1. If the delta G'? of the reaction A --> B is -40 kJ/mol,
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 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 thatG'� is -60 kJ/mol.
The reaction A + B --->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.
Which of the following compounds has the largest negative value for the standard free-energy change (G'�) upon hydrolysis?
A) Acetic anhydride
B) Glucose 6-phosphate
C) Glutamine
D) Glycerol 3-phosphate
E) Lactose
For the following reaction, delta G'� = +29.7 kJ/mol.
L-Malate + NAD+ --->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.
For the reaction A --->B, the Keq' is 104. If a reaction mixture originally contains 1 mmol of A and no B, which one of the following 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.
For the reaction A --->B, the Keq' is 10-6. If a reaction mixture originally contains 1 mmol of A and 1 mmol of B, which one of the following 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.
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 theG'� 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 the above conditions is sufficient.
Which of the following is not nucleophilic?
A) A proton
B) A carbanion
C) An imidazole
D) A hydroxide
E) A carboxylic acid
Which of the following is not electrophilic?
A) A proton
B) A sulfhydryl
C) A protonated imine
D) A carbonyl group
E) A phosphoryl group
Which of the following 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 -keto acid goes through a carbocation intermediate.
E) A Claisen ester condensation reaction goes through a carbanion intermediate.
The reaction ATP ---> ADP + Pi is an example of a_______reaction.
A) homolytic cleavage
B) internal rearrangement
C) free radical
D) group transfer
E) oxidation/reduction
Which of the following 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.
All of the following contribute to the large, negative, free-energy change upon hydrolysis of "high-energy" compounds except:
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.
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.
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.
Which one of the following compounds does 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)
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.
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.
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.
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 above.
The standard reduction potentials (E'�) for the following half reactions are given.
Fumarate + 2H+ + 2e- --->succinate E'� = +0.031 V
FAD + 2H+ + 2e- --->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, which of the following 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.
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+ --->oxaloacetate + NADH + H+.
B) malate + NADH + H+ --->oxaloacetate + NAD+.
C) NAD+ + NADH + H+ --->malate + oxaloacetate.
D) NAD+ + oxaloacetate --->NADH + H+ + malate.
E) oxaloacetate + NADH + H+ --->malate + NAD+.
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.
Which of the following 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.-->
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.
For the reaction A --->B, delta G'� = -60 kJ/mol. The reaction is started with 10 mmol of A; no B is initially present. After 24 hours,
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