Question 1

The flow of material through a reaction pathway usually depends on .

Accepted Answer

A)  control at several steps in the pathway 
B)  control of the first step of the pathway 
C)  covalent modification of the enzyme that catalyzes the reaction 
D)  feed-forward activation 
A)  control at several steps in the pathway 
B)  control of the first step of the pathway 
C)  covalent modification of the enzyme that catalyzes the reaction 
D)  feed-forward activation A

Question 2

The most biochemically complex organisms are .

Accepted Answer

A)  chemoheterotrophs 
B)  photoheterotrophs 
C)  heterotrophs 
D)  autotrophs 
A)  chemoheterotrophs 
B)  photoheterotrophs 
C)  heterotrophs 
D)  autotrophs D

Question 3

What defines a near-equilibrium reaction?

Accepted Answer

A)  Q is close to Keq 
B)  DE0ʹ = 0 
C)  the reaction is a closed system with no flux in or out of the system 
D)  pH is approximately equal to pKeq 
A)  Q is close to Keq 
B)  DE0ʹ = 0 
C)  the reaction is a closed system with no flux in or out of the system 
D)  pH is approximately equal to pKeq A

Question 4

ATP is classified as an energy-rich compound because

Accepted Answer

A)  it complexes with Mg2+. 
B)  it has a relatively low free energy of hydrolysis. 
C)  its complete oxidation to carbon dioxide releases a large amount of energy. 
D)  of the free energy released from cleavage of the phosphoanhydride bond. 
A)  it complexes with Mg2+. 
B)  it has a relatively low free energy of hydrolysis. 
C)  its complete oxidation to carbon dioxide releases a large amount of energy. 
D)  of the free energy released from cleavage of the phosphoanhydride bond.

Question 5

The standard potential for electron transfer can be related to the standard free-energy change for redox reactions by using

Accepted Answer

A)  a calorimeter. 
B)  an electrochemical cell. 
C)  two solutions separated by a salt bridge. 
D)  the Nernst equation. 
E)  the Faraday equation. 
A)  a calorimeter. 
B)  an electrochemical cell. 
C)  two solutions separated by a salt bridge. 
D)  the Nernst equation. 
E)  the Faraday equation.

Question 6

The presence of Mg2+ ions decreases the free energy released by the hydrolysis of ATP.

Accepted Answer

A) True 
 B)False

Question 7

An organism that uses organic molecules as carbon sources and obtains energy by oxidizing inorganic molecules is aan) .

Accepted Answer

A)  photoautotroph 
B)  chemoautotroph 
C)  photoheterotroph 
D)  chemoheterotroph 
A)  photoautotroph 
B)  chemoautotroph 
C)  photoheterotroph 
D)  chemoheterotroph

Question 8

Which is usually the slowest way to regulate a reaction in a metabolic pathway?

Accepted Answer

A)  allosteric modulation 
B)  covalent modification 
C)  changing the enzyme concentration 
D)  All of the above are usually equally as fast 
A)  allosteric modulation 
B)  covalent modification 
C)  changing the enzyme concentration 
D)  All of the above are usually equally as fast

Question 9

Many dehydrogenases can be assayed by measuring the decrease of absorption of NAD+ or the increase of absorption of NADH.

Accepted Answer

A) True 
 B)False

Question 10

Anabolic and catabolic reactions in eukaryotes can occur simultaneously in cells. This is possible because .

Accepted Answer

A)  they all occur in the cytosol 
B)  the anabolic and catabolic pathways do not share any intermediate metabolites 
C)  of the compartmentation of metabolites for the reactions of opposing pathways 
D)  all catabolic reactions are exergonic and all anabolic reactions are endergonic 
A)  they all occur in the cytosol 
B)  the anabolic and catabolic pathways do not share any intermediate metabolites 
C)  of the compartmentation of metabolites for the reactions of opposing pathways 
D)  all catabolic reactions are exergonic and all anabolic reactions are endergonic

Question 11

The ultimate product of complete oxidation of carbohydrates is .

