Chem 221 - Biochemistry for Science Majors » Fall 2021 » L9 Enzymes Part 2 of 3

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Question #1
An enzyme's KM describes the substrate concentration at which 100% of the enzyme's active sites are occupied by substrate.
A.   FALSE
B.   TRUE
Question #2
To be effective, enzymes must be present at the same concentration as their substrate
A.   FALSE
B.   TRUE
Question #3
Km has the dimensions of rate per second
A.   FALSE
B.   TRUE
Question #4
Km is equal to the substrate concentration that will bring the reaction to maximal velocity
A.   TRUE
B.   FALSE
Question #5
At very high substrate concentration, the velocity of the reaction is independent of the substrate concentration.
A.   FALSE
B.   TRUE
Question #6
Which of the following statements about allosteric enzymes is correct?
A.   Allosteric enzymes are usually single subunit enzymes.
B.   Allosteric enzymes display hyperbolic kinetics in response to changes in substrate concentration.
C.   Allosteric enzymes control metabolism.
D.   Allosteric enzymes display Michaelis-Menten kinetics.
Question #7
The higher is the Km, the lower is the affinity.
A.   TRUE
B.   FALSE
Question #8
Which of the following statements about Michaelis-Menten kinetics is correct?
A.   Km, the Michaelis constant, is expressed in terms of the reaction velocity.
B.   Km, the Michaelis constant, is defined as the dissociation constant of the enzyme-substrate complex.
C.   Km, the Michaelis constant, is a measure of the affinity the enzyme has for its substrate.
D.   Km, the Michaelis constant, is defined as the concentration of substrate required for the reaction to reach maximum velocity.
Question #9
The number of substrate molecules converted to product in a given unit of time by a single enzyme molecule at saturation is referred to as the:
A.   Michaelis-Menten number
B.   turnover number
C.   maximum velocity
D.   dissociation constant
E.   half-saturation constant
Question #10
The Lineweaver-Burk plot is used to:
A.   solve, graphically, for the rate of an enzymatic reaction at infinite substrate concentration
B.   solve, graphically, for the ratio of products to reactants for any starting substrate concentration
C.   extrapolate for the value of reaction rate at infinite enzyme concentration
D.   determine the equilibrium constant for an enzymatic reaction
E.   illustrate the effect of temperature on an enzymatic reaction
Question #11
Allosteric enzymes:
A.   usually have more than one polypeptide chain
B.   usually show strict Michaelis-Menten kinetics
C.   usually catalyze several different reactions within a metabolic pathway
D.   are regulated primarily by covalent modification
Question #12
Which of the following statements about Michaelis-Menten kinetics is correct?
A.   A low Michaelis constant (Km) indicates a high affinity of an enzyme for its substrate.
B.   The Michaelis constant (Km) of an enzyme increases when the enzyme concentration is increased.
C.   A high Michaelis constant (Km) indicates a high affinity of an enzyme for its substrate.
Question #13
Which of the following statements about Michaelis-Menten kinetics is correct?
A.   Michaelis-Menten kinetics assume the enzyme and substrate first bind to form an enzyme-substrate complex.
B.   Michaelis-Menten kinetics assume covalent binding occurs between enzyme and substrate
C.   Michaelis-Menten kinetics apply only to reaction rates before the product is formed.
Question #14
At high [S], [S] << KM and the KM term in the denominator of the MM equation becomes insignificant.
A.   TRUE
B.   FALSE
Question #15
Which of the following statements about enzyme kinetics is FALSE?
A.   Maximal activity of many human enzymes occurs around pH 7.4.
B.   Most enzymes operating in the human body work best at a temperature of 37°C.
C.   An enzyme–substrate complex can either form a product or dissociate back into the enzyme and substrate.
D.   An increase in the substrate concentration (at constant enzyme concentration) leads to proportional increases in the rate of the reaction.
