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Chapter 22: Problem 4

Epinephrine A. mediates its effects by binding to cytoplasmic receptors. B. is synthesized in the adrenal cortex. C. is synthesized from norepinephrine by a methyl transferase (PNMT). D. Icads to the formation of \(c\) GMP. E. produces DAG and IP \(_{3}\)

Short Answer

Expert verified
A: Mediates its effects by binding to cytoplasmic receptors B: Is synthesized in the adrenal cortex C: Is synthesized from norepinephrine by a methyltransferase (PNMT) D: Leads to the formation of cGMP E: Produces DAG and IP\(_{3}\) Answer: C Explanation: Epinephrine is synthesized from norepinephrine by the enzyme phenylethanolamine N-methyltransferase (PNMT), which adds a methyl group to the amino group of norepinephrine. The other options are false because epinephrine binds to cell surface receptors called adrenergic receptors, is synthesized in the adrenal medulla, leads to the formation of cyclic AMP (cAMP), and does not produce DAG or IP\(_{3}\) in its signaling pathway.

Step by step solution

01

Option A: Mediates its effects by binding to cytoplasmic receptors

This option is false. Epinephrine mediates its effects by binding to cell surface receptors known as adrenergic receptors, not cytoplasmic receptors.
02

Option B: Is synthesized in the adrenal cortex

This option is false. Epinephrine is synthesized in the adrenal medulla, which is the inner part of the adrenal gland. The adrenal cortex synthesizes other hormones, such as corticosteroids.
03

Option C: Is synthesized from norepinephrine by a methyltransferase (PNMT)

This option is true. Epinephrine is synthesized from norepinephrine by the enzyme phenylethanolamine N-methyltransferase (PNMT), which adds a methyl group to the amino group of norepinephrine.
04

Option D: Leads to the formation of cGMP

This option is false. The binding of epinephrine to its receptors leads to the formation of cyclic AMP (cAMP), not cyclic GMP (cGMP).
05

Option E: Produces DAG and IP\(_{3}\)

This option is false. Epinephrine binding to its receptors leads to the activation of adenylate cyclase, which converts ATP to cAMP. DAG (diacylglycerol) and IP\(_{3}\) (inositol-1,4,5-trisphosphate) are produced by the phospholipase C (PLC) pathway, which is associated with other signaling pathways and receptors, not with the epinephrine signaling pathway. The correct answer is Option C: Epinephrine is synthesized from norepinephrine by a methyltransferase (PNMT).

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Most popular questions from this chapter

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