考研资料：北京大学细胞生物学第五章节物质的跨膜运输下课件幻灯片.ppt

B. Nitric oxide couples G protein-linked receptor stimulation in endothelial cells to relaxation of smooth muscle cells in blood vessels The action of Nitric oxide on blood vessels The mechanism by which acetylcholine stimulation of the endothelial cells leads to smooth muscle relaxation also explains the mechanism of action of the chemical nitroglycerin. The drug sildenafil, sold under the trade name Viagra, is an inhibitor of a cyclic GMP-specific phosphodiesterase that normally catalyzes the breakdown of cyclic GMP. 3. Signal transduction mediated by  the receptors on the cell surface A. Mediated by the Ion-Linked Receptors which convert chemical signals into electrical ones B. Signal transduction mediated by G protein-linked receptors The structure of G protein-linked receptors: Seven-helix transmembrane; C-terminal: Ser- and Thr-rich ---the sites of phosphorylation make for the desensitization of GPLR. C. Cyclic AMP signaling pathway The activation of protein kinase A by cyclic AMPs The mechanisms that shut off a signal are as important as the mechanisms that turn it on. D. The pathway through phospholipase C results in a rise in intracellular Ca+ IP3-Ca2+ pathway and DG-PKC pathway E. Receptor tyrosine kinase (RTK) and  RTK-Ras signaling pathway RTK are the second major type of cell-surface receptors Ligand binding leads to autophosphorylation of RTK MAP-kinase serine/threonine phosphorylation Pathway activated by Ras 5. Convergence, divergence, and crosstalk among different signaling pathway A. Convergence: Signals from a variety of unrelated receptors can converge to activate a common effector. B. Divergence: Signals from the same ligand can diverge to activate a variety of different effectors. C. Crosstalk: Signals can be passed back and forth between different pathways 6. In actual fact, signaling pathways in the cell are much more complex. 1.The mechanical-structural function of focal adhesion, which is carr