Question 1

Which statement is TRUE for glycogen phosphorylase b?

Accepted Answer

A)  It catalyzes a phosphorylytic cleavage of $\alpha$(1$\rightarrow$6) glycosidic bonds. 
B)  It catalyzes a hydrolytic cleavage of $\alpha$(1$\rightarrow$4) glycosidic bonds. 
C)  It is regulated both allosterically and via covalent modification. 
D)  It uses UDP-glucose as a substrate. 
E)  It is an important blood glucose sensor in myocytes. 
A)  It catalyzes a phosphorylytic cleavage of $\alpha$(1$\rightarrow$6) glycosidic bonds. 
B)  It catalyzes a hydrolytic cleavage of $\alpha$(1$\rightarrow$4) glycosidic bonds. 
C)  It is regulated both allosterically and via covalent modification. 
D)  It uses UDP-glucose as a substrate. 
E)  It is an important blood glucose sensor in myocytes.

Question 2

After ingestion of a carbohydrate-rich meal, the increased concentration of glucose in the blood is associated with many changes in the metabolism of humans. Which change would NOT be expected?

Accepted Answer

A)  a decrease in the secretion of glucagon from the pancreas 
B)  an increase in glycogen phosphorolysis 
C)  an increase in the levels of fructose 2,6-bisphosphate 
D)  activation of phosphorylase b kinase 
E)  All of these changes would be expected. 
A)  a decrease in the secretion of glucagon from the pancreas 
B)  an increase in glycogen phosphorolysis 
C)  an increase in the levels of fructose 2,6-bisphosphate 
D)  activation of phosphorylase b kinase 
E)  All of these changes would be expected.

Question 3

What is the predominant source of glucose circulating in the bloodstream of a normal individual who is asleep at 3 AM?

Accepted Answer

A)  catabolism of even-chained fatty acids 
B)  gluconeogenesis in the liver 
C)  phosphorolysis of muscle glycogen 
D)  glycogenolysis in the liver 
E)  dietary carbohydrates 
A)  catabolism of even-chained fatty acids 
B)  gluconeogenesis in the liver 
C)  phosphorolysis of muscle glycogen 
D)  glycogenolysis in the liver 
E)  dietary carbohydrates

Question 4

Which statement is NOT associated with controlling the rate of glycogen synthesis in myocytes?

Accepted Answer

A)  Insulin stimulates the translocation of GLUT 4 transporters to the plasma membrane. 
B)  Insulin induces the synthesis of hexokinase I. 
C)  Glucagon inhibits the activity of glycogen synthase via covalent modification. 
D)  Epinephrine activates PKA, resulting in an activation of glycogen phosphorylase kinase. 
E)  Insulin inhibits the activity of glycogen synthase kinase 3. 
A)  Insulin stimulates the translocation of GLUT 4 transporters to the plasma membrane. 
B)  Insulin induces the synthesis of hexokinase I. 
C)  Glucagon inhibits the activity of glycogen synthase via covalent modification. 
D)  Epinephrine activates PKA, resulting in an activation of glycogen phosphorylase kinase. 
E)  Insulin inhibits the activity of glycogen synthase kinase 3.

Question 5

Which statement regarding regulation of glycolysis and gluconeogenesis is FALSE?

Accepted Answer

A)  Phosphofructokinase-1 and fructose 1,6-bisphosphatase are prevented from forming a futile cycle by reversible covalent modification. 
B)  Hexokinase IV and glucose 6-phosphatase are transcriptionally regulated in hepatocytes. 
C)  Phosphofructokinase-1 and fructose 1,6-bisphosphatase are reciprocally regulated by the allosteric regulator, fructose 2,6-bisphosphate. 
D)  Binding of fructose 2,6-bisphosphate to phosphofructokinase-1 reduces the affinity of this enzyme for citrate. 
E)  The cellular concentration of fructose 2,6-bisphosphate is determined by a bifunctional enzyme that is hormonally regulated. 
A)  Phosphofructokinase-1 and fructose 1,6-bisphosphatase are prevented from forming a futile cycle by reversible covalent modification. 
B)  Hexokinase IV and glucose 6-phosphatase are transcriptionally regulated in hepatocytes. 
C)  Phosphofructokinase-1 and fructose 1,6-bisphosphatase are reciprocally regulated by the allosteric regulator, fructose 2,6-bisphosphate. 
D)  Binding of fructose 2,6-bisphosphate to phosphofructokinase-1 reduces the affinity of this enzyme for citrate. 
E)  The cellular concentration of fructose 2,6-bisphosphate is determined by a bifunctional enzyme that is hormonally regulated.

