Question 1

Mutating which proteins is unlikely to result in a glycogen storage disease?

Accepted Answer

A)  pyruvate carboxylase 
B)  GLUT2 
C)  phosphorylase 
D)  PFK-1 in muscle 
E)  phosphorylase kinase 
A)  pyruvate carboxylase 
B)  GLUT2 
C)  phosphorylase 
D)  PFK-1 in muscle 
E)  phosphorylase kinase

Question 2

Order the steps leading to glycogen synthesis resulting from the stimulation of liver cells by glucose.
1) Xyulose-5-phosphate is formed
2) Glucose is phosphorylated to glucose-6-phosphate
3) Glycogen synthase is dephosphorylated
4) Protein phosphatase 2A is activated

Accepted Answer

The steps leading to glycogen synthesis

Question 3

Which tissue has the FASTEST average rate of protein turnover?

Accepted Answer

A)  the heart 
B)  the brain 
C)  the kidneys 
D)  skeletal muscle 
E)  the liver 
A)  the heart 
B)  the brain 
C)  the kidneys 
D)  skeletal muscle 
E)  the liver

Question 4

Briefly explain the differences between the flux control, elasticity, and response coefficients.

Accepted Answer

Flux control coefficients measure the se

Question 5

Which statement about mammalian glycogen synthase is NOT correct?

Accepted Answer

A)  It is especially predominant in liver and muscle. 
B)  The donor molecule is a sugar nucleotide. 
C)  The phosphorylated form of this enzyme is inactive. 
D)  This enzyme adds glucose units to the nonreducing end of glycogen branches. 
E)  This enzyme adds the initial glucose unit to a tyrosine residue in glycogenin. 
A)  It is especially predominant in liver and muscle. 
B)  The donor molecule is a sugar nucleotide. 
C)  The phosphorylated form of this enzyme is inactive. 
D)  This enzyme adds glucose units to the nonreducing end of glycogen branches. 
E)  This enzyme adds the initial glucose unit to a tyrosine residue in glycogenin.

Question 6

Is glycogen phosphorylase activated, inhibited, or unaffected in response to a glucagon signal in liver tissue?

Accepted Answer

A)  activated 
B)  inhibited 
C)  unaffected 
A)  activated 
B)  inhibited 
C)  unaffected

Question 7

How are the opposing pathways of glycolysis and gluconeogenesis prevented from extensive futile cycling?

Accepted Answer

A)  At least seven of the enzymes in the two pathways are different. 
B)  Key enzymes are regulated in a coordinated and reciprocal manner. 
C)  Catabolic and anabolic pathways do not take place in the same cellular compartments. 
D)  The overall free-energy change always favors the catabolic pathway. 
E)  Gluconeogenesis involves three endergonic bypass reactions. 
A)  At least seven of the enzymes in the two pathways are different. 
B)  Key enzymes are regulated in a coordinated and reciprocal manner. 
C)  Catabolic and anabolic pathways do not take place in the same cellular compartments. 
D)  The overall free-energy change always favors the catabolic pathway. 
E)  Gluconeogenesis involves three endergonic bypass reactions.

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. 
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 9

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 10

Which factor is an example of flux regulation, not flux control, upon an increase in blood glucose levels?

Accepted Answer

A)  induction of insulin 
B)  increased glucose transport into cells 
C)  induction of the synthesis of hexokinase 
D)  induction of the synthesis of phosphofructokinase-1 
E)  activation of glycogen synthase 
A)  induction of insulin 
B)  increased glucose transport into cells 
C)  induction of the synthesis of hexokinase 
D)  induction of the synthesis of phosphofructokinase-1 
E)  activation of glycogen synthase

Question 11

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

Accepted Answer

The biological advantage of synthesizing

Question 12

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

Accepted Answer

Metabolic regulation and metabolic contr

Question 13

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 14

Although most of the glycogen stored in a human body is found in skeletal muscle, this tissue does not play a role in maintaining blood sugar levels between meals. How are myocytes precluded from doing so?

