The figure (Figure 2) below shows the pathway through which nitric oxide (NO) tr

Question

The figure (Figure 2) below shows the pathway through which nitric oxide (NO) triggers smooth muscle relaxation in a blood-vessel wall. Which of the following situations would lead to relaxation of the smooth muscle cells in the absence of acetylcholine? Explain your answer. a) A smooth muscle cell that has a defect in guanylyl cyclase such that it cannot bind NO. b) A muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP. c) A muscle cell that has cyclic GMP phosphodiesterase constitutively active. d) A drug that blocks an enzyme involved in the metabolic pathway from arginine to NO.

Explanation / Answer

Answer

Option b is the right answer because defected guanylyl cyclase will constitutively convert the GTP to cyclic GMP which will continuously relax the smooth muscles irrespective of presence or absence of acetylcholine. The goal of a function of acetylcholine is to produce NO which in turn activate the guanylyl cyclase to produce the cGMP which relaxes smooth muscles.

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