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What are lipids (definition)?
catch all term for carbon containing compounds that are found in organisms and are largely nonpolar and hydrophobic (do not dissolve in water)
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Saturated
hydrocarbon chains without double bonds (straight) saturated with maximum number of hydrogen atoms that can attract
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Unsaturated
has double bond (bent), fewer than maximum number of hydrogen’s are attached
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What is membrane permeability? What factor effect permeability?
- Permeability = tendency to allow a given substance to pass through it. Membrane have polar, hydrophilic region
- Number of double bonds in hydrophobic tail, overall length, number of cholesterol molecules nearby
- Lipid bilayers containing many unsaturated fatty acids have more gaps and should be more permeable than bilayers with few unsaturated fatty acids
- More permeable with short, unsaturated hydrocarbon tails. Long strait saturated fatty acid tails less permeable
- Adding cholesterol molecules to liposomes dramatically reduces the permeability of the lipid bilayers
- Low temperatures lower permeability, molecules in bilayer move more slowly, pack together, begin to solidify
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Diffusion
spontaneous movement of a substance from a region of high concentration to one of low concentration, down concentration gradient
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Osmosis
diffusion of water across a selectively permeable membrane from a region of high concentration (low solute concentration) to a region of low water concentration (high solute concentration)
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Can you look at a molecule and know its likely permeability?
- Small, nonpolar molecules move across bilayers quickly. Large molecules and charged substances cross membrane slowly, if at all.
- Charged compounds and large, polar molecules cant pass through the nonpolar, hydrophobic tails of a lipid bilayer
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Hypertonic
- solution has a greater solute concentration and lower water concentration
- Cell shrink and membrane shrivel
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Hypotonic
- solution that has lower solute concentration, higher water concentration
- Cell will swell or burst
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Isotonic
- concentrations equal on either side of the membrane
- Does not affect membrane’s shape
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Integral membrane proteins
any membrane protein that spans the entire lipid bilayer (transmembrane protein)
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Peripheral membrane proteins
does not span the entire lipid bilayer and associates with only one side of the bilayer (attached to transmembrane)
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Transport protein
aby membrane protein that enables a specific ion or small molecule to cross a plasma membrane. Includes carrier proteins and channel proteins, which carry out passive transport (facilitated diffusion), and pumps, which carry out active transport.
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Ion channels
type of channel protein that allows certain ions to diffuse across a plasma membrane down an electochemica gradient
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Channel protein
forms a pore in a cell membrane. Structure of most allows them to admit just one or a few types of ions or molecules
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Aquaporin
allow water to cross the plasma membrane over 10 times faster without
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Carrier proteins
(transporters) – membrane protein that facilitates diffusion of a small molecule (glucose) across the plasma membrane by a process involving a reversible change in the shape of the protein (facilitated diffusion)
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Pumps
membrane protein that can hydrolyze ATP to power active transport of a specific ion or small molecule across a plasma membrane against its electrochemical gradient (sodium-potassium pump) 3 NA/ 2 K
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