Question

Assignment 1 Review Email i and then write an email to Tess identifying the first messenger that starts the signal transduction in the smooth muscle cell, the likely second messenger, and finally the cellular response caused by the cell signaling cascade. Explain why the arrows go from small to bigger. Also identify whether the receptor that starts the cell signaling pathway is in the plasma membrane or intracellular. Assignment 2 Review Email 2 and then answer the following questions: 1. Melody said that ginseng enhances erection. What effect would you expect ginseng to have on nitric oxide? Why? 2. Knowing that Melody said Viagra also enhances erection, what effect would you expect it to have on PDE5? Why? 3. If neither chemical works what protein(s) would you suspect is “broken”?

Answer 1

the first messenger that starts the signal transduction in the smooth muscle cell is Nitric Oxide. Nitric oxide is a compound produced by many cells of the body. It relaxes vascular smooth muscle by binding to the heme moiety of cytosolic guanylate cyclase, activating guanylate cyclase and increasing intracellular levels of cyclic-guanosine 3',5'-monophosphate, which then leads to vasodilation. Thus the second messenger is GMP.  

Guanylyl cyclase receptors are transmembrane proteins of the plasma membrane that exist as dimers in their active form. They contain both a ligand-binding site in an extracellular domain and an intracellular domain that catalyzes the cyclization of GTP into cGMP.

Arrows become bigger as there is amplification of signal transduction at every step.