10.4.2006 - D Methods for getting across = transport 1...

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5/7/2009 II. D. Phospholipids: cellular membrane bilayer 1. Phospho / glycerol head +2 fatty acid tails (one saturated, one unsaturated) 2. heads are hydrophilic and the tails are hydrophobic BIOLOGICALMEMBRANES: FLUID MOSAIC MODEL I. Characteristics: A. Fluid: unsaturated H-C tails of phospholipids and cholesterol molecules keep membrane fluid at normal body temperature; phospholipids bilayer results in aqueous solution B. Mosaic: proteins embedded in bilayer 1. determine function of membrane 2. each membrane type has its own special protein gang 3. Integral proteins= transmembrane proteins: span the bilayer 4. Peripheral proteins = cell surface proteins: attached either to the outside or inside of the bilayer C. Selective permeability 1. Some stuff can enter the cells easily, some stuff can’t a. Hydrophobic tails impeded hydrophilic substances b. Small, slightly polar molecules (H2O), for example can diffuse c. Large macromolecules and ions need help getting across
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Unformatted text preview: D. Methods for getting across = transport 1. passive: no energy needed, things move along their concentration gradient a. diffusion: concentration gradient b. Osmosis: diffusion of H2O only-Osmotic concentration: solutions made up of 2 parts: water and solutes-If a solution contains more solutes than water, it is a hypertonic solution -If a solution contains less solutes than water, it is hypotonic solution-Isotonic solution c. Facilitated diffusion: transport proteins provide a channel (pore) for medium size molecules or ions. 2. Active: energy needed because things are being moved against their concentration gradient 3. Movement of large proteins, polysaccharides a. Exo-cytosis: removal b. Endo-cytosis: bringing-in II. Functions A. Define cell boundaries B. Organize internal cell structure C. Mediate cellular interations membrane proteins...
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