Question 1

Briefly outline the pathway by which glucose activates the synthesis of pyruvate kinase.

Accepted Answer

Glucose metabolism is a complex process

Question 2

Reaction steps that are far from equilibrium are good control points in metabolic pathways because:

Accepted Answer

A)  the net flux through those steps is easily reversed. 
B)  the rate differences between the forward and reverse steps are often small. 
C)  these reactions occur most frequently in the cell. 
D)  these reactions are highly endergonic. 
E)  these reactions are highly exergonic. 
A)  the net flux through those steps is easily reversed. 
B)  the rate differences between the forward and reverse steps are often small. 
C)  these reactions occur most frequently in the cell. 
D)  these reactions are highly endergonic. 
E)  these reactions are highly exergonic.

Question 3

Which substance activates glycogen synthase b in liver?

Accepted Answer

A)  glucagon 
B)  insulin 
C)  glucose 6-phosphate 
D)  both insulin and glucose 6-phosphate 
E)  both glucagon and glucose 6-phosphate 
A)  glucagon 
B)  insulin 
C)  glucose 6-phosphate 
D)  both insulin and glucose 6-phosphate 
E)  both glucagon and glucose 6-phosphate

Question 4

Many of the steps in the pathways described in this chapter are essentially irreversible (for A $\rightarrow$  B $\Delta$G << 0). As a result, if the cell wants to carry out the reverse transformation, it must use a different pathway to go from B  $\rightarrow$  A. For each of the enzymes on the left, pick the enzyme on the right that carries out the reverse transformation (not necessarily the reverse reaction).

Accepted Answer

The question seems to be related to meta

Question 5

Which statement accurately describes the effect of insulin on the expression of the gene for glucose 6-phosphatase?

Accepted Answer

A)  Insulin triggers the phosphorylation of PKB, which then phosphorylates FOXO-1. Phosphorylation of FOXO-1 causes a decrease in its degradation by the proteasome, which is associated with an increase in the expression of the gene for glucose 6-phosphatase. 
B)  Insulin activates PKB by phosphorylation, which then phosphorylates FOXO-1. Phosphorylation of FOXO-1 causes an increase in its degradation by the proteasome, which is associated with an increase in the expression of the gene for glucose 6-phosphatase. 
C)  Insulin leads to the activation of PKA, which then phosphorylates FOXO-1. Phosphorylation of FOXO-1 causing a decrease in its degradation by the proteasome, which is associated with a decrease in the expression of the gene for glucose 6-phosphatase. 
D)  Insulin leads to the activation of PKB, which then phosphorylates FOXO-1. Phosphorylation of FOXO-1 causing an increase in its degradation by the proteasome, which is associated with a decrease in the expression of the gene for glucose 6-phosphatase. 
E)  Insulin activates phosphoprotein phosphatase, which then dephosphorylates FOXO-1. Dephosphorylation of FOXO-1 causes a decrease in its degradation by the proteasome and an increase in the expression of the gene for glucose 6-phosphatase. 
A)  Insulin triggers the phosphorylation of PKB, which then phosphorylates FOXO-1. Phosphorylation of FOXO-1 causes a decrease in its degradation by the proteasome, which is associated with an increase in the expression of the gene for glucose 6-phosphatase. 
B)  Insulin activates PKB by phosphorylation, which then phosphorylates FOXO-1. Phosphorylation of FOXO-1 causes an increase in its degradation by the proteasome, which is associated with an increase in the expression of the gene for glucose 6-phosphatase. 
C)  Insulin leads to the activation of PKA, which then phosphorylates FOXO-1. Phosphorylation of FOXO-1 causing a decrease in its degradation by the proteasome, which is associated with a decrease in the expression of the gene for glucose 6-phosphatase. 
D)  Insulin leads to the activation of PKB, which then phosphorylates FOXO-1. Phosphorylation of FOXO-1 causing an increase in its degradation by the proteasome, which is associated with a decrease in the expression of the gene for glucose 6-phosphatase. 
E)  Insulin activates phosphoprotein phosphatase, which then dephosphorylates FOXO-1. Dephosphorylation of FOXO-1 causes a decrease in its degradation by the proteasome and an increase in the expression of the gene for glucose 6-phosphatase.

