Question 1

What are the regulatory implications for the cell with regard to ATP and AMP, given that the former are generally high, and the latter are low?

Accepted Answer

In cellular metabolism, ATP (adenosine t

Question 2

If the mass action ratio, Q, for a reaction under cellular conditions is larger than the equilibrium constant, Keq, then the reaction will:

Accepted Answer

A)  be at equilibrium. 
B)  go backward and be endergonic. 
C)  go backward and be exergonic. 
D)  go forward and be endergonic. 
E)  go forward and be exergonic. 
A)  be at equilibrium. 
B)  go backward and be endergonic. 
C)  go backward and be exergonic. 
D)  go forward and be endergonic. 
E)  go forward and be exergonic.

Question 3

Cellular isozymes of pyruvate kinase are allosterically inhibited by:

Accepted Answer

A)  high concentrations of AMP. 
B)  high concentrations of ATP. 
C)  high concentrations of citrate. 
D)  low concentrations of acetyl-CoA. 
E)  low concentrations of ATP. 
A)  high concentrations of AMP. 
B)  high concentrations of ATP. 
C)  high concentrations of citrate. 
D)  low concentrations of acetyl-CoA. 
E)  low concentrations of ATP.

Question 4

The elasticity coefficient for an enzyme in a multistep pathway depends on:

Accepted Answer

A)  the concentration of the enzyme itself. 
B)  the levels of regulatory molecules. 
C)  the amounts of substrate molecules present at each step. 
D)  both the concentration of the enzyme itself and the amounts of substrate molecules present at each step. 
E)  both the levels of regulatory molecules and the amounts of substrate molecules present at each step. 
A)  the concentration of the enzyme itself. 
B)  the levels of regulatory molecules. 
C)  the amounts of substrate molecules present at each step. 
D)  both the concentration of the enzyme itself and the amounts of substrate molecules present at each step. 
E)  both the levels of regulatory molecules and the amounts of substrate molecules present at each step.

Question 5

Which enzyme-catalyzed reaction is MOST sensitive to changes in the concentration of its reactants under physiological conditions?

Accepted Answer

A)  hexokinase 
B)  pyruvate kinase 
C)  adenylate kinase 
D)  glucose-6-phosphatase 
E)  phosphofructokinase-1 
A)  hexokinase 
B)  pyruvate kinase 
C)  adenylate kinase 
D)  glucose-6-phosphatase 
E)  phosphofructokinase-1

Question 6

Which statement is TRUE of glycogen synthesis and breakdown?

Accepted Answer

A)  Phosphorylation activates the enzyme responsible for breakdown, and inactivates the synthetic enzyme. 
B)  Synthesis is catalyzed by the same enzyme that catalyzes breakdown. 
C)  The glycogen molecule "grows" at its reducing end. 
D)  The immediate product of glycogen breakdown is free glucose. 
E)  Under normal circumstances, glycogen synthesis and glycogen breakdown occur simultaneously and at high rates. 
A)  Phosphorylation activates the enzyme responsible for breakdown, and inactivates the synthetic enzyme. 
B)  Synthesis is catalyzed by the same enzyme that catalyzes breakdown. 
C)  The glycogen molecule "grows" at its reducing end. 
D)  The immediate product of glycogen breakdown is free glucose. 
E)  Under normal circumstances, glycogen synthesis and glycogen breakdown occur simultaneously and at high rates.

Question 7

Which statement describes a possible fate for glucose 1-phosphate in skeletal muscle?

Accepted Answer

A)  Glucose 1-phosphate can enter glycolysis after conversion to glucose 6-phosphate. 
B)  Glucose 1-phosphate cannot enter the pentose phosphate pathway after conversion to glucose 6-phosphate. 
C)  Glucose 1-phosphate can be used to replenish blood glucose. 
D)  Glucose 1-phosphate can be used to replenish blood glucose or enter glycolysis after conversion to glucose 6-phosphate. 
E)  All of the answers are correct. 
A)  Glucose 1-phosphate can enter glycolysis after conversion to glucose 6-phosphate. 
B)  Glucose 1-phosphate cannot enter the pentose phosphate pathway after conversion to glucose 6-phosphate. 
C)  Glucose 1-phosphate can be used to replenish blood glucose. 
D)  Glucose 1-phosphate can be used to replenish blood glucose or enter glycolysis after conversion to glucose 6-phosphate. 
E)  All of the answers are correct.

Question 8

In mammalian liver, glucose-1-phosphate, the product of glycogen phosphorylase, can enter glycolysis or replenish blood glucose. Describe the reactions by which these two processes are carried out.

