Question 1

Which statement is FALSE regarding carbonyl groups?

Accepted Answer

A)  The carbon atom in a carbonyl group is more oxidized than the carbon atom in carbon dioxide. 
B)  The carbon atom of a carbonyl group is an electrophile. 
C)  Electron delocalization by a carbonyl group stabilizes an adjoining carbanion, thus facilitating its formation. 
D)  Positively charged metal ions may enhance the ability of a carbonyl group to act as an electron sink. 
E)  The functional group of aldehydes and ketones is a carbonyl group. 
A)  The carbon atom in a carbonyl group is more oxidized than the carbon atom in carbon dioxide. 
B)  The carbon atom of a carbonyl group is an electrophile. 
C)  Electron delocalization by a carbonyl group stabilizes an adjoining carbanion, thus facilitating its formation. 
D)  Positively charged metal ions may enhance the ability of a carbonyl group to act as an electron sink. 
E)  The functional group of aldehydes and ketones is a carbonyl group.

Question 2

Which factor does NOT contribute to the large, negative, free-energy change upon hydrolysis of "high-energy" compounds?

Accepted Answer

A)  electrostatic repulsion in the reactant 
B)  low activation energy of forward reaction 
C)  stabilization of products by extra resonance forms 
D)  stabilization of products by ionization 
E)  stabilization of products by solvation 
A)  electrostatic repulsion in the reactant 
B)  low activation energy of forward reaction 
C)  stabilization of products by extra resonance forms 
D)  stabilization of products by ionization 
E)  stabilization of products by solvation

Question 3

The reaction A + B $\rightarrow$C has a $\Delta$G'° of -20 kJ/mol at 25° C. Starting under standard conditions, one can predict that:

Accepted Answer

A)  at equilibrium, the concentration of B will exceed the concentration of A. 
B)  at equilibrium, the concentration of C will be less than the concentration of A. 
C)  at equilibrium, the concentration of C will be much greater than the concentration of A or B. 
D)  C will rapidly break down to A + B. 
E)  when A and B are mixed, the reaction will proceed rapidly toward formation of C. 
A)  at equilibrium, the concentration of B will exceed the concentration of A. 
B)  at equilibrium, the concentration of C will be less than the concentration of A. 
C)  at equilibrium, the concentration of C will be much greater than the concentration of A or B. 
D)  C will rapidly break down to A + B. 
E)  when A and B are mixed, the reaction will proceed rapidly toward formation of C.

Question 4

The reaction ATP $\rightarrow$ ADP + Pi is an example of a(n) _____ reaction.

Accepted Answer

A)  homolytic cleavage 
B)  internal rearrangement 
C)  free radical 
D)  group transfer 
E)  oxidation/reduction 
A)  homolytic cleavage 
B)  internal rearrangement 
C)  free radical 
D)  group transfer 
E)  oxidation/reduction

Question 5

The hydrolysis of ATP has a large negative $\Delta$G'°; nevertheless it is stable in solution due to:

Accepted Answer

A)  entropy stabilization. 
B)  ionization of the phosphates. 
C)  resonance stabilization. 
D)  the hydrolysis reaction being endergonic. 
E)  the hydrolysis reaction having a large activation energy. 
A)  entropy stabilization. 
B)  ionization of the phosphates. 
C)  resonance stabilization. 
D)  the hydrolysis reaction being endergonic. 
E)  the hydrolysis reaction having a large activation energy.

Question 6

The standard free-energy changes for the reactions below are given. phosphocreatine $\rightarrow$  creatine + Pi
$\Delta$G'° = -43.0 kJ/mol
ATP $\rightarrow$  ADP + Pi
$\Delta$G'° = -30.5 kJ/mol
What is the overall $\Delta$G'° for the following reaction?
Phosphocreatine + ADP$\rightarrow$ creatine + ATP

Accepted Answer

A)  -73.5 kJ/mol 
B)  -12.5 kJ/mol 
C)  +12.5 kJ/mol 
D)  +73.5 kJ/mol 
E)  $\Delta$G'° cannot be calculated without Keq'. 
A)  -73.5 kJ/mol 
B)  -12.5 kJ/mol 
C)  +12.5 kJ/mol 
D)  +73.5 kJ/mol 
E)  $\Delta$G'° cannot be calculated without Keq'.

