Metabolism of Glycogen Chapter

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What is the main function of liver glycogen?

To maintain the blood glucose concentration in the fasting state (correct)

To synthesize glycogen storage diseases

To provide a readily available source of glucose-1-phosphate for glycolysis within the muscle itself

To convert glucose-6-phosphatase into pyruvate

Where does glycogen occur mainly in the body?

Liver and muscle (correct)

Heart and lungs

Muscle and brain

Brain and liver

What is the approximate concentration of glycogen in the liver after a meal?

450 mmol /L glucose equivalents (correct)

100 mmol /L glucose equivalents

200 mmol /L glucose equivalents

550 mmol /L glucose equivalents

What is the fate of pyruvate formed by glycolysis in muscle?

It undergoes transamination to alanine Signup and view all the answers

What percentage of total body glycogen is in muscle?

About 75% Signup and view all the answers

What happens to liver glycogen after 12 to 18 hours of fasting?

It is almost totally depleted Signup and view all the answers

What is the result of phosphorylation of glycogen phosphorylase?

Increase in its activity Signup and view all the answers

What is the fate of cAMP in the presence of phosphodiesterase?

It is hydrolyzed Signup and view all the answers

What is the role of glycogen in the liver?

To provide free glucose for export to maintain the blood concentration of glucose Signup and view all the answers

What is the effect of insulin on phosphodiesterase in the liver?

It increases its activity Signup and view all the answers

What is the enzyme that catalyzes the phosphorylation of glycogen phosphorylase?

Phosphorylase kinase Signup and view all the answers

What is the source of glucose-6-phosphate for glycolysis in muscle?

Glycogen metabolism Signup and view all the answers

Where does glycogenin stay associated and form the core of?

A glycogen granule Signup and view all the answers

During glycogen elongation, what type of bond is formed between the glucose of UDPGlc and a terminal glucose residue of glycogen?

1,4-glycoside bond Signup and view all the answers

At what point does branching of glycogen occur?

When a growing chain is at least 11 glucose residues long Signup and view all the answers

What type of linkages are formed in the branching of glycogen?

1,4- and 1,6-glucosyl units Signup and view all the answers

What is the effect of insulin on cAMP levels?

Insulin decreases cAMP levels only after it has been raised by glucagon or epinephrine Signup and view all the answers

What is active in heart muscle but not in skeletal muscle?

Glucagon Signup and view all the answers

What is the allosteric activator of the dephosphorylated b-form of phosphorylase in muscle?

5' AMP Signup and view all the answers

What is the signal that triggers increased cAMP formation in the liver?

Glucagon Signup and view all the answers

What is the outcome of the reaction catalyzed by adenylate kinase?

2×ADP → ATP + 5' AMP Signup and view all the answers

Which of the following inhibits active phosphorylase A in the liver?

ATP and glucose-6-phosphate Signup and view all the answers

What is the response of the muscle cell to increasing ADP concentration?

Increased 5' AMP formation Signup and view all the answers

What is the outcome of phosphorylase kinase a phosphorylating phosphorylase b?

Phosphorylase a is formed Signup and view all the answers

What is the primary function of the sequence of reactions in glycogenolysis?

To amplify the hormonal signal at each step Signup and view all the answers

What triggers the initiation of both muscle contraction and glycogenolysis?

Increased cytosolic Ca2+ ion concentration Signup and view all the answers

What is the function of the δ subunit of muscle phosphorylase kinase?

To bind four Ca2+ Signup and view all the answers

In the liver, what is the response to stimulation of α1 adrenergic receptors by epinephrine and norepinephrine?

cAMP-independent activation of glycogenolysis Signup and view all the answers

What is the effect of phosphorylation on the γ subunit of muscle phosphorylase kinase?

It increases the enzyme's activity Signup and view all the answers

What is the role of Ca2+ in the activation of muscle phosphorylase?

It activates the enzyme's catalytic site Signup and view all the answers