Accepted Answer

A)  carbon dioxide 
B)  acetyl CoA 
C)  pyruvate 
D)  acetate ion 
A)  carbon dioxide 
B)  acetyl CoA 
C)  pyruvate 
D)  acetate ion

Question 12

When a reduction half-reaction is negative, positive), electrons flow to the more readily reduced substance which is negative, positive) in value.

Accepted Answer

A)  negative; negative 
B)  negative; positive 
C)  positive; positive 
D)  positive; negative 
A)  negative; negative 
B)  negative; positive 
C)  positive; positive 
D)  positive; negative

Question 13

Which statement does not explain why many biochemical processes are carried out via multi-step pathways rather than by single-step reactions or only a few steps)?

Accepted Answer

A)  Multi-step pathways allow for more control points to regulate biochemical processes. 
B)  The end products of most pathways can usually be produced only by the pathway reactions that nature has evolved. 
C)  Sharing of intermediates between pathways is facilitated this way. 
D)  There is greater control over the amounts of energy that are consumed or released at any one time. 
A)  Multi-step pathways allow for more control points to regulate biochemical processes. 
B)  The end products of most pathways can usually be produced only by the pathway reactions that nature has evolved. 
C)  Sharing of intermediates between pathways is facilitated this way. 
D)  There is greater control over the amounts of energy that are consumed or released at any one time.

Question 14

The conversion of glucose-1-phosphate to glucose-6-phosphate by the enzyme phosphoglucomutase has a △G°ʹ of -7.6 kJ/mol. Calculate the equilibrium constant for this reaction at 298 K and a pH of 7. R = 8.315 J/K-mol)

Accepted Answer

A)  0.003 
B)  0.047 
C)  1.00 
D)  21 
A)  0.003 
B)  0.047 
C)  1.00 
D)  21

Question 15

A chemical reaction with a negative enthalpy change and a negative entropy change .

Accepted Answer

A)  must be spontaneous 
B)  must be nonspontaneous 
C)  could be either spontaneous or nonspontaneous depending on the temperature 
D)  is not possible 
A)  must be spontaneous 
B)  must be nonspontaneous 
C)  could be either spontaneous or nonspontaneous depending on the temperature 
D)  is not possible

Question 16

The formation of acetyl CoA is driven to completion by

Accepted Answer

A)  the negative standard free energy for the first step of the reaction. 
B)  the negative standard free energy for the final step of the reaction. 
C)  removal of the product pyrophosphate by the enzyme pyrophosphatase. 
D)  the negative free energy for the formation of an ADP intermediate. 
E)  All of the above 
A)  the negative standard free energy for the first step of the reaction. 
B)  the negative standard free energy for the final step of the reaction. 
C)  removal of the product pyrophosphate by the enzyme pyrophosphatase. 
D)  the negative free energy for the formation of an ADP intermediate. 
E)  All of the above

Question 17

A distinct set of metabolic reactions is called a reaction .

Accepted Answer

A)  network 
B)  cycle 
C)  pathway 
D)  mechanism 
A)  network 
B)  cycle 
C)  pathway 
D)  mechanism

Question 18

Both NADH and NADPH are oxidized in cells, but NADH is more often used in specialized pathways to provide hydride ions for reductive reactions in metabolism.

Accepted Answer

A) True 
 B)False

Question 19

Reactions of most metabolic pathways are in a state of equilibrium and have a △G equal to zero.

Accepted Answer

A) True 
 B)False

Question 20

The hydrolysis of ATP to ADP has a △G°ʹ of -30 kJ/mol. If in an E. coli cell the concentrations of ATP, ADP and inorganic phosphate are 7.90 mM, 1.04 mM and 7.9 mM, respectively, which statement is true about the hydrolysis of ATP in the cell? Assume a temperature of 298 K. R = 8.315 J/K-mol)

Accepted Answer

A)  Hydrolysis can proceed spontaneously. 
B)  The hydrolysis is at equilibrium. 
C)  The formation of ATP from ADP is occurring more rapidly than the hydrolysis. 
D)  The hydrolysis is being allosterically controlled. 
A)  Hydrolysis can proceed spontaneously. 
B)  The hydrolysis is at equilibrium. 
C)  The formation of ATP from ADP is occurring more rapidly than the hydrolysis. 
D)  The hydrolysis is being allosterically controlled.