Question 7

Consider the reaction: A + B$\rightarrow$ C + D. If the equilibrium constant for this reaction is a large number (say, 10,000), what do we know about the standard free-energy change ($\Delta$G'°) for the reaction? Describe the relationship between Keq' and $\Delta$G'°.

Accepted Answer

If the equilibrium constant (K_eq) for t

Question 8

Hydrolysis of 1 M glucose 6-phosphate catalyzed by glucose 6-phosphatase is 99% complete at equilibrium (i.e., only 1% of the substrate remains). Which statement is MOST nearly correct? (R = 8.315 J/mol · K; T = 298 K)

Accepted Answer

A)  $\Delta$G'° is -11 kJ/mol. 
B)  $\Delta$G'° is -5 kJ/mol. 
C)  $\Delta$G'° is 0 kJ/mol. 
D)  $\Delta$G'° is +11 kJ/mol. 
E)  $\Delta$G'° cannot be determined from the information given. 
A)  $\Delta$G'° is -11 kJ/mol. 
B)  $\Delta$G'° is -5 kJ/mol. 
C)  $\Delta$G'° is 0 kJ/mol. 
D)  $\Delta$G'° is +11 kJ/mol. 
E)  $\Delta$G'° cannot be determined from the information given.

Question 9

The structure of NAD+ does NOT include:

Accepted Answer

A)  a flavin nucleotide. 
B)  a pyrophosphate bond. 
C)  an adenine nucleotide. 
D)  nicotinamide. 
E)  two ribose residues. 
A)  a flavin nucleotide. 
B)  a pyrophosphate bond. 
C)  an adenine nucleotide. 
D)  nicotinamide. 
E)  two ribose residues.

Question 10

In glycolysis, the enzyme pyruvate kinase catalyzes this reaction:
phosphoenolpyruvate + ADP $\rightarrow$ pyruvate + ATP
Given the information below, show how you would calculate the equilibrium constant for this reaction. (R = 8.315 J/mol · K; T = 298 K)
Reaction 1: ATP$\rightarrow$ ADP + Pi
$\Delta$ G'° = -30.5 kJ/mol
Reaction 2: phosphoenolpyruvate $\rightarrow$ pyruvate + Pi
$\Delta$ G'° = -61.9 kJ/mol

Accepted Answer

To calculate the equilibrium constant fo

Question 11

For the reaction A $\rightarrow$B, the Keq' is 10-6. If a reaction mixture originally contains 1 mmol of A and 1 mmol of B, which statement must be TRUE?

Accepted Answer

A)  At equilibrium, there will be still be equal levels of A and B. 
B)  The rate of the reaction is very slow. 
C)  At equilibrium, the amount of A will greatly exceed the amount of B. 
D)  The reaction will proceed toward B at a very high rate. 
E)  $\Delta$G'° for the reaction will be large and positive. 
A)  At equilibrium, there will be still be equal levels of A and B. 
B)  The rate of the reaction is very slow. 
C)  At equilibrium, the amount of A will greatly exceed the amount of B. 
D)  The reaction will proceed toward B at a very high rate. 
E)  $\Delta$G'° for the reaction will be large and positive.