Accepted Answer

Myocytes, or muscle cells, store glycoge

Question 15

After a meal rich in carbohydrates, which change would NOT be expected in a normal human?

Accepted Answer

A)  increased secretion of the pancreatic hormone, insulin 
B)  increased activity of the liver enzyme, glucokinase 
C)  increased glucose uptake in myocytes via GLUT4 transporters 
D)  decreased activity of GSK-3 in both myocytes and hepatocytes 
E)  increased activity of glucose 6-phosphatase in hepatocytes 
A)  increased secretion of the pancreatic hormone, insulin 
B)  increased activity of the liver enzyme, glucokinase 
C)  increased glucose uptake in myocytes via GLUT4 transporters 
D)  decreased activity of GSK-3 in both myocytes and hepatocytes 
E)  increased activity of glucose 6-phosphatase in hepatocytes

Question 16

Which statement is TRUE of muscle glycogen phosphorylase?

Accepted Answer

A)  It catalyzes phosphorolysis of the ($\alpha$1 $\rightarrow$ 6) bonds at the branch points of glycogen. 
B)  It catalyzes the degradation of glycogen by hydrolysis of glycosidic bonds. 
C)  It degrades glycogen to form glucose 6-phosphate. 
D)  It exists in an active (a) form and an inactive (b) form that is allosterically regulated by AMP. 
E)  It removes glucose residues from the reducing ends of the glycogen chains. 
A)  It catalyzes phosphorolysis of the ($\alpha$1 $\rightarrow$ 6) bonds at the branch points of glycogen. 
B)  It catalyzes the degradation of glycogen by hydrolysis of glycosidic bonds. 
C)  It degrades glycogen to form glucose 6-phosphate. 
D)  It exists in an active (a) form and an inactive (b) form that is allosterically regulated by AMP. 
E)  It removes glucose residues from the reducing ends of the glycogen chains.

Question 17

Explain the difference between homeostasis and equilibrium.

Accepted Answer

Homeostasis and equilibrium are two rela

Question 18

Why is it important for proper cell function that proteins turn over rather than persisting indefinitely after being synthesized?

Accepted Answer

Protein turnover, the continuous process

Question 19

Write out the reaction catalyzed by adenylate kinase and explain why this reaction is so important in skeletal muscle.

Accepted Answer

Adenylate kinase catalyzes the reaction:

Question 20

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 and glycogen breakdow

Exam 15: Principles of Metabolic Regulation

Mutating which proteins is unlikely to result in a glycogen storage disease?

Order the steps leading to glycogen synthesis resulting from the stimulation of liver cells by glucose. 1) Xyulose-5-phosphate is formed 2) Glucose is phosphorylated to glucose-6-phosphate 3) Glycogen synthase is dephosphorylated 4) Protein phosphatase 2A is activated

Which tissue has the FASTEST average rate of protein turnover?

Briefly explain the differences between the flux control, elasticity, and response coefficients.

Which statement about mammalian glycogen synthase is NOT correct?

Is glycogen phosphorylase activated, inhibited, or unaffected in response to a glucagon signal in liver tissue?

How are the opposing pathways of glycolysis and gluconeogenesis prevented from extensive futile cycling?

Glycogenin:

The MOST sensitive indicator of the energetic status of the cell is the concentration of:

Which factor is an example of flux regulation, not flux control, upon an increase in blood glucose levels?

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

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

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

Although most of the glycogen stored in a human body is found in skeletal muscle, this tissue does not play a role in maintaining blood sugar levels between meals. How are myocytes precluded from doing so?

After a meal rich in carbohydrates, which change would NOT be expected in a normal human?

Which statement is TRUE of muscle glycogen phosphorylase?

Explain the difference between homeostasis and equilibrium.

Why is it important for proper cell function that proteins turn over rather than persisting indefinitely after being synthesized?

Write out the reaction catalyzed by adenylate kinase and explain why this reaction is so important in skeletal muscle.

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

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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