CELL BIOL
Terms
undefined, object
copy deck
- 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 permeabl
- 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