BIOL 372 Lecture Notes - Lecture 1: Cholera Toxin, Adenylyl Cyclase, Hypovolemia
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Vs why?: proximate- refers to explanations that deal with the mechanics of life process. This explains the mechanism: ultimate- refers to explanations that deal with evolutionary origins (survival and reproduction) Why organisms have the characteristics they have. Why natural selection has generated the characteristics, why do the characteristics enhance survival and or reproduction: an example of proximate vs ultimate- the causation of cholera by the bacterium, vibro cholerae. Principal manifestation of cholera: watery diarrhea which can cause severe dehydration and may kill infected individuals. Cholerae secretes a toxin (ct) that causes fluid efflux from the cells that lines the intestinal tract. Ct is composed of an a subunit and a b subunit. The b subunit attaches to gm 1 ganglioside which protrudes from the membrane of the cells that line the small intesting. The ct/gm1 complex is brought into the cell through endocytosis. The a subunit of ct is cleaved from the b subunit.
