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Jan 12th - The Plasma Membrane & Cellular Transport

Jan 12th - The Plasma Membrane & Cellular Transport -...

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The Plasma Membrane & Cellular Transport Jan 12 th Fluid mosaic model of membrane structure Plasma Membrane - defines extent of cell; fragile selective, semi-permeable barrier. Phospholipid layer – has phospholipid hairs on the outside of the cells, and the heads on the inside of the side (they are hydrophobic: scared of water, move away from water) Plasma membrane considered a fluid Phospholipids o Glyercol backbone with two fatty acids+phosphate containing groups o Made of glycerol, long chain fatty acids: most of them are poly unsaturated fatty acids, with at least 2 or more double bonds o Poly unsaturated fatty acids = increase membrane fluidity o Saturated fatty acids = more stable, less fluid, involved in cell signaling ( lipid rafts) o Lipid rafts involved in receptor mediated signal transduction o Cholesterol Mosaic structure of plasma membrane – proteins dispersed in the lipid bilayer those that are no anchored constantly change their position. Proteins Two classes of membrane proteins 1. Integral membrane proteins – embedded within 2. Perpherial membrane protein – loosely attached Function Transport Enzymatic activity Receptors for signal transduction – cannot bind to the cell Intercellular joining – form hooks to make sure they are attached, glycoproteins works like Velcro Cell-cell recognition Attachment to the cytoskeleton and extracellular matrix Carbohydrates Located primarily on membrane outer surface Bound to plasma lipids or proteins ( glycolipids & glycoproteins) Overall function of membrane Protects cells from external environment, cell barrier only letting some things in and some things out Cellular joining, attachment and communication Transport, membrane semi-permeable – lipid layer, fat acids, and vitamins (A,C,K,D) can move through the phospholipid bilayer easily
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