Question 6

Show the reaction catalyzed by glycogen synthase.

Accepted Answer

Glycogen synthase is an enzyme that play

Question 7

Which compound is NOT associated (in some way) with glycogen granules in the cytosol of myocytes?

Accepted Answer

A)  glycogenin 
B)  glucose 
C)  inhibitor 1 
D)  adenylate kinase 
E)  calmodulin 
A)  glycogenin 
B)  glucose 
C)  inhibitor 1 
D)  adenylate kinase 
E)  calmodulin

Question 8

Glucokinase (hexokinase IV) differs from hexokinase (hexokinase I):

Accepted Answer

A)  by having a higher affinity for glucose and not being inhibited by high levels of glucose. 
B)  by requiring larger concentrations of glucose before reaching maximal activity. 
C)  to allow the liver to export free glucose to the bloodstream when blood sugar levels drop. 
D)  so that the liver does not compete with other tissues for glucose when glucose levels are high. 
E)  to allow the pancreas to trigger insulin release when blood sugar levels are low. 
A)  by having a higher affinity for glucose and not being inhibited by high levels of glucose. 
B)  by requiring larger concentrations of glucose before reaching maximal activity. 
C)  to allow the liver to export free glucose to the bloodstream when blood sugar levels drop. 
D)  so that the liver does not compete with other tissues for glucose when glucose levels are high. 
E)  to allow the pancreas to trigger insulin release when blood sugar levels are low.

Question 9

There is reciprocal regulation of glycolytic and gluconeogenic reactions interconverting fructose-6-phosphate and fructose-1,6-bisphosphate. Which statement about this regulation is NOT correct?

Accepted Answer

A)  Fructose-2,6-bisphosphate activates phosphofructokinase-1. 
B)  Fructose-2,6-bisphosphate inhibits fructose-1,6-bisphosphatase. 
C)  The fructose-1,6-bisphosphatase reaction is exergonic. 
D)  The phosphofructokinase-1 reaction is endergonic. 
E)  This regulation allows control of the direction of net metabolite flow through the pathway. 
A)  Fructose-2,6-bisphosphate activates phosphofructokinase-1. 
B)  Fructose-2,6-bisphosphate inhibits fructose-1,6-bisphosphatase. 
C)  The fructose-1,6-bisphosphatase reaction is exergonic. 
D)  The phosphofructokinase-1 reaction is endergonic. 
E)  This regulation allows control of the direction of net metabolite flow through the pathway.

Question 10

Which pairing CORRECTLY matches an enzyme with its effector?

Accepted Answer

A)  phosphofructokinase-1/fructose 1,6-bisphosphate 
B)  phosphofructokinase-2/fructose 2,6-bisphosphate 
C)  fructose 1,6-bisphosphatase/fructose 1,6-bisphosphate 
D)  fructose 1,6-bisphosphatase/fructose 2,6-bisphosphate 
E)  fructose 2,6-bisphosphatase/fructose 2,6-bisphosphate 
A)  phosphofructokinase-1/fructose 1,6-bisphosphate 
B)  phosphofructokinase-2/fructose 2,6-bisphosphate 
C)  fructose 1,6-bisphosphatase/fructose 1,6-bisphosphate 
D)  fructose 1,6-bisphosphatase/fructose 2,6-bisphosphate 
E)  fructose 2,6-bisphosphatase/fructose 2,6-bisphosphate

Question 11

Glycogen synthase kinase-3 inhibitors are being tested for their usefulness in the treatment of type 2 diabetes. Predict the role that these inhibitors may play in the treatment of this disease.

