Ch 5-Membranes

Ch 5-Membranes - Ch 5-BIOLOGICAL MEMBRANES Size Structure...

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Ch 5-BIOLOGICAL MEMBRANES Size Structure Mosaic Model phospholipid proteins carbohydrates Membrane Functions Movement of Molecules Passive Diffusion Osmosis Filtration Facilitated diffusion Active Active Transport Connections Membranes are less than 10 nm thick, can't be seen with light microscope , are lipid bilayers FLUID MOSAIC MODEL = floating "tiles" in semi--liquid matrix phospholipids + cholesterol, proteins, carbohydrates (glycolipids, glycoproteins) Phospholipids + cholesterol H 2 O on both sides causes the phospholipids to congregate hydrophilic heads (PO 4 2 O) hydrophobic tails (hydrocarbons--non-polar--excluded by H 2 O) 1. molecules can move around--very important for functioning! 2. saturated hydrocarbon tails form Van der Waals which "gel" the matrix-less liquid 3. unsaturated chains bend causing fewer Van der Waals-more liquid, may alter % so stay liquid at low temps 4. cholesterol --although mostly hydrophobic associates with phospholipid heads (OH group), rest of molecule acts as a spacer stabilizes membrane --spacer keeps it fluid at low temps. heads held so won't be too fluid at high temps 5. resists forming free ends- makes "sacs" (vesicles) that fuse - mix contents of food vacuole and lysosome exocytosis --secretory vesicle to cell membrane and outside endocytosis --reverse process bringing things into cell Proteins - - peripheral = non-covalent bond to surface and are removed easily integral = covalent bond to lipids or proteins in membrane, usually span membrane (transmembrane), removal usually disrupts membrane functions: based on shape! 1. connection to other cells--4 kinds of connections, discuss later 2. channels --transmembrane--transport molecules across membrane 3. enzymes --catalyze reactions--hold reactants in specific orientation 4. receptors
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Ch 5-Membranes - Ch 5-BIOLOGICAL MEMBRANES Size Structure...

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