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.   TRUE
B.   FALSE
Question #2
To be effective, enzymes must be present at the same concentration as their substrate
A.   TRUE
B.   FALSE
Question #3
Km has the dimensions of rate per second
A.   TRUE
B.   FALSE
Question #4
Km is equal to the substrate concentration that will bring the reaction to maximal velocity
A.   FALSE
B.   TRUE
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 control metabolism.
B.   Allosteric enzymes are usually single subunit enzymes.
C.   Allosteric enzymes display hyperbolic kinetics in response to changes in substrate concentration.
D.   Allosteric enzymes display Michaelis-Menten kinetics.
Question #7
The higher is the Km, the lower is the affinity.
A.   FALSE
B.   TRUE
Question #8
Which of the following statements about Michaelis-Menten kinetics is correct?
A.   Km, the Michaelis constant, is defined as the concentration of substrate required for the reaction to reach maximum velocity.
B.   Km, the Michaelis constant, is expressed in terms of the reaction velocity.
C.   Km, the Michaelis constant, is defined as the dissociation constant of the enzyme-substrate complex.
D.   Km, the Michaelis constant, is a measure of the affinity the enzyme has for its substrate.
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.   maximum velocity
B.   half-saturation constant
C.   dissociation constant
D.   Michaelis-Menten number
E.   turnover number
Question #10
The Lineweaver-Burk plot is used to:
A.   solve, graphically, for the ratio of products to reactants for any starting substrate concentration
B.   determine the equilibrium constant for an enzymatic reaction
C.   illustrate the effect of temperature on an enzymatic reaction
D.   solve, graphically, for the rate of an enzymatic reaction at infinite substrate concentration
E.   extrapolate for the value of reaction rate at infinite enzyme concentration
Question #11
Allosteric enzymes:
A.   are regulated primarily by covalent modification
B.   usually catalyze several different reactions within a metabolic pathway
C.   usually have more than one polypeptide chain
D.   usually show strict Michaelis-Menten kinetics
Question #12
Which of the following statements about Michaelis-Menten kinetics is correct?
A.   The Michaelis constant (Km) of an enzyme increases when the enzyme concentration is increased.
B.   A high Michaelis constant (Km) indicates a high affinity of an enzyme for its substrate.
C.   A low 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 apply only to reaction rates before the product is formed.
B.   Michaelis-Menten kinetics assume the enzyme and substrate first bind to form an enzyme-substrate complex.
C.   Michaelis-Menten kinetics assume covalent binding occurs between enzyme and substrate
Question #14
At high [S], [S] << KM and the KM term in the denominator of the MM equation becomes insignificant.
A.   FALSE
B.   TRUE
Question #15
Which of the following statements about enzyme kinetics is FALSE?
A.   An increase in the substrate concentration (at constant enzyme concentration) leads to proportional increases in the rate of the reaction.
B.   An enzyme–substrate complex can either form a product or dissociate back into the enzyme and substrate.
C.   Most enzymes operating in the human body work best at a temperature of 37°C.
D.   Maximal activity of many human enzymes occurs around pH 7.4.
Question #16
To calculate the turnover number of an enzyme you need to know the:
A.   enzyme concentration
B.   initial velocity of the catalyzed reaction at low [S]
C.   initial velocity of the catalyzed reaction at [S] >> KM
D.   two of these
E.   KM for the substrate
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.   TRUE
B.   FALSE
Question #19
Which of the following kinetic parameters remains the same for S --> P, whether the reaction is enzyme-catalyzed or uncatalyzed?
A.   Keq
B.   Vo
Question #20
Allosteric enzymes are cooperative.
A.   TRUE
B.   FALSE
Question #21
Allosteric enzymes do not obey the Michaelis-Menten kinetics (sigmoidal curve) but instead have hyperbolic kinetics.
A.   FALSE
B.   TRUE
Question #22
V0 is called initial velocity.
A.   TRUE
B.   FALSE
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.   TRUE
B.   FALSE
Question #24
Km is found on the Y axis.
A.   TRUE
B.   FALSE
Question #25
At high [S],  when [S] >> KM, the enzyme's active site are saturated with the substrate.
A.   FALSE
B.   TRUE
Question #26
The rate of formation of product in an enzymatically catalyzed reaction is called V0.
A.   FALSE
B.   TRUE
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.   FALSE
B.   TRUE
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.   FALSE
B.   TRUE
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.   FALSE
B.   TRUE
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.   TRUE
B.   FALSE
Question #39
At low [S], V0 becomes virtually independent of [S] and approaches a maximal limit.
A.   TRUE
B.   FALSE
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.   TRUE
B.   FALSE
Question #42
KM is the number of moles of product formed in a unit time. 
A.   TRUE
B.   FALSE
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.   TRUE
B.   FALSE
Question #47
Kcat depends on the concentration of enzyme.
A.   FALSE
B.   TRUE
Question #48
  
A.   FALSE
B.   TRUE

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