MCAT Biochemistry Practice Questions
With Verified Study Solutions
a) by decreasing the E(a), enzymes increase both the reaction rate and the total amount
of product formed CORRECT ANSWERS Which of the following best describes the
function of enzymes?
a) by decreasing the E(a), enzymes increase both the reaction rate and the total amount
of product formed
b) by making the ∆G of the reaction more negative, enzymes increase the amount of
product formed per unit time
c) by decreasing the energy of the transition state, enzymes increase the amount of
product formed per unit time
d) by making the ∆G of the reaction more positive, enzymes increase the total amount
of product formed
a) C₄H₆O₅ CORRECT ANSWERS Malate dehydrogenase is a key enzyme in TCA
cycle, which catalyzes the following reaction, which is unfavorable under standard
conditions:
C₄H₆O₅ + NAD⁺→C₄H₄O₅ + NADH + H⁺
Which of the following corresponds to the compound that is most likely to be oxidized
under standard conditions?
a) C₄H₆O₅
b) NAD+
c) C₄H₄O₅
d) NADH
b) 3 only CORRECT ANSWERS All of the following are examples of oxidation-reduction
reactions EXCEPT:
1. C₃H₇O₆P + NAD⁺ + P₁→C₃H₈O₁₀P₂ + NADH + H⁺
2. C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
3. C₆H₁₄O₁₂P₂ → 2C₃H₇O₆P
a) 2 only
b) 3 only
c) 1 and 2 only
d) 1 and 3 only
a) the pKa will decrease due to favorable ionic interactions between the deprotonated
Glu and Lys residues CORRECT ANSWERS An acidic Glu residue in a protein (neutral
in its protonated form) has pKa value of 2.3 in the wild-type protein and is found near a
neutral Ile residue. What will be the effect of the pKa of the Glu residue if a mutation
substitutes a positively charged Lys residue for the Ile residue?
a) the pKa will decrease due to favorable ionic interactions between the deprotonated
Glu and Lys residues
, b) the pKa will decrease due to unfavorable ionic interactions between the deprotonated
Glu and Lys
c) the pKa will increase due to favorable ionic interactions between the deprotonated
Glu and Lys residues
d) the pKa will increase due to unfavorable ionic interactions between the deprotonated
Glu and Lys residues
c) Lys > Cys > Glu CORRECT ANSWERS Which of the following best orders the
relative basicity of the side chains of Glu (pKa=4.1), Cys (pKa=8.3), and Lys (pKa=10.8)
a) Cys > Glu > Lys
b) Lys > Glu > Cys
c) Lys > Cys > Glu
d) Glu > Cys > Lys
c) it would decrease CORRECT ANSWERS The cells in your body are constantly
undergoing cellular respiration, producing CO2 as a byproduct. What would happen to
the pH of your blood if you were to hold your breath?
a) it would increase
b) it would be the same
c) it would decrease
d) it cannot be determined with the information provided
d) the effect on ∆G cannot be determined without additional information CORRECT
ANSWERS If a mutation changed an Arg residue in the protein interior to a Leu residue,
what would be the likely effect on the ∆G of protein folding?
a) ∆G would become more positive
b) ∆G would become more negative
c) ∆G would remain unchanged
d) the effect on ∆G cannot be determined without additional information
b) Yes because the net effect would be a loss of active enzyme available for the
reaction CORRECT ANSWERS Some inhibitors bind irreversibly to enzymes by
covalent attachment. Would the kinetics seen under these conditions be similar to those
seen with a reversible noncompetitive inhibitor?
a) Yes because it would reduce the K(m) of the reaction
b) Yes because the net effect would be a loss of active enzyme available for the
reaction
c) No because if enough substrate binds to the active site the reaction will reach Vmax
d) No because K(m) will increase and Vmax will stay the same, similar to competitive
inhibition
b) a protease CORRECT ANSWERS Some enzymes can modify their substrate, and by
this means, regulate its activity. In many instances, these modifications are not
permanent since other enzymes can reverse them. Which of the following category of
enzymes will irreversibly modify their substrate?