Accepted Answer

Glycogen synthase kinase-3 (GSK-3) inhib

Question 12

Metabolic pathways are said to operate in a steady state. Which process does NOT contribute to this?

Accepted Answer

A)  Most biological reactions are reversible under normal cellular conditions. 
B)  Key reactions at the beginning and end of a pathway are often regulated synchronously. 
C)  Catabolic pathways are active when cellular energy levels are low. 
D)  Reversible reactions proceed to equilibrium. 
A)  Most biological reactions are reversible under normal cellular conditions. 
B)  Key reactions at the beginning and end of a pathway are often regulated synchronously. 
C)  Catabolic pathways are active when cellular energy levels are low. 
D)  Reversible reactions proceed to equilibrium.

Question 13

Although in higher animals fats are the most efficient storage form of "free-energy," not all ingested carbohydrate is converted to fat. Some is stored in the form of glycogen. Which statement does NOT apply to the metabolic benefits of storing "free-energy" in the form of glycogen?

Accepted Answer

A)  Glycogen can be rapidly catabolized because its structure allows for several catabolic enzymes to work in parallel. 
B)  Glycogen in skeletal muscle can be mobilized under anaerobic conditions, whereas products of fatty acid catabolism cannot. 
C)  In contrast to glycogen, the products of fatty acid catabolism are not gluconeogenic. 
D)  Erythrocytes have an absolute requirement for glucose and cannot use any product of fat metabolism for their energy needs. 
E)  Glycogen molecules are highly hydrated. 
A)  Glycogen can be rapidly catabolized because its structure allows for several catabolic enzymes to work in parallel. 
B)  Glycogen in skeletal muscle can be mobilized under anaerobic conditions, whereas products of fatty acid catabolism cannot. 
C)  In contrast to glycogen, the products of fatty acid catabolism are not gluconeogenic. 
D)  Erythrocytes have an absolute requirement for glucose and cannot use any product of fat metabolism for their energy needs. 
E)  Glycogen molecules are highly hydrated.

Question 14

Under what circumstances does the bifunctional protein phosphofructokinase-2/fructose 2,6-bisphosphatase (PFK-2/FBPase-2) become phosphorylated, and what are the consequences of its phosphorylation to the glycolytic and gluconeogenic pathways?

Accepted Answer

The bifunctional protein phosphofructoki

Question 15

Which type of mechanism is NOT known to play a role in the reversible alteration of enzyme activity?

Accepted Answer

A)  activation by cleavage of an inactive zymogen 
B)  allosteric response to a regulatory molecule 
C)  alteration of the synthesis or degradation rate of an enzyme 
D)  covalent modification of the enzyme 
E)  interactions between catalytic and regulatory subunits 
A)  activation by cleavage of an inactive zymogen 
B)  allosteric response to a regulatory molecule 
C)  alteration of the synthesis or degradation rate of an enzyme 
D)  covalent modification of the enzyme 
E)  interactions between catalytic and regulatory subunits

Question 16

Gluconeogenesis must use "bypass reactions" to circumvent three reactions in the glycolytic pathway that are highly exergonic and essentially irreversible. Reactions carried out by which three of the enzymes listed must be bypassed in the gluconeogenic pathway? 1) Hexokinase
2) Phosphoglycerate kinase
3) Phosphofructokinase-1
4) Pyruvate kinase
5) Triosephosphate isomerase

Accepted Answer

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

Question 17

An increase in which compound leads to the dephosphorylation and activation of phosphofructokinase-2?

