BIO 242 Lecture Notes - Lecture 3: Exocytosis, Nernst Equation, Osmotic Pressure
8 Oct 2016
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Document Summary
The cell membrane is a thin, flexible lipid bilayer embedded with proteins (fluid mosaic model). o. Phospholipids have a polar (electrically charged) head region and a non-polar (electrically neutral) tail region. This barrier is more the consistency of liquid cooking oil rather than solid shortening. This fluidity is maintained by cholesterol tucked in between the lipid tails of the phospholipid molecules. There is a trilaminar appearance due to the bilayer arrangement of phospholipid molecules making up the backbone of the membrane. There are specialized patches on the membrane called lipid rafts. These rafts are composed of sphingolipids rather than phospholipids, extra cholesterol, and extra proteins. These rafts are thicker than other regions of the membrane and are the sites for receptor proteins. The lipid bilayer forms the basic structural barrier that encloses the cell. Membrane proteins are inserted within, or attached to, the lipid bilayer: they can be integral proteins, embedded in the lipid bilayer (e. g. , transmembrane proteins).