Question #16
To calculate the turnover number of an enzyme you need to know the:
A.   KM for the substrate
B.   initial velocity of the catalyzed reaction at [S] >> KM
C.   enzyme concentration
D.   initial velocity of the catalyzed reaction at low [S]
E.   two of these
Question #17
Vmax is an important characteristic of enzyme–substrate interactions and is independent of enzyme and substrate concentrations.
A.   TRUE
B.   FALSE
Question #18
Vmax is found on the X coordinate.
A.   FALSE
B.   TRUE
Question #19
Which of the following kinetic parameters remains the same for S --> P, whether the reaction is enzyme-catalyzed or uncatalyzed?
A.   Vo
B.   Keq
Question #20
Allosteric enzymes are cooperative.
A.   FALSE
B.   TRUE
Question #21
Allosteric enzymes do not obey the Michaelis-Menten kinetics (sigmoidal curve) but instead have hyperbolic kinetics.
A.   TRUE
B.   FALSE
Question #22
V0 is called initial velocity.
A.   FALSE
B.   TRUE
Question #23
The Lineweaver-Burk plot is especially useful when determining the type of inhibition that an enzyme is experiencing because the Vmax and Km can be compared without estimation.
A.   FALSE
B.   TRUE
Question #24
Km is found on the Y axis.
A.   FALSE
B.   TRUE
Question #25
At high [S],  when [S] >> KM, the enzyme's active site are saturated with the substrate.
A.   TRUE
B.   FALSE
Question #26
The rate of formation of product in an enzymatically catalyzed reaction is called V0.
A.   TRUE
B.   FALSE
Question #27
The KM can vary greatly from enzyme to enzyme, and even for different substrates of the same enzyme.
A.   FALSE
B.   TRUE
Question #28
KM is measured in mol/sec.
A.   TRUE
B.   FALSE
Question #29
The further away from zero (the more positive) the Km is, the higher is the affinity.
A.   TRUE
B.   FALSE
Question #30
The "blue enzyme" has higher Km than the "red enzyme"
A.   FALSE
B.   TRUE
Question #31
Kcat is also called turnover number.
A.   TRUE
B.   FALSE
Question #32
Vmax depends on the concentration of the enzyme.
A.   FALSE
B.   TRUE
Question #33
The units of KM are the same of the units of  [S].
A.   TRUE
B.   FALSE
Question #34
Km is the Menten constant.
A.   TRUE
B.   FALSE
Question #35
The Michaelis-Menten Equation is the equation of a parabolic curve.
A.   FALSE
B.   TRUE
Question #36
The maximal rate, Vmax, is attained when 50% of the catalytic sites on the enzyme are saturated with substrate.
A.   TRUE
B.   FALSE
Question #37
Michaelis and Menten proposed that formation of an enzyme-substrate complex (ES) is a necessary intermediate, a necessary step, in the catalyzed reaction.
A.   FALSE
B.   TRUE
Question #38
An enzyme kinetic experiment is one in which the amount of the substrate is kept constant and the enzyme concentration is gradually increased.
A.   FALSE
B.   TRUE
Question #39
At low [S], V0 becomes virtually independent of [S] and approaches a maximal limit.
A.   FALSE
B.   TRUE
Question #40
For a unimolecular noncatalyzed reaction (first order), a plot of the reaction rate as a function of the concentration of reactant yields a straight line.
A.   FALSE
B.   TRUE
Question #41
The rate of formation of product in an enzymatically catalyzed reaction is called Vmax.
A.   FALSE
B.   TRUE
Question #42
KM is the number of moles of product formed in a unit time. 
A.   FALSE
B.   TRUE
Question #43
The rate of formation of product in an enzymatically catalyzed reaction is called initial velocity.
A.   TRUE
B.   FALSE
Question #44
V0 is the number of moles of product formed in a unit time. 
A.   TRUE
B.   FALSE
Question #45
Vmax is the number of moles of product formed in a unit time. 
A.   TRUE
B.   FALSE
Question #46
KM is an important characteristic of enzyme–substrate interactions and is dependent of enzyme and substrate concentrations.
A.   FALSE
B.   TRUE
Question #47
Kcat depends on the concentration of enzyme.
A.   FALSE
B.   TRUE
Question #48
  
A.   TRUE
B.   FALSE

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