Question 12

Under cellular conditions (37°C), what is the actual free energy for the reaction shown below when the ratio of glucose-6-phosphate to fructose-6-phosphate is 0.8:0.2? glucose-6-phosphate $\leftrightarrow$ fructose-6-phosphate $\Delta$G'° = 1.7 kJ/mol

Accepted Answer

A)  1730 kJ/mol 
B)  1870 KJ/mol 
C)  1.73 kJ/mol 
D)  -1.73 kJ/mol 
E)  -1.87 kJ/mol 
A)  1730 kJ/mol 
B)  1870 KJ/mol 
C)  1.73 kJ/mol 
D)  -1.73 kJ/mol 
E)  -1.87 kJ/mol

Question 13

Which statement is TRUE for the reaction A + B $\leftrightarrow$ C + D if its Keq for the reaction is 104?

Accepted Answer

A)  When the reaction has reached equilibrium, there will be significantly more A and B than C and D in solution. 
B)  The formation of A and B will proceed at a high rate. 
C)  The value of $\Delta$G'° will be large and positive. 
D)  All of the statements are true. 
E)  None of the statements is true. 
A)  When the reaction has reached equilibrium, there will be significantly more A and B than C and D in solution. 
B)  The formation of A and B will proceed at a high rate. 
C)  The value of $\Delta$G'° will be large and positive. 
D)  All of the statements are true. 
E)  None of the statements is true.

Question 14

Alcohol dehydrogenase catalyzes the following reversible reaction:
acetaldehyde + NADH + H+ $\rightarrow$ethanol + NAD+
Use the following information to answer the questions below:
acetaldehyde + 2H+ + 2e- $\rightarrow$ ethanol
E'° = -0.20 V
NAD+ + H+ + 2e- $\rightarrow$NADH
E'° = -0.32 V
The Faraday constant,  , is 96.48 kJ/V · mol.
(a) Calculate $\Delta$G'° for the reaction as written. Show your work.
(b) Given your answer to (a), what is the $\Delta$G'° for the reaction occurring in the reverse direction?
(c) Which reaction (forward or reverse) will tend to occur spontaneously under standard conditions?
(d) In the cell, the reaction actually proceeds in the direction that has a positive $\Delta$G'°. Explain how this could be possible.

Accepted Answer

(a) To calculate the standard Gibbs free

Question 15

Given that the $\Delta$ G'0o values for the hydrolysis of glucose 1-phosphate and glucose 6-phosphate are approximately -21 kJ/mol and -14 kJ/mol, respectively, which statement is TRUE regarding the following isomerizations? glucose 1-phosphate $\leftrightarrow$ glucose 6-phosphate

Accepted Answer

A)  Under cellular conditions the direction of the reaction depends on the concentrations of glucose 1-phosphate and glucose 6-phosphate. 
B)  The overall rate of this reaction is relatively slow. 
C)  An increase in entrophy "drives" this reaction. 
D)  The value of $\Delta$ G'o for this isomerization reaction is small and positive. 
E)  All the statements are true for the isomerization reaction shown above. 
A)  Under cellular conditions the direction of the reaction depends on the concentrations of glucose 1-phosphate and glucose 6-phosphate. 
B)  The overall rate of this reaction is relatively slow. 
C)  An increase in entrophy "drives" this reaction. 
D)  The value of $\Delta$ G'o for this isomerization reaction is small and positive. 
E)  All the statements are true for the isomerization reaction shown above.

Question 16

In the following reaction, which molecule is the reducing agent? glyceraldehyde-3-phosphate + Pi + NAD+ $\rightarrow$  1,3-bisphosphoglycerate + NADH + H+

Accepted Answer

A)  1,3-bisphosphoglycerate 
B)  NADH 
C)  H+ 
D)  glyceraldehyde-3-phosphate 
E)  NAD+ 
A)  1,3-bisphosphoglycerate 
B)  NADH 
C)  H+ 
D)  glyceraldehyde-3-phosphate 
E)  NAD+

Question 17

Which statement is NOT true?