Question 6

Which enzyme is NOT regulated?

Accepted Answer

A)  hexokinase 
B)  pyruvate kinase 
C)  phosphofructokinase-1 
D)  glyceraldehyde-3-phosphate dehydrogenase (GAPDH) 
E)  All these enzymes are regulated. 
A)  hexokinase 
B)  pyruvate kinase 
C)  phosphofructokinase-1 
D)  glyceraldehyde-3-phosphate dehydrogenase (GAPDH) 
E)  All these enzymes are regulated.

Question 7

Which statement is NOT valid with respect to the enzyme adenylate kinase?

Accepted Answer

A)  The reversible reaction catalyzed by adenylate kinase is 2ADP $\nu$ ATP + AMP. 
B)  During a 100-meter sprint, adenylate kinase in myocytes catalyzes a biochemical reaction that provides some ATP. 
C)  Activated adenylate kinase catalyzes the reaction that generates the second messenger cAMP from ATP. 
D)  When cellular ATP is being used, adenylate kinase generates AMP, a signal of a low-energy state. 
E)  Adenylate kinase is a phosphotransferase enzyme that plays a critical role in cellular energy homeostasis. 
A)  The reversible reaction catalyzed by adenylate kinase is 2ADP $\nu$ ATP + AMP. 
B)  During a 100-meter sprint, adenylate kinase in myocytes catalyzes a biochemical reaction that provides some ATP. 
C)  Activated adenylate kinase catalyzes the reaction that generates the second messenger cAMP from ATP. 
D)  When cellular ATP is being used, adenylate kinase generates AMP, a signal of a low-energy state. 
E)  Adenylate kinase is a phosphotransferase enzyme that plays a critical role in cellular energy homeostasis.

Question 8

During exercise, glycogen in both liver and muscle cells can be converted to glucose metabolites for ATP generation in skeletal muscle. Do liver glycogen and muscle glycogen supply the same amount of ATP to skeletal muscles? Explain

Accepted Answer

No, liver glycogen and muscle glycogen d

Question 9

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

Accepted Answer

A)  phosphoglycerate kinase 
B)  GAP dehydrogenase 
C)  adenylate kinase 
D)  fructose 1-phosphate aldolase 
E)  phosphofructokinase-1 
A)  phosphoglycerate kinase 
B)  GAP dehydrogenase 
C)  adenylate kinase 
D)  fructose 1-phosphate aldolase 
E)  phosphofructokinase-1

Question 10

Starting from glucose, what is the net number of NTP molecules used in the synthesis of glycogen?

Accepted Answer

A)  zero 
B)  one 
C)  two 
D)  three 
E)  four 
A)  zero 
B)  one 
C)  two 
D)  three 
E)  four

Question 11

Muscle contraction is associated with elevated levels of cytosolic calcium. Which statement describes a consequence of this increase in calcium?

Accepted Answer

A)  Calcium is a divalent cation, which binds to ATP and reduces electrostatic repulsion between the phosphates. Glycogen is broken down to compensate for the decreased energy available from ATP hydrolysis. 
B)  An increased level of calcium is associated with an increase in glycogen breakdown, as calcium is an allosteric activator of glycogen phosphorylase. 
C)  Calcium activates phosphoprotein phosphatase 1, which in turn will stimulate glycogen synthesis by dephosphorylating phosphorylase b. 
D)  An increased level of calcium is associated with an increase in glycogen breakdown, as calcium is an allosteric activator of phosphorylase b kinase. 
E)  All the answers are correct. 
A)  Calcium is a divalent cation, which binds to ATP and reduces electrostatic repulsion between the phosphates. Glycogen is broken down to compensate for the decreased energy available from ATP hydrolysis. 
B)  An increased level of calcium is associated with an increase in glycogen breakdown, as calcium is an allosteric activator of glycogen phosphorylase. 
C)  Calcium activates phosphoprotein phosphatase 1, which in turn will stimulate glycogen synthesis by dephosphorylating phosphorylase b. 
D)  An increased level of calcium is associated with an increase in glycogen breakdown, as calcium is an allosteric activator of phosphorylase b kinase. 
E)  All the answers are correct.

