BISC 313 Lecture Notes - Lecture 12: Fluid Mosaic Model, Lipid Bilayer, Toxicokinetics
21 Feb 2019
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Several sites for 1st contact btwn a xenobiotic and an organism. Regardless of site, chemical has to pass thru biological membrane to exert its toxic effect: exceptions: caustic agents (acids/bases) (cause problems on surface of cells) Fluid mosaic model: lipid bilayer, associated proteins, whole system is dynamic, some regions are more rigid. Selectively permeable: allow certain things thru, most cases it"s a barrier, compartmentalizing the cell (as a whole, and organelles) Only lipophilic materials will move into or through membrane on their own: exceptions: water (so small it can squeeze through, xenobiotics are similar to endogenous molecules, polarity/charged (charged wont move thru membrane) eg. na+ (sodium channels) Five ways to pass through membrane: filtration, passive diffusion, most important mechanism for environmental chemicals (generally, eg. pcbs, pesticides, industrial chemicals (hexachlorobenzene, no barrier, all hydrophobic, dissolve through with ease unless they"re too big. That"s why we"re concerned most with these, because they can just go right in.