Accepted Answer

A)  The carbon adjacent to a carbonyl can be resonance stabilized to form a carbanion. 
B)  A carbonyl carbon can be made more electrophilic by a nearby metal ion. 
C)  The carbon adjacent to an imine can be resonance stabilized to form a carbanion 
D)  Decarboxylation of an $\alpha$-keto acid goes through a carbocation intermediate. 
E)  A Claisen ester condensation reaction goes through a carbanion intermediate. 
A)  The carbon adjacent to a carbonyl can be resonance stabilized to form a carbanion. 
B)  A carbonyl carbon can be made more electrophilic by a nearby metal ion. 
C)  The carbon adjacent to an imine can be resonance stabilized to form a carbanion 
D)  Decarboxylation of an $\alpha$-keto acid goes through a carbocation intermediate. 
E)  A Claisen ester condensation reaction goes through a carbanion intermediate.

Question 18

Which atom is a possible nucleophile?

Accepted Answer

A)  an oxygen atom in a hydroxide ion 
B)  an oxygen atom of a carboxylate group 
C)  a nitrogen atom of a deprotonated amine 
D)  All of the answers are correct. 
E)  None of the answers is correct. 
A)  an oxygen atom in a hydroxide ion 
B)  an oxygen atom of a carboxylate group 
C)  a nitrogen atom of a deprotonated amine 
D)  All of the answers are correct. 
E)  None of the answers is correct.

Question 19

Which biochemical reaction is NOT used in the process of activating a biological molecule?

Accepted Answer

A)  Phosphoryl group transfer from ATP forming a new phosphoester linkage. 
B)  Formation of a thioester bond by linking a molecule to coenzyme A. 
C)  Pyrophosphoryl group transfer from ATP forming a new phosphodiester linkage. 
D)  Adenylyl transfer from ATP by forming a new phosphodiester linkage. 
E)  All these reactions may be involved. 
A)  Phosphoryl group transfer from ATP forming a new phosphoester linkage. 
B)  Formation of a thioester bond by linking a molecule to coenzyme A. 
C)  Pyrophosphoryl group transfer from ATP forming a new phosphodiester linkage. 
D)  Adenylyl transfer from ATP by forming a new phosphodiester linkage. 
E)  All these reactions may be involved.

Question 20

Which statement is TRUE regarding the actual free-energy change for a reaction?

Accepted Answer

A)  The actual free-energy change varies depending on the pathway by which the reaction occurs. 
B)  When the standard free energy is large and positive, the reaction will never occur. 
C)  The actual free energy varies depending on the standard free energy and the concentration of reactants and products. 
D)  All of the statements are true. 
E)  None of the statements is true. 
A)  The actual free-energy change varies depending on the pathway by which the reaction occurs. 
B)  When the standard free energy is large and positive, the reaction will never occur. 
C)  The actual free energy varies depending on the standard free energy and the concentration of reactants and products. 
D)  All of the statements are true. 
E)  None of the statements is true.

Exam 13: Bioenergetics and Biochemical Reaction Types

Which statement is FALSE regarding carbonyl groups?

Which factor does NOT contribute to the large, negative, free-energy change upon hydrolysis of "high-energy" compounds?

The reaction A + B →\rightarrow→ C has a Δ\DeltaΔ G'° of -20 kJ/mol at 25° C. Starting under standard conditions, one can predict that:

The reaction ATP →\rightarrow→ ADP + Pi is an example of a(n) _____ reaction.

The hydrolysis of ATP has a large negative Δ\DeltaΔ G'°; nevertheless it is stable in solution due to:

Consider the reaction: A + B →\rightarrow→ C + D. If the equilibrium constant for this reaction is a large number (say, 10,000), what do we know about the standard free-energy change ( Δ\DeltaΔ G'°) for the reaction? Describe the relationship between Keq' and Δ\DeltaΔ G'°.

