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24 Cards in this Set
- Front
- Back
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what are the 3 basic constituents of membranes?
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phospholipids, glycolipids, cholesterol
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micelle
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made up of fatty acids--polar heads face water, hydrophobic tails associate (forms circle)
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liposome
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prototype of cell--has lipid bilayer made of phospholipids, tiny bubbles that can deliver drugs, etc.
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why do phospholipids form a bilayer instead of a micelle?
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2 fatty acid chains are too bulky to fit into a micelle
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how does cholesterol regulate membrane fluidity?
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at high temps, it reduces membrane fluidity by interacting with hydrocarbon tails of phospholipids, at low temps, it prevents gelling
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what are the 3 basic constituents of membranes?
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phospholipids, glycolipids, cholesterol
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micelle
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made up of fatty acids--polar heads face water, hydrophobic tails associate (forms circle)
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liposome
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prototype of cell--has lipid bilayer made of phospholipids, tiny bubbles that can deliver drugs, etc.
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why do phospholipids form a bilayer instead of a micelle?
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2 fatty acid chains are too bulky to fit into a micelle
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how does cholesterol regulate membrane fluidity?
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at high temps, it reduces membrane fluidity by interacting with hydrocarbon tails of phospholipids, at low temps, it prevents gelling
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lipids are asymmetrically distributed: what lipids are found in outer leaflet? inner leaflet?
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outer: sphingomyelin, phosphotydilcholine
inner: phosphotydilethanolamine, phosphotydilserine |
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most common structural motif in membrane proteins
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alpha-helices
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hydropathy
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index indicating hydrophobicity of amino acid--higher the number, the more hydrophobic
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uniporter
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transport of one substrate in either direction depending on concentration gradient
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secondary transporters
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(aka co-transporters)--a concentration gradient in compound A drives simultaneous transport of another compound (antiporters or symporters)
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3 types of channels
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voltage gated
ligand gated gap junctions |
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Shaker K+ Channels
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channel opens and closes in response to changes in membrane potential; has selectivity filter that excludes all ions except K+
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Why can K+ pass through K+ channels, but not the smaller Na+?
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ionic radius doesn't consider hydration shell--hydrated ions are much bigger
interactions of K+ ions with selectivity filter carbonyl groups give energy to strip away hydration shell--Na+ interactions don't provide enough energy |
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aquaporins
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channels that allow transport of water at a faster rate than normal diffusion
-hydrophilic residues line channel -present in epithelia (kidney, cornea) |
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connexins
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major gap junction proteins
mutations in a connexin are associated with most forms of hereditary deafness |
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what does bungarotoxin affect?
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Ach receptor
from snakes |
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what is tetrodotoxin?
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toxin in puffer fish, inhibits Na+ channels
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what is digitalis?
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comes from plants
inhibits Na-K pump |
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ligand-gated ion channels
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ex. acetylcholine receptor
cation channel equally permeable to Na+ and K+ is gated by binding of ligand, acetylcholine binding of acetylcholine causes alpha-hylical rods (hydrophobic) lining pore to rotate so that pore is lined by small polar residues (Ca+ passes through and causes muscle contraction) |