Accepted Answer

Glucose-1-phosphate, the product of glyc

Question 9

Name three glycolytic enzymes whose expression is are up-regulated in response to insulin and two gluconeogenic enzymes whose expression is down-regulated in response to insulin.

Accepted Answer

Three glycolytic enzymes whose expressio

Question 10

Which enzyme does NOT play a role in glycogen metabolism?

Accepted Answer

A)  glucose-6-phosphatase 
B)  fructose 1,6-bisphosphatase 
C)  glycosyl-(4$\rightarrow$6) transferase 
D)  protein phosphatase 1 
E)  phosphoglucomutase 
A)  glucose-6-phosphatase 
B)  fructose 1,6-bisphosphatase 
C)  glycosyl-(4$\rightarrow$6) transferase 
D)  protein phosphatase 1 
E)  phosphoglucomutase

Question 11

Glycogen storage disease (GSD) type 1a is associated with mutations in glucose 6-phosphatase. There are other forms of GSD type I. Which protein is likely mutated in these other forms of GSD?

Accepted Answer

A)  G6P transporter (T1) 
B)  Pi transporter (T3) 
C)  glucose transporter (GLUT2) 
D)  T1 and T3 
E)  T1, T3, and GLUT2 
A)  G6P transporter (T1) 
B)  Pi transporter (T3) 
C)  glucose transporter (GLUT2) 
D)  T1 and T3 
E)  T1, T3, and GLUT2

Question 12

Which method of directly regulates PFK-I?

Accepted Answer

A)  feedback inhibition by fructose 2,6-bisphosphate 
B)  feed forward activation by phosphoenolpyruvate 
C)  allosteric activation by AMP 
D)  its phosphorylation in response to glucagon signaling 
E)  allosteric activation by citrate 
A)  feedback inhibition by fructose 2,6-bisphosphate 
B)  feed forward activation by phosphoenolpyruvate 
C)  allosteric activation by AMP 
D)  its phosphorylation in response to glucagon signaling 
E)  allosteric activation by citrate

Question 13

Which statement is FALSE with respect to near-equilibrium metabolic reactions?

Accepted Answer

A)  Near-equilibrium reactions have a free-energy change near zero. 
B)  Near-equilibrium reactions operate nonenzymatically in vivo. 
C)  Near-equilibrium reactions are dependent on the concentration of the products. 
D)  Near-equilibrium reactions are not usually a control point in a metabolic pathway. 
E)  All of the statements are false. 
A)  Near-equilibrium reactions have a free-energy change near zero. 
B)  Near-equilibrium reactions operate nonenzymatically in vivo. 
C)  Near-equilibrium reactions are dependent on the concentration of the products. 
D)  Near-equilibrium reactions are not usually a control point in a metabolic pathway. 
E)  All of the statements are false.

Question 14

Is glycogen phosphorylase activated, inhibited, or unaffected in response to a glucagon signal in skeletal muscle?

Accepted Answer

A)  activated 
B)  inhibited 
C)  unaffected 
A)  activated 
B)  inhibited 
C)  unaffected

Question 15

Is glycogen phosphorylase activated, inhibited, or unaffected in response to an insulin signal in skeletal muscle?

Accepted Answer

A)  activated 
B)  inhibited 
C)  unaffected 
A)  activated 
B)  inhibited 
C)  unaffected

Question 16

Diagram the pathway from glucose to glycogen; show the participation of cofactors and name the enzymes involved.

Accepted Answer

The pathway from glucose to glycogen inv

Question 17

Which factor is NOT involved in up-regulating the transcription of glycolytic or gluconeogenic enzymes?

Accepted Answer

A)  phosphofructokinase-2 
B)  carbohydrate response element binding protein 
C)  sterol response element binding protein 
D)  cAMP response element binding protein 
E)  FOXO1 
A)  phosphofructokinase-2 
B)  carbohydrate response element binding protein 
C)  sterol response element binding protein 
D)  cAMP response element binding protein 
E)  FOXO1

Question 18

Which statement about gluconeogenesis in animal cells is TRUE?

