BIOL 1201 : Exam 5
Document Summary
Importance of signaling mechanism: noble prizes, 5 in the last 18 years, when epinephrine binds to cardiac muscle cells, it speeds their contraction. When it binds to muscle cells in the small intestine, it does the opposite. How does the same hormone do different things to muscle cells: the 2 types of muscle cells have different signal-transduction pathways for epinephrine and thus have different cellular responses. Thromboxane a2 in turn stimulates vascular spasm and attracts additional platelets to the injured site. In this example, thromboxane a2 is acting as: local signal molecule. Non-polar molecules: the signal molecule leptin is 16,000 da protein. The cell membrane: assuming there is a 100 different cell signaling compounds in you. They are membrane-permeable: still highly specific, steroid signal molecules. Signal molecule binds to receptor, activates receptor, g-proteins binds to activated receptor, add gtp to it, activates g-protein molecule, g- protein molecule binds to inactive enzyme, activates enzyme.
