29 Questions
Which factor deactivates liver phosphorylase enzyme?
Glucose
What effect do hormones that increase cAMP levels have on the activation of glycogen phosphorylase?
Promote activation
How does insulin affect the activity of phosphoprotein phosphatase in relation to phosphorylase?
Promotes activation
Under what conditions does glucagon stimulate liver glycogen breakdown?
Low blood glucose
Which hormone enhances glycogen breakdown in both muscle and liver for muscle contraction?
Epinephrine
Which process dominates in the liver during fasting?
Glycogenolysis
What is the effect of high concentrations of ATP on muscle phosphorylase activity?
Allosteric inhibition
Which hormone activates phosphorylase a in skeletal muscle?
Epinephrine
What is the primary function of muscle phosphorylase in its 'a' form?
Catalytically active
Which compound is converted to glucose 6-phosphate in skeletal muscle?
Glucose 1-phosphate
In skeletal muscle, what regulates glycogen degradation in response to ATP needs?
ATP and AMP levels
Which molecule activates glycogen phosphorylase in the glucagon/epinephrine signaling pathway?
cAMP
In resting muscle, which form is predominantly inactive?
b form
What is the end product generated by glucose-6-phosphate entering the glycolytic pathway?
ATP
Which molecule acts as a feedback inhibitor of glycogen phosphorylase?
ATP
What provides a direct and rapid means of stimulating glycogen degradation during muscle contraction?
Ca released from sarcoplasmic reticulum
Glycogen phosphorylase generates which molecule that is isomerized into glucose-6-phosphate?
Glucose-1-phosphate
How does insulin stimulate glycogen synthesis?
By inactivating GSK-3 and activating glycogen synthase
What is the role of Protein Phosphatase 1 (PP1) in glycogen metabolism?
Removes phosphoryl groups from glycogen synthase b
How do myocytes contribute to lowering blood glucose in response to insulin?
By moving GLUT4 to the plasma membrane for increased glucose uptake
What effect does elevated insulin have on glycogen synthesis in myocytes?
Activates PP1 and inactivates GSK3
What is the consequence of removing phosphoryl groups from glycogen synthase b by PP1?
Conversion to the active glycogen synthase a form
How are cAMP cascades involved in regulating glycogen metabolism?
They shut off glycogen synthesis
What effect does glucagon have on muscle glycogen levels?
Has no effect on muscle glycogen levels
What is the role of AMP in muscle glycogen phosphorylase activation?
Serves as an allosteric activator of muscle glycogen phosphorylase
From where do the effects of Ca in muscle primarily result?
Release of Ca from the sarcoplasmic reticulum after neural stimulation
How does epinephrine-stimulated phosphorylation affect skeletal muscle glycogen?
Induces similar effects as in liver glycogen metabolism
What role does covalent modification play in the regulation of glycogen synthase?
Converts active form into inactive form
How is glycogen synthase regulated by ATP and glucose-6-P?
Stimulated by ATP and glucose-6-P
Test your knowledge on liver phosphorylase, glucose production, and the regulation of enzyme activity by hormones such as glucagon, epinephrine, and insulin.
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