Exam 10: Introduction to Metabolism

The flow of material through a reaction pathway usually depends on .

The most biochemically complex organisms are .

What defines a near-equilibrium reaction?

ATP is classified as an energy-rich compound because

The standard potential for electron transfer can be related to the standard free-energy change for redox reactions by using

The presence of Mg2+ ions decreases the free energy released by the hydrolysis of ATP.

An organism that uses organic molecules as carbon sources and obtains energy by oxidizing inorganic molecules is aan) .

Which is usually the slowest way to regulate a reaction in a metabolic pathway?

Many dehydrogenases can be assayed by measuring the decrease of absorption of NAD+ or the increase of absorption of NADH.

Anabolic and catabolic reactions in eukaryotes can occur simultaneously in cells. This is possible because .

The ultimate product of complete oxidation of carbohydrates is .

When a reduction half-reaction is negative, positive), electrons flow to the more readily reduced substance which is negative, positive) in value.

Which statement does not explain why many biochemical processes are carried out via multi-step pathways rather than by single-step reactions or only a few steps)?

The conversion of glucose-1-phosphate to glucose-6-phosphate by the enzyme phosphoglucomutase has a △G°ʹ of -7.6 kJ/mol. Calculate the equilibrium constant for this reaction at 298 K and a pH of 7. R = 8.315 J/K-mol)

A chemical reaction with a negative enthalpy change and a negative entropy change .

The formation of acetyl CoA is driven to completion by

A distinct set of metabolic reactions is called a reaction .

Both NADH and NADPH are oxidized in cells, but NADH is more often used in specialized pathways to provide hydride ions for reductive reactions in metabolism.

Reactions of most metabolic pathways are in a state of equilibrium and have a △G equal to zero.

The hydrolysis of ATP to ADP has a △G°ʹ of -30 kJ/mol. If in an E. coli cell the concentrations of ATP, ADP and inorganic phosphate are 7.90 mM, 1.04 mM and 7.9 mM, respectively, which statement is true about the hydrolysis of ATP in the cell? Assume a temperature of 298 K. R = 8.315 J/K-mol)

Introduction to Biochemistry

Water

Amino Acids and the Primary Structures of Proteins

Proteins: Three-Dimensional Structure and Function

Properties of Enzymes

Mechanisms of Enzymes

Coenzymes and Vitamins

Carbohydrates

Lipids and Membranes

Glycolysis

Gluconeogenesis, the Pentose Phosphate Pathway, and Glycogen Metabolism

The Citric Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Nucleic Acids

Dna Replication, Repair, and Recombination

Transcription and Rna Processing

Protein Synthesis

Recombinant Dna Technology

Filters

The presence of Mg²⁺ions decreases the free energy released by the hydrolysis of ATP.

Many dehydrogenases can be assayed by measuring the decrease of absorption of NAD⁺or the increase of absorption of NADH.

The conversion of glucose-1-phosphate to glucose-6-phosphate by the enzyme phosphoglucomutase has a △G°^ʹof -7.6 kJ/mol. Calculate the equilibrium constant for this reaction at 298 K and a pH of 7. R = 8.315 J/K-mol)

The hydrolysis of ATP to ADP has a △G°^ʹof -30 kJ/mol. If in an E. coli cell the concentrations of ATP, ADP and inorganic phosphate are 7.90 mM, 1.04 mM and 7.9 mM, respectively, which statement is true about the hydrolysis of ATP in the cell? Assume a temperature of 298 K. R = 8.315 J/K-mol)