Question 12

What will be the net yield of ATP (per glucose unit) starting from glycogen and ending at pyruvate?

Accepted Answer

A)  1 ATP 
B)  2 ATP 
C)  3 ATP 
D)  4 ATP 
E)  5 ATP 
A)  1 ATP 
B)  2 ATP 
C)  3 ATP 
D)  4 ATP 
E)  5 ATP

Question 13

Which factor affects the activity of glucokinase in hepatocytes?

Accepted Answer

A)  transcriptional regulation 
B)  subcellular localisation 
C)  association with a regulatory protein 
D)  transcriptional regulation and subcellular localisation 
E)  All of the answers are correct. 
A)  transcriptional regulation 
B)  subcellular localisation 
C)  association with a regulatory protein 
D)  transcriptional regulation and subcellular localisation 
E)  All of the answers are correct.

Question 14

Does the regulation of PFK-1 affect the activity of hexokinase I in muscle tissue? Explain your reasoning.

Accepted Answer

The regulation of PFK-1 does affect the

Question 15

Which statement does NOT describe a characteristic of phosphoprotein phosphorylase-1 (PP1)?

Accepted Answer

A)  PP1 can be phosphorylated by protein kinase A (PK
A) . 
B)  PP1 can dephosphorylate glycogen phosphorylase, glycogen synthase, and phosphorylase kinase. 
C)  PP1 is allosterically activated by glucose-6-phosphate. 
D)  PP1 is inhibited by activated glycogen phosphorylase 
E)  PP1 is phosphorylated by glycogen synthase kinase-3 (GSK3). 
A)  PP1 can be phosphorylated by protein kinase A (PK
A) . 
B)  PP1 can dephosphorylate glycogen phosphorylase, glycogen synthase, and phosphorylase kinase. 
C)  PP1 is allosterically activated by glucose-6-phosphate. 
D)  PP1 is inhibited by activated glycogen phosphorylase 
E)  PP1 is phosphorylated by glycogen synthase kinase-3 (GSK3).

Question 16

For an enzyme to effectively change its activity in response to a change in substrate concentration, it is MOST favorable for:

Accepted Answer

A)  Km to be less than cellular substrate concentrations. 
B)  Km to be equal to cellular substrate concentrations. 
C)  Km to be greater than cellular substrate concentrations. 
D)  Vmax to be at the diffusion limit. 
E)  the substrate to also be an allosteric effector. 
A)  Km to be less than cellular substrate concentrations. 
B)  Km to be equal to cellular substrate concentrations. 
C)  Km to be greater than cellular substrate concentrations. 
D)  Vmax to be at the diffusion limit. 
E)  the substrate to also be an allosteric effector.

Question 17

Order the steps leading to glycogen breakdown resulting from the stimulation of liver cells by glucagon.
1) Activation of protein kinase A (PKA)
2) cAMP levels rise
3) Phosphorylation of phosphorylase b
4) Phosphorylation of phosphorylase b kinase
5) Stimulation of adenyl cyclase

Accepted Answer

The steps leading to glycogen breakdown

Question 18

Which statement is TRUE for the reciprocal regulation of phosphofructokinase-1 (PFK-1) and fructose 1,6-bisphosphatase (FBPase-1)?

