Deck 13: Bioenergetics and Biochemical Reaction Types

Question 1

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change ( $\Delta$ G'°) of 23.8 kJ/mol. Under what conditions encountered in a normal cell will the free-energy change ( $\Delta$ G) be negative, enabling the reaction to proceed spontaneously to the right?

A) Under standard conditions, enough energy is released to drive the reaction to the right.
B) The reaction will not go to the right spontaneously under any conditions because the $\Delta$ G'° is positive.
C) The reaction will proceed spontaneously to the right if there is a high concentration of products relative to the concentration of fructose 1,6-bisphosphate.
D) The reaction will proceed spontaneously to the right if there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products.
E) None of these conditions is sufficient.

Answer 1

Under standard conditions, enough energy is released to drive the reaction to the right.

Question 2

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?

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.

Answer 2

At equilibrium, there will be still be equal levels of A and B.

Question 3

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)

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.

Answer 3

$\Delta$ G'° is -11 kJ/mol.

Question 4

Which compound has the LARGEST negative value for the standard free-energy change ( $\Delta$ G'°) upon hydrolysis?

A) acetic anhydride
B) glucose 6-phosphate
C) glutamine
D) glycerol 3-phosphate
E) lactose

Question 5

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

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 K_eq'.

Question 6

Which statement is TRUE about oxidation-reduction reactions?

A) They usually proceed through homolytic cleavage.
B) During oxidation a compound gains electrons.
C) Dehydrogenases typically remove two electrons and two hydrides.
D) There are four commonly accessed oxidation states of carbon.
E) Every oxidation must be accompanied by a reduction.

Question 7

Which statement is NOT true?

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 8

For the reaction A $\rightarrow$ B, $\Delta$ G'° = -60 kJ/mol. The reaction is started with 10 mmol of A; no B is initially present. After 24 hours, analysis reveals the presence of 2 mmol of B, 8 mmol of A. Which statement is the MOST likely explanation?

A) A and B have reached equilibrium concentrations.
B) An enzyme has shifted the equilibrium toward A.
C) B formation is kinetically slow; equilibrium has not been reached by 24 hours.
D) Formation of B is thermodynamically unfavorable.
E) The result described is impossible, given the fact that $\Delta$ G'° is -60 kJ/mol.

Question 9

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

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 10

When a mixture of 3-phosphoglycerate and 2-phosphoglycerate is incubated at 25 °C with phosphoglycerate mutase until equilibrium is reached, the final mixture contains six times as much 2-phosphoglycerate as 3-phosphoglycerate. Which statement is MOST nearly correct, when applied to the reaction as written? (R = 8.315 J/mol · K; T = 298 K) 3-phosphoglycerate $\rightarrow$ 2-phosphoglycerate

A) $\Delta$ G'° is -4.44 kJ/mol.
B) $\Delta$ G'° is zero.
C) $\Delta$ G'°is +12.7 kJ/mol.
D) $\Delta$ G'°is incalculably large and positive.
E) $\Delta$ G'° cannot be calculated from the information given.

Question 11

Which item is NOT nucleophilic?

A) a proton
B) a carbanion
C) an imidazole
D) a hydroxide
E) a carboxylic acid

Question 12

Which item is NOT electrophilic?

A) a proton
B) a sulfhydryl
C) a protonated imine
D) a carbonyl group
E) a phosphoryl group

Question 13

If the $\Delta$ G'° of the reaction A $\rightarrow$ B is -40 kJ/mol, under standard conditions the reaction:

A) is at equilibrium.
B) will never reach equilibrium.
C) will not occur spontaneously.
D) will proceed at a rapid rate.
E) will proceed spontaneously from A to B.

Question 14

During glycolysis, glucose 1-phosphate is converted to fructose 6-phosphate in two successive reactions: glucose 1-phosphate $\rightarrow$ glucose 6-phosphate
$\Delta$ G'° = -7.1 kJ/mol
Glucose 6-phosphate $\rightarrow$ fructose 6-phosphate
$\Delta$ G'° = +1.7 kJ/mol
$\Delta$ G'° for the overall reaction is:

A) -8.8 kJ/mol.
B) -7.1 kJ/mol.
C) -5.4 kJ/mol.
D) +5.4 kJ/mol.
E) +8.8 kJ/mol.

