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BIOLOGY 1A03 (746)
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Bio 1A03 chp6.docx

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Joe Kim

Chapter 6- Lipids, Membranes, and the First cells Cell membrane or Plasma membrane: layer of molecules that surround the cell Bagham used transmission electron microscopes to produce images of lipids called micrographs in 1950's. lipids: non-polars and hydrophobic -not a monomer nor polymer Steroids: -four ring structure (polar) and isoprene chain (non-polar) -ex// cholesterol Phospholipids: -glycerol,phosphate group, and 2 fatty acid chains -phospholipids containing isoprene are found in archaea -compunds that countain hydrophobic and hydrophilic regions are known as amphipathic. Phospholipid bilayers lipid bilayers: two sheets of phospholipid molecules allign micelles: when the hydrophobic tails face inwards and the heads are outwards Permeability: the tendency to allow a given substance to pass across a a membrane. Selective permeability: some molecules can pass more easily across the membrane than other (small, non-polar molecules move across the bilayers quickly) -The smaller the carbon chain and the more double bonds (unsaturated), means the more permeable the membrane is. Affect of temperature on permeability -fluidity decreases with temperature -low temperatures cause fats to solidify. Osmosis -dissolved molecules and ions are known as solutes -solutes tend to move from high concentration to a low concentration. This creates a concentration gradient. -osmosis is the movement of water in diffusion -osmosis occurs only in selectively permeable membrane -in osmosis, water moves towards the side with the higher solute concentration, evening out the density -this is important because it can swell or shrink a membrane-mound vessicle Hypertonic: water moves to outside and cell shrinks Hypotonic: water moves to inside and cell swells when both concentrations are equal is is called isotonic Membrane Proteins -In 1935 Hugh and James Danielli proposed that plasma membranes were structured like sandwhiches (polar outside, non-polar inside) -In 1972, Singer and Nicolson suggested that membrane proteins are amphipathic and the over structure was fluid and dynamic. -they are amphipathic due t
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