Question 1

Why is the T state of glycogen phosphorylase less active?

Accepted Answer

A)  The adjacent amino acids are not phosphorylated, and thus the catalysis cannot be carried out. 
B)  The active site is partially blocked. 
C)  ATP cannot be bound by the T state. 
D)  Glucose-1-phosphate remains bound to the active site. 
E)  None of the answers is correct. 
A)  The adjacent amino acids are not phosphorylated, and thus the catalysis cannot be carried out. 
B)  The active site is partially blocked. 
C)  ATP cannot be bound by the T state. 
D)  Glucose-1-phosphate remains bound to the active site. 
E)  None of the answers is correct. B

Question 2

Why is the formation of glucose-1-phosphate energetically favorable even though the ΔG°′ is very small?

Accepted Answer

It is favored because the ratio of [P_i] to glucose-1-phosphate is greater than 100:1.

Question 3

What physiological conditions render phosphorylase b less active?

Accepted Answer

A)  High ATP, AMP, and glucose 6-phosphate levels 
B)  High ATP and low calcium ion levels 
C)  High ATP and glucose 6-phosphate levels 
D)  High AMP and low ATP levels 
E)  None of the answers is correct. 
A)  High ATP, AMP, and glucose 6-phosphate levels 
B)  High ATP and low calcium ion levels 
C)  High ATP and glucose 6-phosphate levels 
D)  High AMP and low ATP levels 
E)  None of the answers is correct. C

Question 4

Compare the evolutionary history of the catalytic and regulatory features of glycogen phosphorylase.

Accepted Answer

Comparison of the binding sites for gluc

Question 5

Give the reaction catalyzed by UDP-glucose pyrophosphorylase.

Accepted Answer

Glucose-1-

Question 6

What protein is the $\delta$ subunit of phosphorylase kinase?

Accepted Answer

A)  protein kinase A 
B)  phosphorylase 
C)  adenylate cyclase 
D)  protein phosphatase 1 
E)  calmodulin 
A)  protein kinase A 
B)  phosphorylase 
C)  adenylate cyclase 
D)  protein phosphatase 1 
E)  calmodulin

Question 7

What enzyme(s) is (are) required to cleave $\alpha$-1,6-glycosidic branches in glycogen?

Accepted Answer

A)  transferase 
B) $\alpha$-1,6-glucosidase 
C)  glycogen phosphatase 
D)  transferase and $\alpha$-1,6-glucosidase 
E)  $\alpha$-1,6-glucosidase and glycogen phosphatase 
A)  transferase 
B) $\alpha$-1,6-glucosidase 
C)  glycogen phosphatase 
D)  transferase and $\alpha$-1,6-glucosidase 
E)  $\alpha$-1,6-glucosidase and glycogen phosphatase

Question 8

What are the three steps in glycogen degradation?

Accepted Answer

The steps are 1) release of gl

Question 9

Which of the following occur after a carbohydrate-rich meal?

Accepted Answer

A)  Blood-glucose levels increase leading to glycogen storage in the liver. 
B)  Blood-glucose levels increase leading to glycogen storage in the muscle. 
C)  Glucose uptake from the blood increases as a result of the action of insulin. 
D)  Glucagon is absent. 
E)  All of the answers are correct. 
A)  Blood-glucose levels increase leading to glycogen storage in the liver. 
B)  Blood-glucose levels increase leading to glycogen storage in the muscle. 
C)  Glucose uptake from the blood increases as a result of the action of insulin. 
D)  Glucagon is absent. 
E)  All of the answers are correct.

Question 10

Insulin stimulates glycogen synthase by inactivating ________________________.

Accepted Answer

glycogen s

Question 11

What is the normal glucose concentration in blood?

Accepted Answer

A)  80-120 g/100 mL (4.4-6.7 M) 
B)  8-12 g/100 mL (0.44-0.67 M) 
C)  80-120 mg/100 mL (4.4-6.7 mM) 
D)  80-120 $\mu$g/100 mL (4.4-6.7 $\mu$M) 
E)  None of the answers is correct. 
A)  80-120 g/100 mL (4.4-6.7 M) 
B)  8-12 g/100 mL (0.44-0.67 M) 
C)  80-120 mg/100 mL (4.4-6.7 mM) 
D)  80-120 $\mu$g/100 mL (4.4-6.7 $\mu$M) 
E)  None of the answers is correct.

Question 12

In skeletal muscle, the binding of ___________ converts phosphorylase b into the active form.

Accepted Answer

The answer of In skeletal muscle, the binding of ___________...

Question 13

Critical hormones that signal for glycogen breakdown are

Accepted Answer

A)  insulin and epinephrine. 
B)  glucagon and epinephrine. 
C)  glucagon and insulin. 
D)  insulin, glucagon, and epinephrine. 
E)  None of the answers is correct. 
A)  insulin and epinephrine. 
B)  glucagon and epinephrine. 
C)  glucagon and insulin. 
D)  insulin, glucagon, and epinephrine. 
E)  None of the answers is correct.

Question 14

What hormone signifies the starved state?

Accepted Answer

A)  insulin 
B)  glucagon 
C)  epinephrine 
D)  cortisol 
E)  None of the answers is correct. 
A)  insulin 
B)  glucagon 
C)  epinephrine 
D)  cortisol 
E)  None of the answers is correct.