Question 15

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

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

Question 16

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:

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 17

For the reaction A $\rightarrow$ B, the K_eq' is 10⁴. If a reaction mixture originally contains 1 mmol of A and no B, which statement must be TRUE?

A) At equilibrium, there will be far more B than A.
B) The rate of the reaction is very slow.
C) The reaction requires coupling to an exergonic reaction in order to proceed.
D) The reaction will proceed toward B at a very high rate.
E) $\Delta$ G'° for the reaction will be large and positive.

Question 18

For the following reaction, $\Delta$ G'° = +29.7 kJ/mol. L-Malate + NAD⁺ $\rightarrow$ oxaloacetate + NADH + H⁺
The reaction as written:

A) can never occur in a cell.
B) can occur in a cell only if it is coupled to another reaction for which $\Delta$ G'° is positive.
C) can occur only in a cell in which NADH is converted to NAD⁺ by electron transport.
D) cannot occur because of its large activation energy.
E) may occur in cells at some concentrations of substrate and product.

Question 19

The $\Delta$ G'° values for the two reactions shown below are given. oxaloacetate + acetyl-CoA + H₂O $\rightarrow$ citrate + CoASH
$\Delta$ G'° = -32.2 kJ/mol
Citrate
Synthase
Oxaloacetate + acetate $\rightarrow$ citrate
$\Delta$ G'° = -1.9 kJ/mol
Citrate lyase
What is the $\Delta$ G'° for the hydrolysis of acetyl-CoA?
Acetyl-CoA + H₂O $\rightarrow$ acetate + CoASH + H⁺

A) -34.1 kJ/mol
B) -32.2 kJ/mol
C) -30.3 kJ/mol
D) +61.9 kJ/mol
E) +34.1 kJ/mol

Question 20

When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme phosphohexose isomerase (which catalyzes the interconversion of these two compounds) until equilibrium is reached, the final mixture contains twice as much glucose 6-phosphate as fructose 6-phosphate. Which one of the following statements is best applied to this reaction outlined below? (R = 8.315 J/mol · K; T = 298 K) glucose 6-phosphate $\rightarrow$ fructose 6-phosphate

A) $\Delta$ G'° is incalculably large and negative.
B) $\Delta$ G'° is -1.72 kJ/mol.
C) $\Delta$ G'° is zero.
D) $\Delta$ G'° is +1.72 kJ/mol.
E) $\Delta$ G'° is incalculably large and positive.

Question 21

The hydrolysis of phosphoenolpyruvate proceeds with a $\Delta$ G'° of about -62 kJ/mol. The greatest contributing factors to this reaction are the destabilization of the reactants by electostatic repulsion and stabilization of the product pyruvate by:

A) electrostatic attraction.
B) ionization.
C) polarization.
D) resonance.
E) tautomerization.

Question 22

Which compound is classified as high energy?

A) phosphoarginine
B) succinyl-CoA
C) fatty acid-CoA
D) All of the answers are correct.
E) None of the answers is correct.

Question 23

Biological oxidation-reduction reactions always involve:

A) direct participation of oxygen.
B) formation of water.
C) mitochondria.
D) transfer of electron(s).
E) transfer of hydrogens.

Question 24

Which amino acid can participate in nucleophilic catalysis?

A) His
B) Cys
C) Tyr
D) All of the answers are correct.
E) None of the answers is correct.

Question 25

Which compound(s) do(es) NOT have a large negative free energy of hydrolysis?

A) 1,3-bis phosphoglycerate
B) 3-phosphoglycerate
C) ADP
D) phosphoenolpyruvate
E) thioesters (e.g., acetyl-CoA)

Question 26

Biological oxidation-reduction reactions never involve:

A) transfer of e^- from one molecule to another.
B) formation of free e^-.
C) transfer of H⁺ (or H₃O⁺) from one molecule to another.
D) formation of free H⁺ (or H₃O⁺).
E) None of the answers is correct.

Question 27

Which is the MOST oxidized carbon atom in a ketohexose sugar?

