Question 1

Which of the following does not contribute to the regulation of enzymatic activity?

Accepted Answer

A)  Protein phosphorylation
B)  Allosteric regulation
C)  Protein stability
D)  mRNA stability
E)  DNA stabilityF) All of the above
G) B) and E)

Question 2

The most sensitive indicator of the energetic status of the cell is the concentration of

Accepted Answer

A)  AMP.
B)  ADP.
C)  ATP.
D)  cAMP.
E)  glucose.F) B) and E)
G) C) and D)

Question 3

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 A and C.
E)  both B and C.F) A) and B)
G) D) and E)

Question 4

Glycogen synthesis and glycogen breakdown are catalyzed by separate enzymes.Contrast the reactions in terms of substrate,cofactors (if any),and regulation.

Accepted Answer

Glycogen synthesis is catalyzed by glyco...

Question 5

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

Accepted Answer

Glucose is taken up by the cell and converted to xyulose-5-phosphate,which in turn activates protein phosphatase 2A (PP2A).PP2A dephosphorylates carbohydrate response element binding protein (ChREBP)in the cyotosol.ChREBP is then taken up into the nucleus where it is further dephosphorylated by PP2A.ChREBP then forms a complex with Mlx to up-regulate the transcription of the gene encoding pyruvate kinase.

Question 6

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.F) B) and C)
G) B) and D)

Question 7

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

Accepted Answer

A)  the concentration of the enzyme itself.
B)  the concentration of other enzymes in the pathway.
C)  the levels of regulatory molecules.
D)  the amounts of substrate molecules present at each step.
E)  All of the aboveF) A) and E)
G) None of the above E

Question 8

Glycogenin:

Accepted Answer

A)  catalyzes the conversion of starch into glycogen.
B)  is the enzyme responsible for forming branches in glycogen.
C)  is the gene that encodes glycogen synthase.
D)  is the primer on which new glycogen chains are initiated.
E)  regulates the synthesis of glycogen.F) A) and B)
G) All of the above

Question 9

The glycogen-branching enzyme catalyzes:

Accepted Answer

A)  degradation of ( α\alphaα 1 →\rightarrow→  4) linkages in glycogen
B)  formation of ( α\alphaα 1  →\rightarrow→  4) linkages in glycogen.
C)  formation of ( α\alphaα 1  →\rightarrow→  6) linkages during glycogen synthesis.
D)  glycogen degradation in tree branches.
E)  removal of unneeded glucose residues at the ends of branches. F) D) and E)
G) C) and D) C

Question 10

Explain the distinction between metabolic "regulation" and metabolic "control" in a multienzyme pathway.

Accepted Answer

Regulation refers to rebalanci...

Question 11

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

Normally,[ATP] is 5-10 mM,while [AMP] is...

Question 12

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

Glucagon,signaling low blood sugar,stimu...

Question 13

The enzyme glycogen phosphorylase:

Accepted Answer

A)  catalyzes a cleavage of  β\betaβ (1  →\rightarrow→  4) bonds.
B)  catalyzes a hydrolytic cleavage of  α\alphaα (1  →\rightarrow→  4) bonds.
C)  is a substrate for a kinase.
D)  uses glucose 6-phosphate as a substrate.
E)  uses glucose as a substrate. F) A) and C)
G) A) and B)

Question 14

What is the biological advantage of synthesizing glycogen with many branches?

Accepted Answer

Highly branched glycogen is more soluble...

Question 15

Which of the following 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.F) B) and C)
G) B) and E)

Question 16

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.F) A) and D)
G) D) and E)

Question 17

Glycogen phosphorylase a can be inhibited at an allosteric site by:

Accepted Answer

A)  AMP.
B)  calcium.
C)  GDP.
D)  glucagon.
E)  glucose.F) B) and C)
G) A) and D)

Question 18

Which one of the following types of mechanisms 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 subunitsF) C) and D)
G) A) and D)

Question 19

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

Up-regulated examples: phospho...

Question 20

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

Accepted Answer

A)  the reaction will be at equilibrium.
B)  the reaction will go backward and be endergonic.
C)  the reaction will go backward and be exergonic.
D)  the reaction will go forward and be endergonic.
E)  the reaction will go forward and be exergonic.F) D) and E)
G) All of the above

Exam 15: Principles of Metabolic Regulation

Which of the following does not contribute to the regulation of enzymatic activity?

