BISC207 Lecture Notes - Lecture 8: Lipid Bilayer, Polar Regions Of Earth, Membrane Transport
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25 Sep 2018
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Hydrophilic heads in each layer face a surrounding solution. The hydrophobic tails face one another inside the bilayer. Vesicles can form phospholipids in the lab. Many factor influence the behavior of the membrane. Number of double bonds between the carbons in the hydrophobic tail. Number of cholesterol molecules in the membrane. Bond saturation and hydrocarbon chain length affect membrane fluidity and permeability. Double bonds in a hydrocarbon chain can cause a kink in the hydrocarbon chain. Cholesterol: largely nonpolar with a tiny polar region by the hydroxyl group (oh-) Adding cholesterol to membranes increases the density of the hydrophobic section. Small or nonpolar molecules move across phospholipid bilayers quickly. Charged or large polar substances cross slowly, if at all. Barrier to hydrophilic molecules and ions due to hydrophobic interior. Gases and a few small, uncharged molecules can passively diffuse across. Ions and large polar molecules diffuse slowly. The fluid-mosaic model of membrane structure suggests.