A) C1
B) C2
C) C3
D) C5
E) C6

Question 28

Which atom is a common electrophile?

A) a hydrogen atom
B) an oxygen atom of a carbonyl group
C) an oxygen atom of a phosphate group
D) All of the answers are correct.
E) None of the answers is correct.

Question 29

The standard reduction potentials (E'°) for the following half reactions are given. fumarate + 2H⁺ + 2e^- $\rightarrow$ succinate
E'° = +0.031 V
FAD + 2H⁺ + 2e^- $\rightarrow$ FADH₂
E'° = -0.219 V
If you mixed succinate, fumarate, FAD, and FADH₂ together, all at l M concentrations and in the presence of succinate dehydrogenase, what would happen initially?

A) Fumarate and succinate would become oxidized; FAD and FADH₂ would become reduced.
B) Fumarate would become reduced; FADH₂ would become oxidized.
C) No reaction would occur because all reactants and products are already at their standard concentrations.
D) Succinate would become oxidized; FAD would become reduced.
E) Succinate would become oxidized; FADH₂ would be unchanged because it is a cofactor.

Question 30

Which statement is NOT true for the nicotinamide cofactors?

A) The oxidized form is positively charged.
B) The reduced form has a large extinction coefficient at 340 nm.
C) The oxidized form provides reducing equivalents to other molecules.
D) Oxidation-reduction reactions with nicotinamides usually involve hydride transfer.
E) Enzymes transfer hydrides stereospecifically to one or the other side of the nicotinamide ring.

Question 31

Muscle contraction involves the conversion of:

A) chemical energy to kinetic energy.
B) chemical energy to potential energy.
C) kinetic energy to chemical energy.
D) potential energy to chemical energy.
E) potential energy to kinetic energy.

Question 32

The immediate precursors of DNA and RNA synthesis in the cell all contain:

A) 3' triphosphates.
B) 5' triphosphates.
C) adenine.
D) deoxyribose.
E) ribose.

Question 33

Which carbon atom is in the MOST oxidized state?

A) a carbon in an alkyl group
B) a carbon in a ketone group
C) a carbon in carbon dioxide
D) a carbon in a carboxylic acid group
E) a carbon in an alcohol group

Question 34

Which carbon atom is in the MOST reduced state?

A) a carbon in an alkyl group
B) a carbon in an aldehyde group
C) a carbon in a ketone group
D) a carbon in a carboxylic acid group
E) a carbon in an alcohol group

Question 35

Which atom is a possible nucleophile?

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 36

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

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 37

Which statement is always TRUE for $\Delta$ G'?

A) The temperature is 25°C.
B) The pH is 7.0.
C) The value for $\Delta$ G' is a constant.
D) The initial concentration of each component is 1.0 M.
E) The pressure is 1 atm.

Question 38

$\Delta$ G'° for the hydrolysis of ATP is -30.5 kJ/mol. What effect will doubling ATP concentration have on the value of $\Delta$ G'° for ATP hydrolysis?

A) Make the value of $\Delta$ G'° more negative.
B) Make the value of $\Delta$ G'° less negative.
C) There will be no change in the value of $\Delta$ G'°.
D) Make the value of $\Delta$ G'° more positive.
E) Make the value of $\Delta$ G'° less positive.

Question 39

E'° of the NAD⁺/NADH half reaction is -0.32 V. The E'° of the oxaloacetate/malate half reaction is -0.175 V. When the concentrations of NAD⁺, NADH, oxaloacetate, and malate are all 10^-5 M, the "spontaneous" reaction is:

A) malate + NAD⁺ $\rightarrow$ oxaloacetate + NADH + H⁺.
B) malate + NADH + H⁺ $\rightarrow$ oxaloacetate + NAD⁺.
C) NAD⁺ + NADH + H⁺ $\rightarrow$ malate + oxaloacetate.
D) NAD⁺ + oxaloacetate $\rightarrow$ NADH + H⁺ + malate.
E) oxaloacetate + NADH + H⁺ $\rightarrow$ malate + NAD⁺.

Question 40

The structure of NAD⁺ does NOT include:

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

Question 41

Which statement is TRUE?

