3.3 Membrane Transport Flashcards
selectively permeable
allows some things through (nutrients and wastes), but prevents other things (proteins and phosphates) from entering or leaving the cell
passive mechanisms
transport requires no ATP expenditure by the cell; random molecular motion usually provides energy. Ex: filtration, diffusion, osmosis
active mechanisms
transport uses ATP. Ex: active transport, vesicular transport
carrier-mediated mechanisms
use a membrane protein to transport substances from one side of the membrane to another
filtration
a process in which physical pressure forces fluid through a selectively permeable membrane
simple diffusion
the net movement of particles from a place of high concentration to a place of lower concentration as a result of their constant, spontaneous motion
osmosis
the net flow of water from one side of a selectively permeable membrane to the other
aquaporins
channel proteins specialized for water
osmotic pressure
the hydrostatic pressure required on one side of a selectively permeable membrane to halt osmosis
reverse osmosis
a process in which a mechanical pressure applied to one side of the system can override osmotic pressure and drive water through a membrane against its concentration gradient
capillary filtration
the process by which the heart drives water out of the capillaries by reverse osmosis
osmolarity
osmotic concentration of body fluids, expressed in milliosmoles per liter (mOsm/L)
tonicity
the ability of a solution to affect the fluid volume and pressure in a cell
hypotonic solution
has a lower concentration of nonpermeating solutes than the intracellular fluid
hypertonic solution
has a higher concentration of nonpermeating solutes than the intracellular fluid
crenate (v.)
to lose water and shrivel
isotonic solution
the total concentration of nonpermeating solutes is the same as in the intracellular fluid
normal saline
0.9% solution of NaCl that is isotonic to human blood cells
carrier-mediated transport
a process of transporting materials through a cellular membrane that involves reversible binding to a transport protein
saturation
as the solute concentration rises, the carrier’s rate of transport increases, but only up to a certain point
transport maximum
the rate at which transport levels off
uniport
a carrier that carries only one type of solute
cotransport
a form of carrier-mediated transport in which a membrane protein transports two solutes simultaneously or within the same cycle of action by either facilitated diffusion or active transport (e.g. sodium-glucose transporter, Na+-K+ pump)
symport
a carrier that performs cotransport
countertransport
the process by which a carrier moves two or more solutes in opposite directions
antiport
a carrier that performs countertransport
facilitated diffusion
the carrier-mediated transport of a solute through a membrane down its concentration gradient, requiring no ATP expenditure
primary active transport
a process in which a carrier moves a substance through a cell membrane up its concentration gradient using energy provided by ATP
secondary active transport
a mechanism by which solutes are moved through a plasma membrane by a carrier that does not use ATP but depends on a concentration gradient established by an active transport pump elsewhere in the cell
sodium-glucose transporters
proteins that simultaneously bind sodium ions (Na+) and glucose molecules and transport them into the tubule cells
vesicular transport
processes that move large particles, droplets of fluid, or numerous molecules at once through the membrane
endocytosis
vesicular processes that bring matter into a cell
exocytosis
vesicular processes that release material from a cell
phagocytosis
the process of engulfing particles such as bacteria, dust, and cellular debris
phagosome
a vesicle in the cytoplasm surrounded by a unit membrane
pinocytosis
the process of taking in droplets of ECF containing molecules of some use to the cell
receptor-mediated endocytosis
a more selective form of phagocytosis or pinocytosis by which cells take in specific molecules from the ECF with a minimum of unnecessary matter
transcytosis
transport of material across a cell (capture on one side and release on the other)
exocytosis
a process of discharging material from a cell
