BIOL 3202 Lecture Notes - Lecture 6: Sterol, Hydrophile, List Of Bus Routes In Queens
25 Oct 2017
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Document Summary
Membrane phospholipids assemble spontaneously into bilayers when placed in water, forming closed junctions that reseal if torn: the fluid-mosiac model is the central dogma of membrane biology. Individual lipid molecules in a lipid bilayer are able to diffuse within their own monolayer but cannot spontaneously flip from one monolayer to the other because this is energetically unfavorable. Scramblases and flippases are proteins that catalyze the flipping of lipid molecules from one leaflet to another: membrane assembly begins in the er. Enzymes attached to the cytosolic face of the. Er deposit newly made phospholipids exclusively into the cytosolic half of the bilayer. Flippases and scamblases also contribute to the creation and maintenance of leaflet asymmetry: there are three major classes of membrane lipid molecules: phospholipids, sterols, and glycolipids. The major phospholipid in cell membranes is phosphatidycholine. The major sterol in animal cell membranes is cholesterol. Animal cells do this by primarily by altering the amount of sterol (cholesterol).