A) The rate of a reaction that generates NAD⁺ can be determined by measuring the rate of increase in absorbance at 340 nm.
B) NADH and NADPH are classified as pyrimidine nucleotides due to the presence of the nicotinamide ring which resembles pyrimidine.
C) NAD⁺ has a net charge of +1.
D) In many cells, the ratio of NADP⁺ to NADPH is high favouring the reduction of biomolecules.
E) A phosphoanhydride bonds links the two nucleotides in nicotinamide dinucleotides.

Question 42

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

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

Question 43

Under standard conditions, is the oxidation of free FADH₂ by ubiquinone sufficiently exergonic to drive the synthesis of ATP?

A) no ,as oxidation of FADH₂ by ubiquinone generates 33.6 kJ/mol
B) no, as oxidation of FADH₂ by ubiquinone generates 50.9 kJ/mol
C) no, as oxidation of FADH₂ by ubiquinone generates -25.5 kJ/mol
D) yes, as oxidation of FADH₂ by ubiquinone generates -33.6 kJ/mol
E) yes, as oxidation of FADH₂ by ubiquinone generates -50.9 kJ/mol

Question 44

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

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 45

Which statement is NOT true regarding the biochemical standard state?

A) The [H⁺] is 10^-7M.
B) Temperature is 28°C.
C) All reactants and products are present at 1 M concentrations.
D) The pressure is 1 atm.
E) The concentration of water is essentially constant at 55.5 M.

Question 46

What is the equilibrium constant for the reaction shown below? glutathione + NADPH + H⁺ $\leftrightarrow$ reduced glutathione + reduced glutathione + NADP⁺

A) 0.073
B) 1.073
C) 7.03
D) 17.4
E) 1,487

Question 47

What is the CORRECT order of substances in terms of electronegativity, greatest to least?

A) H $\rightarrow$ C $\rightarrow$ N $\rightarrow$ S $\rightarrow$ O
B) H $\rightarrow$ C $\rightarrow$ S $\rightarrow$ O $\rightarrow$ N
C) O $\rightarrow$ S $\rightarrow$ N $\rightarrow$ C $\rightarrow$ H
D) N $\rightarrow$ O $\rightarrow$ S $\rightarrow$ H $\rightarrow$ C
E) O $\rightarrow$ N $\rightarrow$ S $\rightarrow$ C $\rightarrow$ O

Question 48

Under standard conditions, is the oxidation of NADH by free FAD sufficiently exergonic to drive the synthesis of ATP?

A) no, as oxidation of NADH by FAD only generates -9.65 kJ/mol
B) no, as oxidation of NADH by FAD only generates -19.3 kJ/mol
C) no, as oxidation of NADH by FAD only generates 9.65 kJ/mol
D) no, as oxidation of NADH by FAD only generates 19.3 kJ/mol
E) yes, as oxidation of NADH by FAD generates -104.2 kJ/mol

Question 49

The phosphate bonds found in a phosphorylated tyrosine and in an acyl phosphate are likely to have similar standard free energies of hydrolysis.

A) true
B) false because hydrolysis of a phosphorylated tyrosine would release significantly more energy than hydrolysis of an acyl phosphate.
C) false because hydrolysis of an acyl phosphate would release significantly more energy than hydrolysis of a phosphorylated tyrosine

Question 50

Which statement about NAD⁺ and NADH is FALSE?

A) NAD⁺ is oxidized to NADH by $\alpha$ -ketoglutarate dehydrogenase.
B) Lactate dehydrogenase binds NAD⁺ tightly in the Rossmann fold.
C) NAD⁺ accepts both electrons as a hydride ion.
D) NAD⁺ is oxidized to NADH by $\alpha$ -ketoglutarate dehydrogenase, and lactate dehydrogenase binds NAD⁺ tightly in the Rossmann fold.
E) NAD⁺ is oxidized to NADH by $\alpha$ -ketoglutarate dehydrogenase, and NAD⁺ accepts both electrons as a hydride ion.

Question 51

Which statement is FALSE regarding carbonyl groups?

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 52

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

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

Question 53

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

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

Question 54

Which atom is the MOST electronegative?