Question 15

Glycogen synthase catalyzes the transfer of a glucose residue from UDP-glucose to one of the _____________ ends of glycogen.

Accepted Answer

The answer of Glycogen synthase catalyzes the transfer of a...

Question 16

What type of glycosidic bond is found at the branch points of glycogen?

Accepted Answer

A)  $\alpha$-1,2 
B)  $\alpha$-1,4 
C)  $\alpha$-1,6 
D)  $\beta$-1,4 
E)  $\beta$-1,6 
A)  $\alpha$-1,2 
B)  $\alpha$-1,4 
C)  $\alpha$-1,6 
D)  $\beta$-1,4 
E)  $\beta$-1,6

Question 17

Which of the following serves as the glucose "sensor" enzyme in liver cells?

Accepted Answer

A)  glucose-6-phosphatase 
B)  hexokinase 
C)  phosphoglucomutase 
D)  UDP-glucose pyrophosphorylase 
E)  phosphorylase a 
A)  glucose-6-phosphatase 
B)  hexokinase 
C)  phosphoglucomutase 
D)  UDP-glucose pyrophosphorylase 
E)  phosphorylase a

Question 18

Thermodynamically, the reaction glucose-1-phosphate + UTP   UDP-glucose + PPi
is readily reversible. Explain why the formation of UDP-glucose from glucose-1-phosphate and UTP is essentially irreversible.

Accepted Answer

The hydrolysis of pyrophosphate (PP_i) to

Question 19

Phosphorylase kinase becomes fully active by being phosphorylated and binding ___________.

Accepted Answer

The answer of Phosphorylase kinase becomes fully active by being...

Question 20

How is phosphorylase b converted into phosphorylase a?

Accepted Answer

A)  Addition of a phosphate to a serine residue 
B)  Dimerization, which forms the active site pocket 
C)  Cleavage of 10 amino acids from the N-terminal end of the protein 
D)  Binding of glucose, an allosteric modifier 
E)  None of the answers is correct. 
A)  Addition of a phosphate to a serine residue 
B)  Dimerization, which forms the active site pocket 
C)  Cleavage of 10 amino acids from the N-terminal end of the protein 
D)  Binding of glucose, an allosteric modifier 
E)  None of the answers is correct.

Exam 21: Glycogen Metabolism

Why is the T state of glycogen phosphorylase less active?

Why is the formation of glucose-1-phosphate energetically favorable even though the ΔG°′ is very small?

What physiological conditions render phosphorylase b less active?

Compare the evolutionary history of the catalytic and regulatory features of glycogen phosphorylase.

Give the reaction catalyzed by UDP-glucose pyrophosphorylase.

What protein is the δ\deltaδ subunit of phosphorylase kinase?

What enzyme(s) is (are) required to cleave α\alphaα -1,6-glycosidic branches in glycogen?

What are the three steps in glycogen degradation?

Which of the following occur after a carbohydrate-rich meal?

Insulin stimulates glycogen synthase by inactivating ________________________.

What is the normal glucose concentration in blood?

In skeletal muscle, the binding of ___________ converts phosphorylase b into the active form.

Critical hormones that signal for glycogen breakdown are

What hormone signifies the starved state?

Glycogen synthase catalyzes the transfer of a glucose residue from UDP-glucose to one of the _____________ ends of glycogen.

What type of glycosidic bond is found at the branch points of glycogen?

Which of the following serves as the glucose "sensor" enzyme in liver cells?

Thermodynamically, the reaction glucose-1-phosphate + UTP UDP-glucose + PPi is readily reversible. Explain why the formation of UDP-glucose from glucose-1-phosphate and UTP is essentially irreversible.

Phosphorylase kinase becomes fully active by being phosphorylated and binding ___________.

How is phosphorylase b converted into phosphorylase a?

Biochemistry: an Evolving Science

Protein Composition and Structure

Exploring Proteins and Proteomes

DNA, RNA, and the Flow of Genetic Information

Exploring Genes and Genomes

Exploring Evolution and Bioinformatics

Hemoglobin: a Portrait of a Protein in Action

Enzymes: Basic Concepts and Kinetics

Oxidative Phosphorylation

Catalytic Strategies

Regulatory Strategies

Carbohydrates

Lipids and Cell Membranes

Membrane Channels and Pumps

Signal-Transduction Pathways

Metabolism: Basic Concepts and Design

Glycolysis and Gluconeogenesis

The Citric Acid Cycle

The Light Reactions of Photosynthesis

The Calvin Cycle and the Pentose Phosphate Pathway

Fatty Acid Metabolism

Protein Turnover and Amino Acid Catabolism

The Biosynthesis of Amino Acids

Nucleotide Biosynthesis

Biosynthesis of Membrane Lipids and Steroids

The Integration of Metabolism

DNA Replication, Repair, and Recombination

Rna Synthesis and Processing

Protein Synthesis

The Control of Gene Expression in Prokaryotes

The Control of Gene Expression in Eukaryotes

Sensory Systems

The Immune System

Molecular Motors

Drug Development

Filters

What protein is the $\delta$ subunit of phosphorylase kinase?

What enzyme(s) is (are) required to cleave $\alpha$ -1,6-glycosidic branches in glycogen?

Thermodynamically, the reaction glucose-1-phosphate + UTP UDP-glucose + PP_i is readily reversible. Explain why the formation of UDP-glucose from glucose-1-phosphate and UTP is essentially irreversible.