©Themoon EXAM SOLUTIONS
25/11/2024 13:32PM
Workshop 2-BIOC 3021 Exam Questions
and Answers
Why does a plot of V vs S taper off and eventually reach a plateau at higher S levels? -
Answers✓✓- When S levels are high, the M-M plot actually approaches a limiting value of
Vmax.
- At high (S), where V approximates Vmax, virtually all of the enzyme active sites are occupied
by substrate.
- The addition of more S would not significantly increase the rate of reaction, because the rate
of reaction is limited by the total active sites available; once all the sites are filled, the reaction
can go no faster.
What is the Michaelis-Menten Equation? - Answers✓✓V = Vmax[S]/ [S] +km
The M-M Equation uses the terms (V), (Vmax), (S) and (Km). What do each of these terms
mean? - Answers✓✓V= observable velocity of the reaction. Tells us how rapidly product (p) is
being formed by the reaction.
Vmax = fastest reaction rate possible under the given assay conditions. Has dimensions of
change in product concentration per unit time.
S = substrate concentration
Km = Michaelis Constant. Has units of concentration
What does the Km term tell us about an enzyme? - Answers✓✓The Km tells us how efficient
enzymes are at low substrate levels
, ©Themoon EXAM SOLUTIONS
25/11/2024 13:32PM
What does it signify if an enzyme has a low Km or a high Km? - Answers✓✓- The Km tells us
how efficient enzymes are at low substrate levels?
- At low Km, the enzyme is very efficient at low substrate concentration. At high Km, enzymes
are inefficient at low substrate concentration.
What is the enzyme rate when the concentration of S = Km? - Answers✓✓1/2 Vmax.
Why is a V vs S plot linear at low S concentrations? - Answers✓✓The M-M equation reduces
to V = K[S] which is the equation for a straight line.
This is b/c when Km is much greater than [S], the [S] term can be dropped from the
denominator
Why does the plot curve off at intermediate S levels - Answers✓✓Because the whole M-M
equation is used to describe the rate of the reaction.
Why does V vs S plot plateau at high S levels? - Answers✓✓The M-M equation reduces to
V=Vmax. When S levels are high, the M-M plot approaches a limiting value of Vmax.
There is virtually no change in reaction rate once [S] is 10x greater than Km. The Km term can
be dropped from the equation.
What is the definition of turnover number and how does that constant relate to the Vmax of an
enzyme? - Answers✓✓Kcat = Vmax/[Et]
Gives the number of molecules of substrate that can be converted per second per molecule of
enzyme
25/11/2024 13:32PM
Workshop 2-BIOC 3021 Exam Questions
and Answers
Why does a plot of V vs S taper off and eventually reach a plateau at higher S levels? -
Answers✓✓- When S levels are high, the M-M plot actually approaches a limiting value of
Vmax.
- At high (S), where V approximates Vmax, virtually all of the enzyme active sites are occupied
by substrate.
- The addition of more S would not significantly increase the rate of reaction, because the rate
of reaction is limited by the total active sites available; once all the sites are filled, the reaction
can go no faster.
What is the Michaelis-Menten Equation? - Answers✓✓V = Vmax[S]/ [S] +km
The M-M Equation uses the terms (V), (Vmax), (S) and (Km). What do each of these terms
mean? - Answers✓✓V= observable velocity of the reaction. Tells us how rapidly product (p) is
being formed by the reaction.
Vmax = fastest reaction rate possible under the given assay conditions. Has dimensions of
change in product concentration per unit time.
S = substrate concentration
Km = Michaelis Constant. Has units of concentration
What does the Km term tell us about an enzyme? - Answers✓✓The Km tells us how efficient
enzymes are at low substrate levels
, ©Themoon EXAM SOLUTIONS
25/11/2024 13:32PM
What does it signify if an enzyme has a low Km or a high Km? - Answers✓✓- The Km tells us
how efficient enzymes are at low substrate levels?
- At low Km, the enzyme is very efficient at low substrate concentration. At high Km, enzymes
are inefficient at low substrate concentration.
What is the enzyme rate when the concentration of S = Km? - Answers✓✓1/2 Vmax.
Why is a V vs S plot linear at low S concentrations? - Answers✓✓The M-M equation reduces
to V = K[S] which is the equation for a straight line.
This is b/c when Km is much greater than [S], the [S] term can be dropped from the
denominator
Why does the plot curve off at intermediate S levels - Answers✓✓Because the whole M-M
equation is used to describe the rate of the reaction.
Why does V vs S plot plateau at high S levels? - Answers✓✓The M-M equation reduces to
V=Vmax. When S levels are high, the M-M plot approaches a limiting value of Vmax.
There is virtually no change in reaction rate once [S] is 10x greater than Km. The Km term can
be dropped from the equation.
What is the definition of turnover number and how does that constant relate to the Vmax of an
enzyme? - Answers✓✓Kcat = Vmax/[Et]
Gives the number of molecules of substrate that can be converted per second per molecule of
enzyme
