Biology 2382B Lecture Notes - Lecture 15: Lipid Bilayer, Glycosylphosphatidylinositol, Signal Peptidase
28 Apr 2016
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Document Summary
They allow specialized cellular functions to occur in a localized manner. The basic components include lipids, sterols, and proteins: due to amphipathicity, phospholipids spontaneously form lipid bilayers in aqueous solution where properties of the fatty acid confer properties into bilayers. The four properties of biomembranes are fluidity, closed compartments, semi-permeable, and asymmetric: membrane fluidity. Membranes are dynamic (i. e. moving) macromolecular assemblies. They are two dimensional fluids with rapid lateral diffusion and slow transverse (flip-flop) movement (between leaflets). Fluidity can be measured by fluorescent recovery after photobleaching (frap): in this process, proteins are first fluorescently labelled. Then they are bleached by a laser at a certain area. Cytosolic face: the internal face of pm, or the external face of vesicles, Exoplasmic face: the external pm face, or internal vesicle/er/golgi/lysosome: semi-permeability. Small, uncharged, or hydrophobic molecules can pass freely. While large, hydrophilic, or charged molecuels cannot (large and charged will not go through): protein asymmetry and membrane function.