A) C
B) N
C) P
D) O
E) S

Question 55

What is the equilibrium constant for a reaction with a standard free-energy change of +25kJ/mol?

A) -1.1
B) -10.1
C) 4.1 × 10^-5
D) 10.1
E) 2.4 × 10⁴

Question 56

Which statement is FALSE regarding biological oxidations?

A) The redox potential is the affinity of a substance to accept electrons.
B) Oxidation can occur by addition of oxygen to a molecule.
C) Electrons are transferred from substances with a high reduction potential to substances with a lower reduction potential.
D) Oxidases, oxygenases, and dehydrogenases are all enzymes that catalyze biological oxidation reactions.
E) NAD⁺ is a cosubstrate of certain dehydrogenases and always accepts electrons in the form of hydride ions.

Question 57

Which atom is the LEAST electronegative?

A) C
B) N
C) H
D) O
E) S

Question 58

What is the $\Delta$ G'° for the following reaction if the concentrations of glucose-6-phosphate and glucose-1-phosphate at equilibrium are 19 mM and 1 mM, respectively? glucose-6-phosphate $\leftrightarrow$ glucose-1-phosphate

A) 7.3 kJ/mol
B) 7.6 kJ/mol
C) -7.3 kJ/mol
D) -7.6 kJ/mol
E) $\Delta$ G'° cannot be determined from the information given.

Question 59

If the equilibrium constant for the dissociation of lactic acid is 1.38 × 10^-4, what is the $\Delta$ G°' for this reaction?

A) 16.3kJ/mol
B) -16.3 kJ/mol
C) 16.96 kJ/mol
D) -16.96 kJ/mol
E) 27.5 kJ/mol

Question 60

Which molecule is NOT considered a universal electron carrier?

A) NADH
B) ATPF
C) ADH₂
D) FMNH₂
E) both ATPF and FMNH₂

Question 61

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

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 62

Acyl phosphates, phosphoesters, and phosphaoanhydrides are compounds of significantly different phosphoryl group-transfer potentials. Which choice CORRECTLY ranks these phosphorylated intermediates with respect to their phosphoryl group-transfer potential from highest to lowest?

A) 1,3-bisphosphoglycerate $\rightarrow$ adenosine triphosphate $\rightarrow$ glucose 1-phosphate
B) glucose 1-phosphate $\rightarrow$ adenosine triphosphate $\rightarrow$ 1,3-bisphosphoglycerate
C) adenosine triphosphate $\rightarrow$ 1,3-bisphosphoglycerate $\rightarrow$ glucose 1-phosphate
D) adenosine triphosphate $\rightarrow$ glucose 1-phosphate $\rightarrow$ 1,3-bisphosphoglycerate
E) 1,3-bisphosphoglycerate $\rightarrow$ glucose 1-phosphate $\rightarrow$ adenosine triphosphate

Question 63

Which statement is TRUE regarding coupled reactions?

A) The standard free energy changes of the coupled reactions are additive, and their equilibrium constants are multiplicative.
B) The coupled reactions must share a common intermediate.
C) The free energy of the endergonic reaction must be greater in magnitude than the free energy of the exergonic reaction.
D) The standard free energy changes of the coupled reactions are additive, their equilibrium constants are multiplicative, and the coupled reactions must share a common intermediate.
E) None of the statements is true.

Question 64

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

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.

Question 65

Which statement is TRUE with respect to the change in free energy for a given reaction?

A) $\Delta$ G is linearly proportional to the rate of the reaction.
B) $\Delta$ G is a logarithmic function of the equilibrium constant.
C) $\Delta$ G provides no information about the rate of the reaction.
D) All of the statements are true.
E) None of the statements is true.

Question 66

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

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

Question 67

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

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 68

Which statement about Gibbs free energy is FALSE?

A) At equilibrium, the actual free energy is zero and $\Delta$ G'° = -RTln K_eq
B) When the reactants are in excess of their equilibrium concentrations, the conversion of product to reactant is more likely to occur.
C) The standard free energy of a redox reaction can be determined if the standard reduction potentials of both the products and reactants are known.
D) All of the statements are false.
E) None of the statements is false.