Accepted Answer

A)  A rise in the cellular level of fructose-2,6-bisphosphate stimulates the rate of gluconeogenesis. 
B)  An animal fed a large excess of fat in the diet will convert any fat not needed for energy production into glycogen to be stored for later use. 
C)  The conversion of fructose 1,6-bisphosphate to fructose 6-phosphate is not catalyzed by phosphofructokinase-1, the enzyme involved in glycolysis. 
D)  The conversion of glucose 6-phosphate to glucose is catalyzed by hexokinase, the same enzyme involved in glycolysis. 
E)  The conversion of phosphoenol pyruvate to 2-phosphoglycerate occurs in two steps, including a carboxylation. 
A)  A rise in the cellular level of fructose-2,6-bisphosphate stimulates the rate of gluconeogenesis. 
B)  An animal fed a large excess of fat in the diet will convert any fat not needed for energy production into glycogen to be stored for later use. 
C)  The conversion of fructose 1,6-bisphosphate to fructose 6-phosphate is not catalyzed by phosphofructokinase-1, the enzyme involved in glycolysis. 
D)  The conversion of glucose 6-phosphate to glucose is catalyzed by hexokinase, the same enzyme involved in glycolysis. 
E)  The conversion of phosphoenol pyruvate to 2-phosphoglycerate occurs in two steps, including a carboxylation.

Question 19

Which statement is TRUE for glycogen granules in hepatocytes?

Accepted Answer

A)  Hepatic glycogen granules account for approximately 1% to 2% of the weight of the liver. 
B)  Each particle may contain up to 55,000 glucose molecules. 
C)  Glycogen granules cluster together, forming $\alpha$-rosettes that become visible after a 24-hour fast. 
D)  All of the statements are true. 
E)  None of the statements is true. 
A)  Hepatic glycogen granules account for approximately 1% to 2% of the weight of the liver. 
B)  Each particle may contain up to 55,000 glucose molecules. 
C)  Glycogen granules cluster together, forming $\alpha$-rosettes that become visible after a 24-hour fast. 
D)  All of the statements are true. 
E)  None of the statements is true.

Question 20

Epinephrine binding to $\beta$-adrenergic receptors on hepatocytes causes the eventual activation of protein kinase A. Which enzyme is NOT a substrate for protein kinase A?

Accepted Answer

A)  phosphorylase b 
B)  phosphorylase b kinase 
C)  glycogen synthase 
D)  phosphofructokinase-2 
E)  pyruvate kinase 
A)  phosphorylase b 
B)  phosphorylase b kinase 
C)  glycogen synthase 
D)  phosphofructokinase-2 
E)  pyruvate kinase

Exam 15: Principles of Metabolic Regulation

What are the regulatory implications for the cell with regard to ATP and AMP, given that the former are generally high, and the latter are low?

If the mass action ratio, Q, for a reaction under cellular conditions is larger than the equilibrium constant, Keq, then the reaction will:

Cellular isozymes of pyruvate kinase are allosterically inhibited by:

The elasticity coefficient for an enzyme in a multistep pathway depends on:

Which enzyme-catalyzed reaction is MOST sensitive to changes in the concentration of its reactants under physiological conditions?

Which statement is TRUE of glycogen synthesis and breakdown?

Which statement describes a possible fate for glucose 1-phosphate in skeletal muscle?

In mammalian liver, glucose-1-phosphate, the product of glycogen phosphorylase, can enter glycolysis or replenish blood glucose. Describe the reactions by which these two processes are carried out.

Name three glycolytic enzymes whose expression is are up-regulated in response to insulin and two gluconeogenic enzymes whose expression is down-regulated in response to insulin.

Which enzyme does NOT play a role in glycogen metabolism?

Glycogen storage disease (GSD) type 1a is associated with mutations in glucose 6-phosphatase. There are other forms of GSD type I. Which protein is likely mutated in these other forms of GSD?

Which method of directly regulates PFK-I?

Which statement is FALSE with respect to near-equilibrium metabolic reactions?

Is glycogen phosphorylase activated, inhibited, or unaffected in response to a glucagon signal in skeletal muscle?

Is glycogen phosphorylase activated, inhibited, or unaffected in response to an insulin signal in skeletal muscle?

Diagram the pathway from glucose to glycogen; show the participation of cofactors and name the enzymes involved.

Which factor is NOT involved in up-regulating the transcription of glycolytic or gluconeogenic enzymes?

Which statement about gluconeogenesis in animal cells is TRUE?

Which statement is TRUE for glycogen granules in hepatocytes?

Epinephrine binding to β\betaβ -adrenergic receptors on hepatocytes causes the eventual activation of protein kinase A. Which enzyme is NOT a substrate for protein kinase A?

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

Bioenergetics and Biochemical Reaction Types

Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

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

If the mass action ratio, Q, for a reaction under cellular conditions is larger than the equilibrium constant, K_eq, then the reaction will:

Epinephrine binding to $\beta$ -adrenergic receptors on hepatocytes causes the eventual activation of protein kinase A. Which enzyme is NOT a substrate for protein kinase A?