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Biochem Midterm #2 Questions with Correct
Answers | Updated (100% Correct Answers)
Which of the following statements about the oxyanion hole is NOT
true?
a.) The backbone NH bonds of S195 and G193 create H-bonding
interactions with the developing negative charge as Ser 195 attacks
the scissile carbon bond.
b.) It represents an electrostatic interaction that leads to a lower
energy state.
c.) It represents an enthalpic interaction that helps stabilize the
transition state.
d.) This preformed loop is properly positioned to stabilize the
negatively charged tetrahedral intermediate involved in amide bond
hydrolysis. Answer: d.) This preformed loop is properly positioned
to stabilize the negatively charged tetrahedral intermediate involved
in amide bond hydrolysis.
In an enzyme-catalyzed reaction, the lifetime of the transition state
is similar to the vibrational frequencies of covalent bonds. True or
false? Answer: True
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,2
Which of the following describes a mechanism that enzymes use to
achieve their rate enhancement of reactions?
a.) distortion of the substrate or active site, which, in effect, lowers
the energy of activation
b.) preferential binding to the transition state through
complementary non-covalent interactions
c.) altering the reaction pathway to include intermediate states
d.) All of the listed choices describe mechanisms used by enzymes
to achieve their rate enhancement of reactions. Answer: d.) All of
the listed choices describe mechanisms used by enzymes to achieve
their rate enhancement of reactions
Match each cofactor with its function:
1. thiamine pyrophosphate
2. coenzyme A
3. Biotin
4. NAD+
a. CO2 activation/transfer
b. oxidation.reduction
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c. activation of aldehydes
d. acyl group transfer Answer: thiamine pyrophosphate - activation
of aldehydes
coenzyme A - acyl group transfer
Biotin - CO2 activation.transfer
NAD+ - oxidation/reduction
The cofactor NAD+ is:
a. able to accept 2 electrons and 2 protons.
b. an oxidant.
c. a reductant.
d. oxidized to NADH/H+ in dehydrogenase reactions.
e. covalently linked to enzymes in whose catalytic activity it assists.
Answer: b. an oxidant.
Which of the following amino acid residues are often involved in
proton transfers in enzyme-catalyzed reactions?
a. Glutamine, asparagine, lysine, and tyrosine
b. Histidine, aspartate, lysine, and serine
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, 4
c. Histidine, aspartate, serine, and cysteine
d. Histidine, aspartate, glutamate, arginine, and lysine
e. Serine, tyrosine, arginine, and cysteine Answer: d. Histidine,
aspartate, glutamate, arginine, and lysine
Catalysts affect the thermodynamic of a chemical reaction. True or
false? Answer: False.
A second-order reaction:
a. only occurs in multistep processes.
b. has a rate constant with units of (time)-1.
c. occurs when one substrate is converted into one product.
d. is characterized by two molecules coming together to form a
product.
e. is the rate-limiting step of a reaction. Answer: d. is characterized
by two molecules coming together to form a product.
Consider the following reaction: A --> B
which of the following statements about this reaction are correct?
1.) If you double the concentration of the reagent A, you will double
the rate
© 2025 All rights reserved
Biochem Midterm #2 Questions with Correct
Answers | Updated (100% Correct Answers)
Which of the following statements about the oxyanion hole is NOT
true?
a.) The backbone NH bonds of S195 and G193 create H-bonding
interactions with the developing negative charge as Ser 195 attacks
the scissile carbon bond.
b.) It represents an electrostatic interaction that leads to a lower
energy state.
c.) It represents an enthalpic interaction that helps stabilize the
transition state.
d.) This preformed loop is properly positioned to stabilize the
negatively charged tetrahedral intermediate involved in amide bond
hydrolysis. Answer: d.) This preformed loop is properly positioned
to stabilize the negatively charged tetrahedral intermediate involved
in amide bond hydrolysis.
In an enzyme-catalyzed reaction, the lifetime of the transition state
is similar to the vibrational frequencies of covalent bonds. True or
false? Answer: True
© 2025 All rights reserved
,2
Which of the following describes a mechanism that enzymes use to
achieve their rate enhancement of reactions?
a.) distortion of the substrate or active site, which, in effect, lowers
the energy of activation
b.) preferential binding to the transition state through
complementary non-covalent interactions
c.) altering the reaction pathway to include intermediate states
d.) All of the listed choices describe mechanisms used by enzymes
to achieve their rate enhancement of reactions. Answer: d.) All of
the listed choices describe mechanisms used by enzymes to achieve
their rate enhancement of reactions
Match each cofactor with its function:
1. thiamine pyrophosphate
2. coenzyme A
3. Biotin
4. NAD+
a. CO2 activation/transfer
b. oxidation.reduction
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,3
c. activation of aldehydes
d. acyl group transfer Answer: thiamine pyrophosphate - activation
of aldehydes
coenzyme A - acyl group transfer
Biotin - CO2 activation.transfer
NAD+ - oxidation/reduction
The cofactor NAD+ is:
a. able to accept 2 electrons and 2 protons.
b. an oxidant.
c. a reductant.
d. oxidized to NADH/H+ in dehydrogenase reactions.
e. covalently linked to enzymes in whose catalytic activity it assists.
Answer: b. an oxidant.
Which of the following amino acid residues are often involved in
proton transfers in enzyme-catalyzed reactions?
a. Glutamine, asparagine, lysine, and tyrosine
b. Histidine, aspartate, lysine, and serine
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, 4
c. Histidine, aspartate, serine, and cysteine
d. Histidine, aspartate, glutamate, arginine, and lysine
e. Serine, tyrosine, arginine, and cysteine Answer: d. Histidine,
aspartate, glutamate, arginine, and lysine
Catalysts affect the thermodynamic of a chemical reaction. True or
false? Answer: False.
A second-order reaction:
a. only occurs in multistep processes.
b. has a rate constant with units of (time)-1.
c. occurs when one substrate is converted into one product.
d. is characterized by two molecules coming together to form a
product.
e. is the rate-limiting step of a reaction. Answer: d. is characterized
by two molecules coming together to form a product.
Consider the following reaction: A --> B
which of the following statements about this reaction are correct?
1.) If you double the concentration of the reagent A, you will double
the rate
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