Question 1

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.

Question 2

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.

Question 3

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 4

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

Question 5

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.

Question 6

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.

Question 7

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 8

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.

Question 9

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 10

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.

Question 11

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

Question 12

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

Question 13

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.

Question 14

Show the reaction catalyzed by glycogen synthase.

Accepted Answer

Glycogen synthase is an enzyme that play...

Question 15

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

Question 16

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.

Question 17

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

Accepted Answer

Glucose metabolism is a complex process ...

Question 18

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

Question 19

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

Question 20

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

Exam 15: Principles of Metabolic Regulation

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

Correct Answer
verified

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

Correct Answer
verified

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

Correct Answer
verified

Which pairing CORRECTLY matches an enzyme with its effector?

Correct Answer
verified

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

Correct Answer
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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?

Correct Answer
Answered by ExamLex AI
The bifunctional protein phosphofructoki...
View Answer

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?

Correct Answer
verified

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

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

Correct Answer
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Show the reaction catalyzed by glycogen synthase.

Correct Answer
Answered by ExamLex AI
Glycogen synthase is an enzyme that play...
View Answer

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

Correct Answer
verified

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

Correct Answer
verified

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.

Correct Answer
Answered by ExamLex AI
Glycogen synthase kinase-3 (GSK-3) inhib...
View Answer

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

Correct Answer
Answered by ExamLex AI
Glucose metabolism is a complex process ...
View Answer

Which substance activates glycogen synthase b in liver?

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

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
The question seems to be related to meta...
View Answer

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?

Correct Answer
verified

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

Correct Answer
verified

Exam 15: Principles of Metabolic Regulation

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Which pairing CORRECTLY matches an enzyme with its effector?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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?

Correct AnswerAnswered by ExamLex AIThe bifunctional protein phosphofructoki...View AnswerShow Answer

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?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Show the reaction catalyzed by glycogen synthase.

Correct AnswerAnswered by ExamLex AIGlycogen synthase is an enzyme that play...View AnswerShow Answer

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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.

Correct AnswerAnswered by ExamLex AIGlycogen synthase kinase-3 (GSK-3) inhib...View AnswerShow Answer

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

Correct AnswerAnswered by ExamLex AIGlucose metabolism is a complex process ...View AnswerShow Answer

Which substance activates glycogen synthase b in liver?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Correct AnswerAnswered by ExamLex AIThe question seems to be related to meta...View AnswerShow Answer

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?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
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Correct Answer
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Correct Answer
verified

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
The bifunctional protein phosphofructoki...
View Answer

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Correct Answer
verified

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
Glycogen synthase is an enzyme that play...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
Glycogen synthase kinase-3 (GSK-3) inhib...
View Answer

Correct Answer
Answered by ExamLex AI
Glucose metabolism is a complex process ...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
The question seems to be related to meta...
View Answer

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Correct Answer
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