Accepted Answer

A)  Fructose 2,6-bisphosphate inhibits FBPase-1 and activates PFK-1. 
B)  Fructose 2,6-bisphosphate inhibits PFK-1 and activates FBPase-1. 
C)  Fructose 1,6-bisphosphate inhibits FBPase-1 and activates PFK-1. 
D)  Fructose 1,6-bisphosphate inhibits PFK-1 and activates FBPase-1. 
A)  Fructose 2,6-bisphosphate inhibits FBPase-1 and activates PFK-1. 
B)  Fructose 2,6-bisphosphate inhibits PFK-1 and activates FBPase-1. 
C)  Fructose 1,6-bisphosphate inhibits FBPase-1 and activates PFK-1. 
D)  Fructose 1,6-bisphosphate inhibits PFK-1 and activates FBPase-1.

Question 19

Which statement is TRUE for "far from equilibrium" reactions in a cell?

Accepted Answer

A)  They are irreversible under all conditions. 
B)  Their standard free-energy changes are typically large and positive. 
C)  They are common control points of regulation in a metabolic pathway. 
D)  All of the statements are true. 
E)  None of the statements is true. 
A)  They are irreversible under all conditions. 
B)  Their standard free-energy changes are typically large and positive. 
C)  They are common control points of regulation in a metabolic pathway. 
D)  All of the statements are true. 
E)  None of the statements is true.

Question 20

Which statement is TRUE of the glycogen branching enzyme?

Accepted Answer

A)  It catalyzes glycogen degradation by removing glucose from the branch points. 
B)  It catalyzes the formation of an $\alpha$ 1-4 linkages during glycogen synthesis. 
C)  It catalyzes the addition of a glucose molecule to glycogenin. 
D)  It is allosterically regulated by fructose 2,6-bisphosphate. 
E)  It is an enzyme that belongs to a family of transferases. 
A)  It catalyzes glycogen degradation by removing glucose from the branch points. 
B)  It catalyzes the formation of an $\alpha$ 1-4 linkages during glycogen synthesis. 
C)  It catalyzes the addition of a glucose molecule to glycogenin. 
D)  It is allosterically regulated by fructose 2,6-bisphosphate. 
E)  It is an enzyme that belongs to a family of transferases.

Exam 15: Principles of Metabolic Regulation

Which statement is TRUE for glycogen phosphorylase b?

After ingestion of a carbohydrate-rich meal, the increased concentration of glucose in the blood is associated with many changes in the metabolism of humans. Which change would NOT be expected?

What is the predominant source of glucose circulating in the bloodstream of a normal individual who is asleep at 3 AM?

Which statement is NOT associated with controlling the rate of glycogen synthesis in myocytes?

Which statement regarding regulation of glycolysis and gluconeogenesis is FALSE?

Which enzyme is NOT regulated?

Which statement is NOT valid with respect to the enzyme adenylate kinase?

During exercise, glycogen in both liver and muscle cells can be converted to glucose metabolites for ATP generation in skeletal muscle. Do liver glycogen and muscle glycogen supply the same amount of ATP to skeletal muscles? Explain

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

Starting from glucose, what is the net number of NTP molecules used in the synthesis of glycogen?

Muscle contraction is associated with elevated levels of cytosolic calcium. Which statement describes a consequence of this increase in calcium?

What will be the net yield of ATP (per glucose unit) starting from glycogen and ending at pyruvate?

Which factor affects the activity of glucokinase in hepatocytes?

Does the regulation of PFK-1 affect the activity of hexokinase I in muscle tissue? Explain your reasoning.

Which statement does NOT describe a characteristic of phosphoprotein phosphorylase-1 (PP1)?

For an enzyme to effectively change its activity in response to a change in substrate concentration, it is MOST favorable for:

Order the steps leading to glycogen breakdown resulting from the stimulation of liver cells by glucagon. 1) Activation of protein kinase A (PKA) 2) cAMP levels rise 3) Phosphorylation of phosphorylase b 4) Phosphorylation of phosphorylase b kinase 5) Stimulation of adenyl cyclase

Which statement is TRUE for the reciprocal regulation of phosphofructokinase-1 (PFK-1) and fructose 1,6-bisphosphatase (FBPase-1)?

Which statement is TRUE for "far from equilibrium" reactions in a cell?

Which statement is TRUE of the glycogen branching enzyme?

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

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