Question 69

Which statement is TRUE regarding $\Delta$ G'?

A) $\Delta$ G' is negative when the reaction is occurring spontaneously.
B) $\Delta$ G' is zero when the rate of the forward and reverse reactions are equal.
C) $\Delta$ G' becomes less negative as the reaction proceeds spontaneously.
D) All of the statements are true.
E) None of the statements is true.

Question 70

Which enzyme catalyzes phosphate transfer reactions between nucleotides?

A) nucleoside diphosphate kinase
B) creatine kinase
C) adenylate kinase
D) both nucleoside diphosphate kinase and adenylate kinase
E) both creatine kinase and adenylate kinase

Question 71

Which statement is TRUE for the equilibrium constant?

A) The equilibrium constant is independent of the initial concentrations of reactants and products.
B) When the equilibrium constant is greater than one, the standard free energy change for the reaction favors production of reactants.
C) The equilibrium constant does not vary with changes in pH.
D) The equilibrium constant does not vary with changes in temperature.
E) A relatively small change in the equilibrium constant is associated with a large change in the standard free-energy change.

Question 72

Which phosphorylated amino acid is used by invertebrates in a similar manner that vertebrates use phosphocreatine?

A) phosphocysteine
B) phosphoarginine
C) phosphohistidine
D) phosphoaspartate
E) phosphotyrosine

Question 73

Which statement regarding redox reactions is TRUE?

A) NADH and FADH₂ are major electron acceptors in the oxidation of fuel molecules.
B) In glycolysis, the conversion of 2-phosphpoglycerate to phosphoenolpyruvate is a redox reaction.
C) In a redox reaction, the oxidation state of the substrate remains unchanged.
D) A redox reaction is spontaneous when the substrate has a greater reduction potential than the product.
E) The Nerst equation relates the standard reduction potential of a redox pair to its actual reduction potential at any concentration of either the oxidized or reduced form of the species.

Question 74

The value of $\Delta$ G'^o for the hydrolysis of a phosphoanhydride in ATP bonds becomes a larger negative number with increasing pH above 7.0. Explain why this occurs.

Question 75

Explain the relationships among the change in the degree of order, the change in entropy, and the change in free energy that occur during a chemical reaction.

Question 76

Under standard conditions, ATP can be used in phosphate-transfer reactions to generate which molecule?

A) phosphocreatine
B) glycerol-3-phosphate
C) phosphoenolpyruvate
D) 1,3-bisphosphoglycerate
E) All of the answers are correct.

Question 77

Which conjugate redox pair is involved in biological oxidations?

A) Fe²⁺ and Fe³⁺
B) NADP⁺ and NAD⁺
C) FMN and FADH2
D) succinate and fumarate
E) both Fe²⁺ and Fe³⁺ and succinate and fumarate

Question 78

Which redox reaction(s) will NOT proceed as written if the initial concentrations of reactants and products are equal? I. pyruvate + NADH $\rightarrow$ lactate + NAD⁺
II. FADH₂ + NAD⁺ $\rightarrow$ FAD + NADH + H⁺
III. succinate + NAD⁺ $\rightarrow$ fumarate + NADH + H⁺
IV. NADH + H⁺ + ubiquinone $\rightarrow$ NAD⁺ + ubiquinol
V. cytochrome c-Fe³⁺ + cytochrome b-Fe²⁺ $\rightarrow$ cytochrome c-Fe²⁺ + cytochrome b-Fe³⁺

A) I and IV
B) I, IV, and V
C) II
D) II and III
E) IV and V

Question 79

ATP can be generated from a variety pf phosphorylated compounds via phosphate-transfer reactions. Which molecules CANNOT serve as "high-energy" phosphate donors in the synthesis of ATP?

A) phosphate esters
B) acyl phosphates
C) phosphagens
D) phosphoamides
E) enolphosphates

Question 80

_____ is used to illustrate the actual free-energy change of a reaction measured at pH 7 and 37°C.

A) $\Delta$ G
B) $\Delta$ G'
C) $\Delta$ G'°
D) $\Delta$ G°'
E) $\Delta$ G°