3.3 Membrane Transport

Question 1

selectively permeable

Answer 1

allows some things through (nutrients and wastes), but prevents other things (proteins and phosphates) from entering or leaving the cell

Question 2

passive mechanisms

Answer 2

transport requires no ATP expenditure by the cell; random molecular motion usually provides energy. Ex: filtration, diffusion, osmosis

Question 3

active mechanisms

Answer 3

transport uses ATP. Ex: active transport, vesicular transport

Question 4

carrier-mediated mechanisms

Answer 4

use a membrane protein to transport substances from one side of the membrane to another

Question 5

filtration

Answer 5

a process in which physical pressure forces fluid through a selectively permeable membrane

Question 6

simple diffusion

Answer 6

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

Question 7

osmosis

Answer 7

the net flow of water from one side of a selectively permeable membrane to the other

Question 8

aquaporins

Answer 8

channel proteins specialized for water

Question 9

osmotic pressure

Answer 9

the hydrostatic pressure required on one side of a selectively permeable membrane to halt osmosis

Question 10

reverse osmosis

Answer 10

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

Question 11

capillary filtration

Answer 11

the process by which the heart drives water out of the capillaries by reverse osmosis

Question 12

osmolarity

Answer 12

osmotic concentration of body fluids, expressed in milliosmoles per liter (mOsm/L)

Question 13

tonicity

Answer 13

the ability of a solution to affect the fluid volume and pressure in a cell

Question 14

hypotonic solution

Answer 14

has a lower concentration of nonpermeating solutes than the intracellular fluid

Question 15

hypertonic solution

Answer 15

has a higher concentration of nonpermeating solutes than the intracellular fluid

Question 16

crenate (v.)

Answer 16

to lose water and shrivel

Question 17

isotonic solution

Answer 17

the total concentration of nonpermeating solutes is the same as in the intracellular fluid

Question 18

normal saline

Answer 18

0.9% solution of NaCl that is isotonic to human blood cells

Question 19

carrier-mediated transport

Answer 19

a process of transporting materials through a cellular membrane that involves reversible binding to a transport protein

Question 20

saturation

Answer 20

as the solute concentration rises, the carrier’s rate of transport increases, but only up to a certain point

Question 21

transport maximum

Answer 21

the rate at which transport levels off

Question 22

uniport

Answer 22

a carrier that carries only one type of solute

Question 23

cotransport

Answer 23

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)

Question 24

symport

Answer 24

a carrier that performs cotransport

Question 25

countertransport

Answer 25

the process by which a carrier moves two or more solutes in opposite directions

Question 26

antiport

Answer 26

a carrier that performs countertransport

Question 27

facilitated diffusion

Answer 27

the carrier-mediated transport of a solute through a membrane down its concentration gradient, requiring no ATP expenditure

Question 28

primary active transport

Answer 28

a process in which a carrier moves a substance through a cell membrane up its concentration gradient using energy provided by ATP

Question 29

secondary active transport

Answer 29

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

Question 30

sodium-glucose transporters

Answer 30

proteins that simultaneously bind sodium ions (Na+) and glucose molecules and transport them into the tubule cells

Question 31

vesicular transport

Answer 31

processes that move large particles, droplets of fluid, or numerous molecules at once through the membrane

Question 32

endocytosis

Answer 32

vesicular processes that bring matter into a cell

Question 33

exocytosis

Answer 33

vesicular processes that release material from a cell

Question 34

phagocytosis

Answer 34

the process of engulfing particles such as bacteria, dust, and cellular debris

Question 35

phagosome

Answer 35

a vesicle in the cytoplasm surrounded by a unit membrane

Question 36

pinocytosis

Answer 36

the process of taking in droplets of ECF containing molecules of some use to the cell

Question 37

receptor-mediated endocytosis

Answer 37

a more selective form of phagocytosis or pinocytosis by which cells take in specific molecules from the ECF with a minimum of unnecessary matter

Question 38

transcytosis

Answer 38

transport of material across a cell (capture on one side and release on the other)

Question 39

exocytosis

Answer 39

a process of discharging material from a cell