A&P Lecture 5: Membrane Transport continued

carrier-mediated transport

transport proteins within the membrane carry solutes in or out of the cell

saturation

as solute concentration rises, the rate of transport rises, but only to a point

transport maximum

transport rate at which all carriers are occupied

uniport

carries one type of suite

symport

carries two or more solutes simultaneously in the same direction (cotransport)

antiport

carries two or more solutes in opposite directions (countertransport)

facilitated diffusion

carriers move solute down its concentration gradient. does not consume ATP

primary active transport

carrier moves solute through a membrane up its concentration gradient. the carrier protein uses ATP directly for energy

sodium potassium pump

each pump cycle consumes one ATP and exchanged three Na+ for two K+. keeps K+ concentration higher and Na+ concentration lower within the cell than in ECF. necessary because Na+ and K+ constantly leak through membrane.

secondary active transport

carrier moves solute through membrane but only uses ATP indirectly

vesicular transport

moves large particles, fluid droplets, or numerous molecules at once through the membrane in vesicles

endocytosis

vesicular process that bring material into cell

phagocytosis

“cell eating,” engulfing large particles

pinocytosis

“cell drinking,” taking in droplets of ECF containing molecules useful in the cell

receptor-mediated endocytosis

particles bind to specific receptors on plasma membrane

familial hypercholesterolemia

hereditary disease in which there is an abnormally low number of LDL receptors, causing cells to absorb less cholesterol than normal

exocytosis

discharging material from the cell

transcytosis

transport of material across the cell