30 Questions
What is the main function of liver glycogen?
To maintain the blood glucose concentration in the fasting state
Where does glycogen occur mainly in the body?
Liver and muscle
What is the approximate concentration of glycogen in the liver after a meal?
450 mmol /L glucose equivalents
What is the fate of pyruvate formed by glycolysis in muscle?
It undergoes transamination to alanine
What percentage of total body glycogen is in muscle?
About 75%
What happens to liver glycogen after 12 to 18 hours of fasting?
It is almost totally depleted
What is the result of phosphorylation of glycogen phosphorylase?
Increase in its activity
What is the fate of cAMP in the presence of phosphodiesterase?
It is hydrolyzed
What is the role of glycogen in the liver?
To provide free glucose for export to maintain the blood concentration of glucose
What is the effect of insulin on phosphodiesterase in the liver?
It increases its activity
What is the enzyme that catalyzes the phosphorylation of glycogen phosphorylase?
Phosphorylase kinase
What is the source of glucose-6-phosphate for glycolysis in muscle?
Glycogen metabolism
Where does glycogenin stay associated and form the core of?
A glycogen granule
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
At what point does branching of glycogen occur?
When a growing chain is at least 11 glucose residues long
What type of linkages are formed in the branching of glycogen?
1,4- and 1,6-glucosyl units
What is the effect of insulin on cAMP levels?
Insulin decreases cAMP levels only after it has been raised by glucagon or epinephrine
What is active in heart muscle but not in skeletal muscle?
Glucagon
What is the allosteric activator of the dephosphorylated b-form of phosphorylase in muscle?
5' AMP
What is the signal that triggers increased cAMP formation in the liver?
Glucagon
What is the outcome of the reaction catalyzed by adenylate kinase?
2×ADP → ATP + 5' AMP
Which of the following inhibits active phosphorylase A in the liver?
ATP and glucose-6-phosphate
What is the response of the muscle cell to increasing ADP concentration?
Increased 5' AMP formation
What is the outcome of phosphorylase kinase a phosphorylating phosphorylase b?
Phosphorylase a is formed
What is the primary function of the sequence of reactions in glycogenolysis?
To amplify the hormonal signal at each step
What triggers the initiation of both muscle contraction and glycogenolysis?
Increased cytosolic Ca2+ ion concentration
What is the function of the δ subunit of muscle phosphorylase kinase?
To bind four Ca2+
In the liver, what is the response to stimulation of α1 adrenergic receptors by epinephrine and norepinephrine?
cAMP-independent activation of glycogenolysis
What is the effect of phosphorylation on the γ subunit of muscle phosphorylase kinase?
It increases the enzyme's activity
What is the role of Ca2+ in the activation of muscle phosphorylase?
It activates the enzyme's catalytic site
Test your understanding of glycogen, the major storage carbohydrate in animals, and its importance as a reserve. Learn about the synthesis and breakdown of glycogen, its regulation, and glycogen storage diseases. Assess your knowledge of this crucial biological process.
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