2/13/12Plasma MembraneComposed of 2 parallel sheets of phospholipids. Polar heads are exposed to the interstitial fluid and the intracellular fluids with their non polar tails in the core. Membrane proteins; integral and peripheral cholesterol stabilizes the lipid bilayer of the plasma membraneCarbohydrates attached to the phospholipid heads form glycolipidsAttached to the integral proteins to form glycoproteins. Glycolipids and glycoproteins act as signal molecule on the surface of the cell.A glycolipid/glycoprotein rich area of the plasma membrane is called the glycocalyx,makes the surface of the cell sticky and fuzzy.The glycocalyx serves several functions on the surface of the cellThe pattern/arrangement of the carbs in the glycocalyx is unique for each cell typeChanges in the glycocalyx is indicative of the cells turning cancerous.A change in the pattern allows precancerous cells to evade the new cells. The new cells can’t recognize, attack, and destroy the cancerous cells. The glycocalyx changes, other cells don’t realize it’s a bad cell. Membrane transport:Passive or active.Passive: diffusion or filtrationDiffusion: simple, facilitated, or osmosisActive: active transport of vesicular transportVesicular transport: exocytosis or endocytosisEndocytosis: phagocytosis, pinocystosis, receptor mediatedendocytosisDiffusion: the movement of solutes down their concentration gradient. Solutes movefrom areas of higher concentration to areas of lower solute concentrationSimple diffusion: lipid soluble, hydrophobic solutes. Cross the plasma membrane down their concentration gradient. Ex. Oxygen is carried by blood in blood vessels. Oxygen is released inthe capillaries, located inside tissues. Diffuses across the capillary wallinto interstitial
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