Correct Answer
verified

The most sensitive indicator of the energetic status of the cell is the concentration of

Correct Answer
verified

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

Correct Answer
verified

Glycogen synthesis and glycogen breakdown are catalyzed by separate enzymes.Contrast the reactions in terms of substrate,cofactors (if any),and regulation.

Correct Answer
verified
Glycogen synthesis is catalyzed by glyco...
View Answer

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

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

Correct Answer
verified

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

Correct Answer
verified
E

Glycogenin:

Correct Answer
verified

The glycogen-branching enzyme catalyzes:

Correct Answer
verified
C

Explain the distinction between metabolic "regulation" and metabolic "control" in a multienzyme pathway.

Correct Answer
verified
Regulation refers to rebalanci...
View Answer

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?

Correct Answer
verified
Normally,[ATP] is 5-10 mM,while [AMP] is...
View 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 Answer
verified
Glucagon,signaling low blood sugar,stimu...
View Answer

The enzyme glycogen phosphorylase:

Correct Answer
verified

What is the biological advantage of synthesizing glycogen with many branches?

Correct Answer
verified
Highly branched glycogen is more soluble...
View Answer

Which of the following is true of glycogen synthesis and breakdown?

Correct Answer
verified

Cellular isozymes of pyruvate kinase are allosterically inhibited by:

Correct Answer
verified

Glycogen phosphorylase a can be inhibited at an allosteric site by:

Correct Answer
verified

Which one of the following types of mechanisms is not known to play a role in the reversible alteration of enzyme activity?

Correct Answer
verified

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.

Correct Answer
verified
Up-regulated examples: phospho...
View Answer

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

Correct Answer
verified

Exam 15: Principles of Metabolic Regulation

Which of the following does not contribute to the regulation of enzymatic activity?

Correct AnswerverifiedShow Answer

The most sensitive indicator of the energetic status of the cell is the concentration of

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Glycogen synthesis and glycogen breakdown are catalyzed by separate enzymes.Contrast the reactions in terms of substrate,cofactors (if any),and regulation.

Correct AnswerverifiedGlycogen synthesis is catalyzed by glyco...View AnswerShow Answer

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

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedE

Glycogenin:

Correct AnswerverifiedShow Answer

The glycogen-branching enzyme catalyzes:

Correct AnswerverifiedC

Explain the distinction between metabolic "regulation" and metabolic "control" in a multienzyme pathway.

Correct AnswerverifiedRegulation refers to rebalanci...View AnswerShow Answer

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?

Correct AnswerverifiedNormally,[ATP] is 5-10 mM,while [AMP] is...View AnswerShow 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 AnswerverifiedGlucagon,signaling low blood sugar,stimu...View AnswerShow Answer

The enzyme glycogen phosphorylase:

Correct AnswerverifiedShow Answer

What is the biological advantage of synthesizing glycogen with many branches?

Correct AnswerverifiedHighly branched glycogen is more soluble...View AnswerShow Answer

Which of the following is true of glycogen synthesis and breakdown?

Correct AnswerverifiedShow Answer

Cellular isozymes of pyruvate kinase are allosterically inhibited by:

Correct AnswerverifiedShow Answer

Glycogen phosphorylase a can be inhibited at an allosteric site by:

Correct AnswerverifiedShow Answer

Which one of the following types of mechanisms is not known to play a role in the reversible alteration of enzyme activity?

Correct AnswerverifiedShow Answer

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.

Correct AnswerverifiedUp-regulated examples: phospho...View AnswerShow Answer

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

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
Glycogen synthesis is catalyzed by glyco...
View Answer

Correct Answer
verified

Correct Answer
verified
E

Correct Answer
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Correct Answer
verified
C

Correct Answer
verified
Regulation refers to rebalanci...
View Answer

Correct Answer
verified
Normally,[ATP] is 5-10 mM,while [AMP] is...
View Answer

Correct Answer
verified
Glucagon,signaling low blood sugar,stimu...
View Answer

Correct Answer
verified

Correct Answer
verified
Highly branched glycogen is more soluble...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
Up-regulated examples: phospho...
View Answer

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

Correct Answer
verified