Question
A 24-year-old woman with type 1 diabetes mellitus suddenly develops tremors, cold sweats, and confusion during an outdoor activity. She is only oriented to person and is unable to follow commands. Her friend administers an intramuscular injection with a substance that reverses her symptoms. Her fingerstick blood glucose concentration is 30 mg/dL. Which among the following is the most likely action of this drug:
| A. |
Activation of adenylyl cyclase
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| B. |
Inhibition of glycogen phosphorylase
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| C. |
Inhibition of the enzyme fructokinase
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| D. |
Activation of the enzyme glucokinase
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Show Answer
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Correct Answer � A
Explanation
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Ans. a. Activation of adenylyl cyclase
Nerve impulses and the binding of many hormones to cell surface receptors elicit changes in the rate of enzyme-catalyzed reactions within target cells by inducing the release or synthesis of specialized allosteric effectors called second messengers. The primary, or “first,” messenger is the hormone molecule or nerve impulse. Second messengers include 3′, 5′-cAMP, synthesized from ATP by the enzyme adenylyl cyclase in response to the hormone epinephrine, and Ca2+, which is stored inside the endoplasmic reticulum of most cells.Glucagon binds to the glucagon receptor that activates adenylyl cyclase to form cyclic AMP and shifts the hepatic cellular metabolism from glucose consumption and storage to glucose production. Therefore, glucagon reverses this patient’s insulin-induced hypoglycemia by stimulating gluconeogenesis and glycogenolysis to increase blood glucose concentration.
