Q: A biochemist is studying the conversion of glucose to glucose-6-phosphate. Which type of reaction is this, and what is the role of ATP?

Group transfer; ATP donates a phosphoryl group to glucose.

Q: Which of the following best explains why the hydrolysis of ATP is energetically favorable?

The products (ADP and Pi) are stabilized by resonance and solvation, and the release of electrostatic repulsion between phosphate groups.

Question 1

Which of the following best describes the role of ATP in group transfer reactions within metabolic pathways?

Accepted Answer

ATP provides energy via transfer of its phosphoryl group, often activating intermediates for subsequent reactions.

Question 2

Which bond in ATP is most commonly broken during energy-releasing reactions in cells?

Accepted Answer

The phosphoanhydride bond between the β- and γ-phosphates.

Question 3

Which of the following is a correct example of a group transfer reaction?

Accepted Answer

Transfer of a phosphoryl group from ATP to glucose to form glucose-6-phosphate.

Question 4

Which statement about the categories of biochemical reactions is TRUE?

Accepted Answer

Some reactions can belong to more than one category, such as group transfer and oxidation-reduction.

Question 5

In the reaction catalyzed by hexokinase during glycolysis, which molecule receives a phosphoryl group from ATP?

Accepted Answer

Glucose

Question 6

Which of the following is TRUE regarding NAD+ and FAD as redox cofactors?

Accepted Answer

Both NAD+ and FAD can accept two electrons, but FAD can also accept one electron at a time.

Question 7

Which formula correctly relates the standard free energy change ($\Delta G^{\circ'}$) to the standard reduction potentials ($E^{\circ'}$) of the acceptor and donor in a redox reaction?

Accepted Answer

$\Delta G^{\circ'} = -nF[E^{\circ'}_{acceptor} - E^{\circ'}_{donor}]$

Question 8

Given the following standard reduction potentials: $E^{\circ'}_{NAD^+/NADH} = -0.32\ V$ and $E^{\circ'}_{pyruvate/lactate} = -0.19\ V$, what is the direction of the reaction: pyruvate + NADH + $H^+ \rightarrow$ lactate + NAD+ under standard conditions?

Accepted Answer

The reaction favors lactate formation.

Question 9

Which of the following statements about hydrolysis reactions is CORRECT?

Accepted Answer

Hydrolysis reactions involve the addition of water to break a bond and are usually strongly favorable ($\Delta G^{\circ'} < 0$).

Question 10

Which molecule is typically used as an electron carrier in catabolic (oxidative) reactions?

Accepted Answer

NAD+

Question 11

A biochemist is studying the conversion of glucose to glucose-6-phosphate. Which type of reaction is this, and what is the role of ATP?

Accepted Answer

Group transfer; ATP donates a phosphoryl group to glucose.

Question 12

Which of the following best explains why the hydrolysis of ATP is energetically favorable?

Accepted Answer

The products (ADP and Pi) are stabilized by resonance and solvation, and the release of electrostatic repulsion between phosphate groups.

Question 13

Which equation is used to calculate the equilibrium constant ($K'_{eq}$) from the standard free energy change ($\Delta G^{\circ'}$)?

Accepted Answer

$K'_{eq} = e^{-\Delta G^{\circ'}/RT}$

Question 14

Which statement about the Nernst equation is correct?

Accepted Answer

It is used to calculate the reduction potential under non-standard conditions.

Question 15

Which of the following is TRUE about the difference between NAD+ and NADP+?

Accepted Answer

NAD+ is primarily used in catabolic reactions, while NADP+ is used in anabolic reactions.

Question 16

Which of the following reactions is an example of an oxidation-reduction reaction?

Accepted Answer

Conversion of lactate to pyruvate by lactate dehydrogenase.

Question 17

A scientist measures the standard reduction potential of two half-reactions: $E^{\circ'}_{A} = +0.50\ V$ and $E^{\circ'}_{B} = -0.20\ V$. Which compound will be reduced if A and B are mixed?

Accepted Answer

Compound A will be reduced because it has a higher (more positive) reduction potential.

Question 18

Which of the following is a correct statement about flavin cofactors (FAD/FMN)?

Accepted Answer

Flavin cofactors can participate in single electron transfers and are tightly bound to proteins.

Question 19

Which of the following best describes the function of glutamine synthetase in ATP-dependent reactions?

Accepted Answer

It catalyzes a two-step reaction where ATP activates glutamate, followed by addition of ammonia to form glutamine.

Group Transfer and Oxidation/Reduction Reactions in Biochemistry

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