Accepted Answer

A)  glucagon 
B)  xyulose-5-phosphate 
C)  pyruvate 
D)  citrate 
E)  ADP 
A)  glucagon 
B)  xyulose-5-phosphate 
C)  pyruvate 
D)  citrate 
E)  ADP

Question 18

Aside from maintaining the integrity of its hereditary material, the MOST important general metabolic concern of a cell is:

Accepted Answer

A)  keeping its glucose levels high. 
B)  maintaining a constant supply and concentration of ATP. 
C)  preserving its ability to carry out oxidative phosphorylation. 
D)  protecting its enzymes from rapid degradation. 
E)  running all its major metabolic pathways at maximum efficiency. 
A)  keeping its glucose levels high. 
B)  maintaining a constant supply and concentration of ATP. 
C)  preserving its ability to carry out oxidative phosphorylation. 
D)  protecting its enzymes from rapid degradation. 
E)  running all its major metabolic pathways at maximum efficiency.

Question 19

Which isozyme of lactate dehydrogenase has the LOWEST Km value for the reduction of pyruvate in skeletal muscle?

Accepted Answer

A) 	LDH1 
B) 	LDH2 
C) 	LDH3 
D) 	LDH4 
A) 	LDH1 
B) 	LDH2 
C) 	LDH3 
D) 	LDH4

Question 20

Which metabolic effect is associated with AMP-activated protein kinase (AMPK)?

Accepted Answer

A)  When activated, AMPK stimulates insulin release from the pancreas. 
B)  When activated, AMPK activates fructose 2,6-bisphosphatase. 
C)  When activated, AMPK stimulates glucose uptake in cardiac and skeletal muscle. 
D)  When activated, AMPK both activates fructose 2,6-bisphosphatase and stimulates glucose uptake in cardiac and skeletal muscle. 
E)  None of the answers is correct. 
A)  When activated, AMPK stimulates insulin release from the pancreas. 
B)  When activated, AMPK activates fructose 2,6-bisphosphatase. 
C)  When activated, AMPK stimulates glucose uptake in cardiac and skeletal muscle. 
D)  When activated, AMPK both activates fructose 2,6-bisphosphatase and stimulates glucose uptake in cardiac and skeletal muscle. 
E)  None of the answers is correct.

Exam 15: Principles of Metabolic Regulation

Briefly outline the pathway by which glucose activates the synthesis of pyruvate kinase.

Reaction steps that are far from equilibrium are good control points in metabolic pathways because:

Which substance activates glycogen synthase b in liver?

Which statement accurately describes the effect of insulin on the expression of the gene for glucose 6-phosphatase?

Show the reaction catalyzed by glycogen synthase.

Which compound is NOT associated (in some way) with glycogen granules in the cytosol of myocytes?

Glucokinase (hexokinase IV) differs from hexokinase (hexokinase I):

There is reciprocal regulation of glycolytic and gluconeogenic reactions interconverting fructose-6-phosphate and fructose-1,6-bisphosphate. Which statement about this regulation is NOT correct?

Which pairing CORRECTLY matches an enzyme with its effector?

Glycogen synthase kinase-3 inhibitors are being tested for their usefulness in the treatment of type 2 diabetes. Predict the role that these inhibitors may play in the treatment of this disease.

Metabolic pathways are said to operate in a steady state. Which process does NOT contribute to this?

Although in higher animals fats are the most efficient storage form of "free-energy," not all ingested carbohydrate is converted to fat. Some is stored in the form of glycogen. Which statement does NOT apply to the metabolic benefits of storing "free-energy" in the form of glycogen?

Under what circumstances does the bifunctional protein phosphofructokinase-2/fructose 2,6-bisphosphatase (PFK-2/FBPase-2) become phosphorylated, and what are the consequences of its phosphorylation to the glycolytic and gluconeogenic pathways?

Which type of mechanism is NOT known to play a role in the reversible alteration of enzyme activity?

An increase in which compound leads to the dephosphorylation and activation of phosphofructokinase-2?

Aside from maintaining the integrity of its hereditary material, the MOST important general metabolic concern of a cell is:

Which isozyme of lactate dehydrogenase has the LOWEST Km value for the reduction of pyruvate in skeletal muscle?

Which metabolic effect is associated with AMP-activated protein kinase (AMPK)?

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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