BIO 203 Lecture Notes - Lecture 2: Symporter, Uniporter, Animal
8 Dec 2017
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Ta(cid:454)o(cid:374)o(cid:373)ic li(cid:374)eages evolved (cid:373)ulticellularit(cid:455) a(cid:374)d is(cid:374)"t li(cid:373)ited to eukar(cid:455)otes. The challenges of metazoan (and multicellular) life large size -> long diffusion distances -> vascular system for bulk transport. Subdivision of organismal functions -> tissues and organs. Multiple compartments/spaces: unicellular organism: intraorganellar spaces, intracellular space, multicellular organism: intraorganellar spaces, intracellular space, interior extracellular spaces, interstitial space, intravascular space, exterior space. Major physiological challenge: integration and coordination of functional activities across the organism for optimal fitness in the real environment. Membranes perform a barrier function, separating compartments/spaces. Protei(cid:374)s do(cid:374)"t (cid:373)o(cid:448)e due to the (cid:373)e(cid:373)(cid:271)ra(cid:374)e"s fluidly. But material exchange is essential to cellular and organismal life. Molecules above absolute zero temperature are in motion. The velocity of movement is proportional to temperature. The probability that a molecule will cross an interface is, therefore, proportional to both temperature and concentration. Consider that diffusion occurs in both directions (compartment 1 compartment 2, j12; and compartment 2 compartment 1, j21).