a) a kinase
With Verified Study Solutions
a) by decreasing the E(a), enzymes increase both the reaction rate and the total amount
of product formed CORRECT ANSWERS Which of the following best describes the
function of enzymes?
a) by decreasing the E(a), enzymes increase both the reaction rate and the total amount
of product formed
b) by making the ∆G of the reaction more negative, enzymes increase the amount of
product formed per unit time
c) by decreasing the energy of the transition state, enzymes increase the amount of
product formed per unit time
d) by making the ∆G of the reaction more positive, enzymes increase the total amount
of product formed
a) C₄H₆O₅ CORRECT ANSWERS Malate dehydrogenase is a key enzyme in TCA
cycle, which catalyzes the following reaction, which is unfavorable under standard
conditions:
C₄H₆O₅ + NAD⁺→C₄H₄O₅ + NADH + H⁺
Which of the following corresponds to the compound that is most likely to be oxidized
under standard conditions?
a) C₄H₆O₅
b) NAD+
c) C₄H₄O₅
d) NADH
b) 3 only CORRECT ANSWERS All of the following are examples of oxidation-reduction
reactions EXCEPT:
1. C₃H₇O₆P + NAD⁺ + P₁→C₃H₈O₁₀P₂ + NADH + H⁺
2. C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
3. C₆H₁₄O₁₂P₂ → 2C₃H₇O₆P
a) 2 only
b) 3 only
c) 1 and 2 only
d) 1 and 3 only
a) the pKa will decrease due to favorable ionic interactions between the deprotonated
Glu and Lys residues CORRECT ANSWERS An acidic Glu residue in a protein (neutral
in its protonated form) has pKa value of 2.3 in the wild-type protein and is found near a
neutral Ile residue. What will be the effect of the pKa of the Glu residue if a mutation
substitutes a positively charged Lys residue for the Ile residue?
a) the pKa will decrease due to favorable ionic interactions between the deprotonated
Glu and Lys residues
, b) the pKa will decrease due to unfavorable ionic interactions between the deprotonated
Glu and Lys
c) the pKa will increase due to favorable ionic interactions between the deprotonated
Glu and Lys residues
d) the pKa will increase due to unfavorable ionic interactions between the deprotonated
Glu and Lys residues
c) Lys > Cys > Glu CORRECT ANSWERS Which of the following best orders the
relative basicity of the side chains of Glu (pKa=4.1), Cys (pKa=8.3), and Lys (pKa=10.8)
a) Cys > Glu > Lys
b) Lys > Glu > Cys
c) Lys > Cys > Glu
d) Glu > Cys > Lys
c) it would decrease CORRECT ANSWERS The cells in your body are constantly
undergoing cellular respiration, producing CO2 as a byproduct. What would happen to
the pH of your blood if you were to hold your breath?
a) it would increase
b) it would be the same
c) it would decrease
d) it cannot be determined with the information provided
d) the effect on ∆G cannot be determined without additional information CORRECT
ANSWERS If a mutation changed an Arg residue in the protein interior to a Leu residue,
what would be the likely effect on the ∆G of protein folding?
a) ∆G would become more positive
b) ∆G would become more negative
c) ∆G would remain unchanged
d) the effect on ∆G cannot be determined without additional information
b) Yes because the net effect would be a loss of active enzyme available for the
reaction CORRECT ANSWERS Some inhibitors bind irreversibly to enzymes by
covalent attachment. Would the kinetics seen under these conditions be similar to those
seen with a reversible noncompetitive inhibitor?
a) Yes because it would reduce the K(m) of the reaction
b) Yes because the net effect would be a loss of active enzyme available for the
reaction
c) No because if enough substrate binds to the active site the reaction will reach Vmax
d) No because K(m) will increase and Vmax will stay the same, similar to competitive
inhibition
b) a protease CORRECT ANSWERS Some enzymes can modify their substrate, and by
this means, regulate its activity. In many instances, these modifications are not
permanent since other enzymes can reverse them. Which of the following category of
enzymes will irreversibly modify their substrate?
a) a kinase
