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36 Cards in this Set
- Front
- Back
cell is a self reproducing system of mx's held inside a __________-a fatty thin and transparent film
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plasma membrane
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the plasma membrane's structure is based on a 2 ply sheet of lipid mxs ~ _____ thick
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5nm
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to facilitate exchange inward and outward of a cell, the membrane is penetrated by highly selective channels and pumps- ________ that allow specific substances to be imported while others are exported
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protein mx's
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the simplest bacteria have only a single membrane-
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plasma membrane
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In addition to the plasma membrane euk'ic cells have a profusion of __________ that enclose intracellular compartments (organelles)
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internal membranes
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the lipid component of membrane consists of many millions of lipid mx's arranged in 2 close sheets, forming a-
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lipid bilayer
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the ______ of membrane gives it its basic structure and serves as a permeability barrier
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lipid bilayer
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all cell membranes are composed of _____ and _____ and share a common general strcture
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lipids and proteins
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thin biomx'ar sheet of mainly phospholipid mx's that forms the structural basis for all cell membranes
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lipid bilayer
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describe the 2 main components of a lipid mx-
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1)hydrophilic (water loving) head
2)hydrophobic (water fearing) tail |
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the most abundant lipids in cell membranes are the _________, mx's in whicht eh hydrophilic head is linked to the rest of the lipid thru a phosphate grp
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phospholipids
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most common type of phospholipid in most cell membranes is ____________, where the small mx choline attached to a phosphate as its hydrophilic head and 2 long hydrocarbon chains as its hydrophobic tails
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pohsphatidylcholine
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mx's with both hydrophilic and hydrophobic properties are termed-________, which play a crucial role in driving these lipid mx's to assemble into bilayers
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amphipathic
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fat mx are _______, whereas phospholipids are _______
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hydrophobic, amphipathic
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amphipathic phosopholipids form a ________ in water
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bilayer
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closed spherical vesiceles, called _________ form if pure phospholipids are added to water
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liposomes
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lipid mx's within a monolayer continuously exchange places with their neighbors, if this happens at a high rate (usually in higher temperatures) it is said to have a high _______
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fluidity
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the ease with which a cell membrane's lipid mx's move w/i the plane of the bilayer
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fluidity
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t/f the closer and more regular the packing of the hydrophobic tails of a amphipathic lipid, the more viscous and less fluid it will be
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TRUE
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what 2 major properties determine how tightly the hydrocarbon tails will be packed together in the bilayer-
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1)length
2)degree of unsaturation |
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Hydrocarbon chain that harbors a dbl bond and not contain the max number of H atoms that it could in principle is said to be -
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unsaturated
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Hydrocarbon chain with no double bonds and has a full complement of H atoms is said to be-
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saturated
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t/f lipid bilayrs that contain a large proportion of unsaturated hydrocarbon tails are LESS fluid than those with lower proportions
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FALSE, MORE fluid, bc each dbl bond in an unsaturated tail creates a small kink in the hydrocarbon tail
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in animal cells membrane fluidity is modulated by the inclusion of the sterol- that fill the spaces b/t neighboring phospholipid mx's left by the kinks in their unsaturated hydrocarbon tails, stiffening the bilaryer making it more rigid and less permeable
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cholesterol
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what 4 reasons makes fluidity important in a lipid bilayer?
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1)allows membrane proteins to diffuse rapidly in plane of bilayer and interact w/ eachother
2) permits lipids and proteins to diffuse from sites where they're inserted into bilayer, after a synthesis in another part of the cell 3)allows membranes to fuse w/ one another and mix their mx's 4)ensures membrane mx's are distributed evenly b/t daughter cells when a cell divides |
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cell membranes are generally ____________: they present a very different face to the interior of the cell or organelle than they show to the exterior
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asymmetrical
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enzymes that catalyze the transfer of lipid molecules to the opposite monolayer (from cytosolic monolayer to the opposite side)
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flippases
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class of lipid mx's that shows the most striking consistent asymmetric distribution in animal cells
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glycolipids
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in euk'ic cells nearly all new membrane synthesis occurs in one intracellular compartment-
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ER
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new membrane assembled in the ER is exported to other membranes of the cell through a cycle of -
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vesicle budding and fusion- bits of membrane pinch off from the ER to form small vesicles, wheich then become incorporated into another membrane by fusing with it
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type of lipids in animal cells that form part of a continuous surrounding protective coat of carbohydrate
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glycolipids
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glycolipid mx's acquire their sugar groups in the-
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Golgi apparatus
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are glycolipids found on the cytosolic or noncytosolic side of the lipid bilayer?
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on the noncytosolic side b/c they form the protective coat of carbohydrate that surrounds most animal cells
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these are minor components of the plasma membrane, that play a special role in relaying signals from the cell surface to the intracellular components that respond to those signals
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inositol phospholipids, concentrated in the cytosolic half ot he lipid bilayer
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most membrane fuctions are carried out by ________, where in animals, they constitute ~50% of th emass of most plasma membranes, the remainder being lipid plus relatively small amounts of carbohydrate-
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membrane proteins
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t/f bc lipid mx's are much smaller than protein mx's, a cell membrane typically contains about 50 times more lipid mx's than protein mx's
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TRUE, however protein's make up 50% of the mass of the membrane
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