This set of Molecular Endocrinology Multiple Choice Questions & Answers (MCQs) focuses on “Metabolic Role of Catecholamines”.
1. What is the role of epinephrine in glycogen synthesis in the hepatic tissues?
a) Enhances glycogenolysis
b) Enhances glycogenesis
c) Enhances glycolysis
d) Inhibits glycogenolysis
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Explanation: Epinephrine causes accelerated liver glycogen degradation (glycogenolysis), which induces hyperglycemia. Its action is mediated by two ways, one by binding to beta-2 receptor and the other by binding to alpha-1 receptor.
2. What is the role of epinephrine in heart glycogen metabolism?
a) Reduces heart glycogen
b) Increases heart glycogen
c) Inactivates heart glycogen
d) Induces glycogenolysis
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Explanation: In vivo, an improvement in heart glycogen will result from the action of epinephrine. This is mostly secondary to the hormone effect that induces adipolysis and elevated FFA on adipose tissue. Unlike the liver and skeletal muscle, with fasting, the heart muscle enhances its glycogen content. Insulin, through the simultaneous stimulation of glucose transport and glycogen synthase activity, also raises glycogen reserves.
3. What is the reason for increased glycogen in the heart muscles?
a) Glycolysis
b) Glycogenolysis
c) Gluconeogenesis
d) TCA cycle
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Explanation: In the heart muscles, fatty acids are used as fuel. Gluconeogenesis is responsible for increased glycogen, glucose is not used for energy, and it is redirected to glycogen production. Gluconeogenesis is stimulated by the diabetogenic hormones (glucagon, growth hormone, epinephrine, and cortisol).
4. The effect of rising cyclic AMP in liver cells is close to that of glucagon.
a) True
b) False
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Explanation: The effect of an increase in hepatic cell cyclic AMP is similar to glucagon. However, epinephrine and/or glucagon cyclic AMP measurements suggest that glucagon is by far the most active hormone in liver tissue.
5. Glucagon is the most active hormone in muscle tissues.
a) True
b) False
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Explanation: Epinephrine in muscle tissue induces glycogen breakdown (glycogenolysis) by increasing the amount of cyclic AMP (β-effect), but it is more active than glucagon in this tissue. Due to the absence of unique receptors, glucagon has either little effect or no effect.
6. What is the role of epinephrine in lipid metabolism?
a) Induces lipogenesis
b) Induces lipolysis
c) Reduces lipolysis
d) Inhibits lipogenesis
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Explanation: By increasing the cyclic-AMP level (β1 effect), both epinephrine and norepinephrine improve TG breakdown in adipose tissue. The net result of lipolysis is that FFA and glycerol are quickly released into the blood from adipose tissue.
7. What is the role of epinephrine in maintaining the blood lactic acid levels?
a) Increases
b) Catabolism
c) Maintains
d) Decreases
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Explanation: By facilitating muscle glycolysis, epinephrine raises the blood LA level. Norepinephrine has relatively little effect on lactic acid in the blood. Epinephrine induces the release of lactate from the skeletal muscle by activating Na+, K+-ATPase or gluconeogenesis for oxidation purposes (Cori cycle).
8. What is the role of epinephrine in the insulin release?
a) Induces
b) Insulin anabolism
c) Insulin catabolism
d) Inhibits
View Answer
Explanation: Epinephrine has direct inhibitory effect on the release of insulin from β-cells of pancreas (alpha-2 effect). Here, the alpha-adrenergic reaction to epinephrine prevails in the pancreas and cyclic AMP reduces which in turn leads to the blockage of insulin release.
9. Which among the following is the alpha blocker of epinephrine?
a) Phentolamine
b) Zintec
c) cAMP
d) cGMP
View Answer
Explanation: The β-effect predominates in the presence of an alpha-blocker, such as “phentolamine” (Regitine). As a result, cyclic AMP and insulin secretion are triggered by epinephrine. Phentolamine is a synthetic imidazoline with the activity of an alpha-adrenergic antagonist.
10. What is the role of thyroid hormones in the calorigenic action of catecholamines?
a) Blocks the action
b) Induces the action
c) Reduces the action
d) No or little effect
View Answer
Explanation: The calorigenic activity of Norepinephrine and epinephrine is almost equally effective. Thyroid hormones are very essential for the catecholamines in order to carry out their calorigenic action. In the absence of the thyroid and adrenal cortex, the calorigenic effect cannot be implemented which suggests that thyroid hormones are that much essential in the calorigenic action of catecholamines.
Sanfoundry Global Education & Learning Series – Molecular Endocrinology.
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