chapter 5 - plasma membranes Flashcards
what is compartmentalisation
the formation of seperate membrane-bound areas
what is the fluid mosaic model
phospholipids are free to move giving the membrane flexibility and because the proteins embedded in the bilayer vary in shape, size and position
what are intrinsic proteins
proteins embedded through both layers of a membrane.
what are the 2 types of intrinsic proteins
channel proteins - provide hydrophilic channel that allows passive movement of polar molecules
carrier proteins - used for both passive and active transport
what are glycoproteins
intrinsic proteins with carbohydrate chain attached
what are uses of glycoproteins
used in cell adhesion
receptor for cell signalling
what are glycolipids
lipids with attached carbohydrate chain. these molecules are called antigens
what are extrinsic proteins
proteins present in one side of the bilayer
what is cholesterol
a lipid with hydrophilic end and hydrophobic end which interacts with phophate head and fatty acid tail pulling them closing to stabilise membrane
regulates fluidity of membrane by preventing membrane to group too closely
factors affecting membrane structure
temperature
solvents - non-polar like alcohol dissolve membranes
what is diffusion
diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration
what are the factors affecting rate of diffusion
temperature
concentration difference
what is simple diffusion
diffusion in absence of a barrier
why are membranes partially permeable
only small non-polar molecules can freely diffuse through
what are the factors affecting rate of diffusion across a membrane
surface area
thickness of membrane
what is facilitated diffusion
diffusion of particles across a membrane through protein channels
why are membranes with protein channels selectively permeable
most protein channels are specific to one ion/molecule
factors affecting facilitated diffusion
temperature
concentration difference
surface area
thickness of membrane
number of protein channels
what is active transport
movement of particles from a region of lower concentration to a region of higher concentration. this requires energy and carrier proteins
how does carrier proteins act as pumps
molecule to be transported binds on receptors of carrier protein. ATP on inside of cell binds to carrier protein and is hydrolysed to ADP and phophate which binds to carrier protein , opening it up. Molecule is released into cell and phophate is now released so carrier protein closes up and recombined with adp to form atp
what is bulk transport
form of active transport for large molecules such as enzymes and hormones
what is endocytosis
bulk transport of material into cells
what are the 2 types of endocytosis
phagocytosis ( solid)
pinocytosis ( liquid)
what is exocytosis
bulk transport of material out of cells
what is osmosis
diffusion of water across a partially permeable membrane
what is water potential
pressure exerted by water molecules as they collide with a membrane
what is water potential of pure water
0
what is cytolysis
bursting of animal cell due to increased hydrostatic pressure as they have no cell wall and cannot stretch much
what is crenation
when animal cell loses water resulting in reduction of volume
how is cytolysis and crenation prevented
animal cells have isotonic solution such as blood plasma for equal water potential
why dont plants burst as much as animal cells
have cell wall so can withstand higher pressure ( turgor) which prevents entry of more water ( turgid)
what is plasmolysis
lower water potential in plant cell so cell shrinks and protoplast is pulled against cell wall and shrinks
