Question 1

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 2

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 above 
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 above E

Question 3

The glycogen-branching enzyme catalyzes:

Accepted Answer

A) degradation of ($\alpha$1$\rightarrow$ 4)linkages in glycogen 
B) formation of ($\alpha$1 $\rightarrow$ 4)linkages in glycogen. 
C) formation of ($\alpha$1 $\rightarrow$ 6)linkages during glycogen synthesis. 
D) glycogen degradation in tree branches. 
E) removal of unneeded glucose residues at the ends of branches. 
A) degradation of ($\alpha$1$\rightarrow$ 4)linkages in glycogen 
B) formation of ($\alpha$1 $\rightarrow$ 4)linkages in glycogen. 
C) formation of ($\alpha$1 $\rightarrow$ 6)linkages during glycogen synthesis. 
D) glycogen degradation in tree branches. 
E) removal of unneeded glucose residues at the ends of branches. C

Question 4

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 5

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. 
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.

Question 6

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

Question 7

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 8

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 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

Glucagon,signaling low blood sugar,stimu

Question 10

The enzyme glycogen phosphorylase:

Accepted Answer

A) catalyzes a cleavage of $\beta$(1 $\rightarrow$ 4)bonds. 
B) catalyzes a hydrolytic cleavage of $\alpha$(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. 
A) catalyzes a cleavage of $\beta$(1 $\rightarrow$ 4)bonds. 
B) catalyzes a hydrolytic cleavage of $\alpha$(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.

Question 11

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

Accepted Answer

Highly branched glycogen is more soluble

Question 12

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 13

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 14

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 stability 
A) Protein phosphorylation 
B) Allosteric regulation 
C) Protein stability 
D) mRNA stability 
E) DNA stability

Question 15

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

Accepted Answer

Regulation refers to rebalanci

Question 16

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. 
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.

Question 17

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 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 18

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. 
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.

Question 19

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

Accepted Answer

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

Question 20

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. 
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.

Exam 15: Principles of Metabolic Regulation

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

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

The glycogen-branching enzyme catalyzes:

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?

Glycogenin:

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

Cellular isozymes of pyruvate kinase are allosterically inhibited by:

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

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?

The enzyme glycogen phosphorylase:

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

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.

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

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

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

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

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

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

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

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

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

Recombinant Dna Technology

Lipids

Biological Membranes and Transport

Biosignaling

Principles of Bioenergetics

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

Integration and Hormonal Regulation of Mammalian Metabolism

Genes and Chromosomes

Dna Metabolism

Rna Metabolism

Protein Metabolism

Regulation of Gene Expression

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