Hydrolysis of 1 M glucose 6-phosphate catalyzed by glucose 6-phosphatase is 99% complete at equilibrium (i.e., only 1% of the substrate remains). Which statement is MOST nearly correct? (R = 8.315 J/mol · K; T = 298 K)

The structure of NAD+ does NOT include:

For the reaction A →\rightarrow→ B, the Keq' is 10-6. If a reaction mixture originally contains 1 mmol of A and 1 mmol of B, which statement must be TRUE?

Under cellular conditions (37°C), what is the actual free energy for the reaction shown below when the ratio of glucose-6-phosphate to fructose-6-phosphate is 0.8:0.2? glucose-6-phosphate ↔\leftrightarrow↔ fructose-6-phosphate Δ\DeltaΔ G'° = 1.7 kJ/mol

Which statement is TRUE for the reaction A + B ↔\leftrightarrow↔ C + D if its Keq for the reaction is 104?

Given that the Δ\DeltaΔ G'0o values for the hydrolysis of glucose 1-phosphate and glucose 6-phosphate are approximately -21 kJ/mol and -14 kJ/mol, respectively, which statement is TRUE regarding the following isomerizations? glucose 1-phosphate ↔\leftrightarrow↔ glucose 6-phosphate

In the following reaction, which molecule is the reducing agent? glyceraldehyde-3-phosphate + Pi + NAD+ →\rightarrow→ 1,3-bisphosphoglycerate + NADH + H+

Which statement is NOT true?

Which atom is a possible nucleophile?

Which biochemical reaction is NOT used in the process of activating a biological molecule?

Which statement is TRUE regarding the actual free-energy change for a reaction?

The Foundations of Biochemistry

Water

Amino Acids, Peptides, and Proteins

The Three-Dimensional Structure of Proteins

Protein Function

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

DNA-Based Information Technologies

Lipids

Biological Membranes and Transport

Biosignaling

Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Oxidative Phosphorylation and Photophosphorylation

Carbohydrate Biosynthesis in Plants and Bacteria

Lipid Biosynthesis

Biosynthesis of Amino Acids, Nucleotides, and Related Molecules

Hormonal Regulation and Integration of Mammalian Metabolism

Genes and Chromosomes

DNA Metabolism

RNA Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

The reaction A + B $\rightarrow$ C has a $\Delta$ G'° of -20 kJ/mol at 25° C. Starting under standard conditions, one can predict that:

The reaction ATP $\rightarrow$ ADP + P_i is an example of a(n) _____ reaction.

The hydrolysis of ATP has a large negative $\Delta$ G'°; nevertheless it is stable in solution due to:

Consider the reaction: A + B $\rightarrow$ C + D. If the equilibrium constant for this reaction is a large number (say, 10,000), what do we know about the standard free-energy change ( $\Delta$ G'°) for the reaction? Describe the relationship between K_eq' and $\Delta$ G'°.

The structure of NAD⁺ does NOT include:

For the reaction A $\rightarrow$ B, the K_eq' is 10^-⁶. If a reaction mixture originally contains 1 mmol of A and 1 mmol of B, which statement must be TRUE?

Under cellular conditions (37°C), what is the actual free energy for the reaction shown below when the ratio of glucose-6-phosphate to fructose-6-phosphate is 0.8:0.2? glucose-6-phosphate $\leftrightarrow$ fructose-6-phosphate $\Delta$ G'° = 1.7 kJ/mol

Which statement is TRUE for the reaction A + B $\leftrightarrow$ C + D if its K_eq for the reaction is 10⁴?

Given that the $\Delta$ G'0^o values for the hydrolysis of glucose 1-phosphate and glucose 6-phosphate are approximately -21 kJ/mol and -14 kJ/mol, respectively, which statement is TRUE regarding the following isomerizations? glucose 1-phosphate $\leftrightarrow$ glucose 6-phosphate

In the following reaction, which molecule is the reducing agent? glyceraldehyde-3-phosphate + P_i + NAD⁺ $\rightarrow$ 1,3-bisphosphoglycerate + NADH + H⁺