sucrase
B. changing the pH 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 pH 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 pH 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.