30 Questions
Which enzyme catalyzes the conversion of glucose to Glucose-6-Phosphate in muscle?
Hexokinase
What is the main function of UDPGlc pyrophosphorylase?
Catalyzing glycogen synthesis
Which organ mainly utilizes glucokinase for the conversion of glucose to Glucose-6-Phosphate?
Liver
What is the immediate precursor of UDPGlc in glycogenesis?
Glucose-1-Phosphate
Which process involves the transfer of a phosphate group from the sixth carbon to the first carbon of the glucose molecule?
Isomerization to Glucose-1-Phosphate
What is the final product formed by the catalytic action of UDPGlc pyrophosphorylase?
Uridine diphosphate glucose (UDPGlc)
What is the main enzyme that catalyzes the rate-limiting step in glycogenolysis?
Glycogen phosphorylase
What is the purpose of the debranching enzyme in glycogenolysis?
To transfer a trisaccharide unit from one branch to another, exposing the 1,6 branch point
What is the role of phosphoglucomutase in glycogenolysis?
It catalyzes the conversion of glucose 1-phosphate to glucose-6-phosphate, and the reverse reaction is also possible
Which of the following statements about the differences between glycogenolysis and glycogenesis is correct?
Glycogenolysis and glycogenesis are separate pathways that use different sets of enzymes
What is the role of glucose-6-phosphatase in glycogenolysis in the liver?
It catalyzes the hydrolysis of glucose-6-phosphate to yield free glucose, which is then exported to increase blood glucose concentration
What is the final outcome of the combined action of phosphorylase and the other enzymes involved in glycogenolysis?
The complete breakdown of glycogen to yield free glucose
What is the role of 5' AMP in muscle phosphorylase?
It activates the inactive form (phosphorylase b) of the enzyme
What is the primary signal that leads to increased cAMP formation in liver cells?
Glucagon secretion
Which of the following is an allosteric inhibitor of active phosphorylase A in both liver and muscle tissues?
ATP
What is the role of cAMP in the activation of glycogen phosphorylase?
It activates phosphorylase kinase a, which then activates phosphorylase b
What is the primary signal that leads to increased cAMP formation in muscle cells?
Norepinephrine secretion
Which of the following is an allosteric inhibitor of active phosphorylase A in liver, but not in muscle?
Free glucose
What enzyme catalyzes the formation of a glycoside bond between C-1 of the glucose of UDPGlc and C-4 of a terminal glucose residue of glycogen?
Glycogen synthase
At which end of the glycogen molecule does the addition of a glucose residue to a preexisting glycogen chain occur?
Nonreducing, outer end
What is the minimum length of a growing glycogen chain before the branching enzyme can transfer a part of the 1 4-chain to a neighboring chain to form a 1 6 linkage?
11 glucose residues
What is the role of insulin in the regulation of glycogen metabolism?
Insulin decreases the level of cAMP only after it has been raised by glucagon or epinephrine
Which hormone is active in heart muscle but not in skeletal muscle?
Glucagon
What is the relationship between the enzymes glucan transferase and debranching enzyme?
Glucan transferase and debranching enzyme appear to be two separate activities of the same enzyme
How is phosphorylase A inactivated?
By protein phosphatase-1
What inhibits protein phosphatase-1?
Inhibitor-1 phosphorylated by cAMP-dependent protein kinase
How does insulin reinforce the inactivation of phosphorylase b?
By increasing glucose uptake
What happens to glycogen synthase a to make it active?
It gets dephosphorylated
How many different protein kinases act on glycogen synthase?
Six
What type of hormonal action allows the inhibition of glycogen synthesis along with the activation of glycogenolysis?
cAMP-mediated hormonal action
Learn about glycogen storage diseases, conditions caused by deficient mobilization or abnormal deposition of glycogen, leading to liver damage and muscle weakness. Explore the process of glycogenesis, involving UDP-Glucose and the conversion of glucose to Glucose-6-Phosphate (G6P) in muscle and liver.
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