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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
plasma membrane
the plasma membrane's structure is based on a 2 ply sheet of lipid mxs ~ _____ thick
5nm
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
protein mx's
the simplest bacteria have only a single membrane-
plasma membrane
In addition to the plasma membrane euk'ic cells have a profusion of __________ that enclose intracellular compartments (organelles)
internal membranes
the lipid component of membrane consists of many millions of lipid mx's arranged in 2 close sheets, forming a-
lipid bilayer
the ______ of membrane gives it its basic structure and serves as a permeability barrier
lipid bilayer
all cell membranes are composed of _____ and _____ and share a common general strcture
lipids and proteins
thin biomx'ar sheet of mainly phospholipid mx's that forms the structural basis for all cell membranes
lipid bilayer
describe the 2 main components of a lipid mx-
1)hydrophilic (water loving) head
2)hydrophobic (water fearing) tail
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
phospholipids
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
pohsphatidylcholine
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
amphipathic
fat mx are _______, whereas phospholipids are _______
hydrophobic, amphipathic
amphipathic phosopholipids form a ________ in water
bilayer
closed spherical vesiceles, called _________ form if pure phospholipids are added to water
liposomes
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 _______
fluidity
the ease with which a cell membrane's lipid mx's move w/i the plane of the bilayer
fluidity
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
TRUE
what 2 major properties determine how tightly the hydrocarbon tails will be packed together in the bilayer-
1)length
2)degree of unsaturation
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 -
unsaturated
Hydrocarbon chain with no double bonds and has a full complement of H atoms is said to be-
saturated
t/f lipid bilayrs that contain a large proportion of unsaturated hydrocarbon tails are LESS fluid than those with lower proportions
FALSE, MORE fluid, bc each dbl bond in an unsaturated tail creates a small kink in the hydrocarbon tail
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
cholesterol
what 4 reasons makes fluidity important in a lipid bilayer?
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
cell membranes are generally ____________: they present a very different face to the interior of the cell or organelle than they show to the exterior
asymmetrical
enzymes that catalyze the transfer of lipid molecules to the opposite monolayer (from cytosolic monolayer to the opposite side)
flippases
class of lipid mx's that shows the most striking consistent asymmetric distribution in animal cells
glycolipids
in euk'ic cells nearly all new membrane synthesis occurs in one intracellular compartment-
ER
new membrane assembled in the ER is exported to other membranes of the cell through a cycle of -
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
type of lipids in animal cells that form part of a continuous surrounding protective coat of carbohydrate
glycolipids
glycolipid mx's acquire their sugar groups in the-
Golgi apparatus
are glycolipids found on the cytosolic or noncytosolic side of the lipid bilayer?
on the noncytosolic side b/c they form the protective coat of carbohydrate that surrounds most animal cells
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
inositol phospholipids, concentrated in the cytosolic half ot he lipid bilayer
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-
membrane proteins
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
TRUE, however protein's make up 50% of the mass of the membrane