Plasma Membrane Transport

what is the main way in which most molecules move?

diffusion

define diffusion.

mvmt from a region of high concentration to a region of low concentration (downhill)

define a passive process (with an example).

does not require energy investment

• ex: diffusion

at what point does a solution reach equilibrium?

when particles are uniformly distributed

when equilibrium is reached, there will be…

equal concentration of solute trhoughout

molecules will move across what to reach equilibrium.

the plasma membrane

define selective permeability and its paramaters.

mvmt across lipid bilayer dependent on

• charge/polarity

• size

how do large molecules enter the cell?

transported by a carrier mechanism

how do lipid soluble molecules enter the cell?

diffusion thru plasma membrane

how do small water-soluble molecules enter the cell?

diffuse through membrane channels

how do ions enter the cell?

diffuse through membrane channels

define simple diffusion.

movement of freely permeable solutes across membrane from region of high to low conc.

• NO NEED of transport proteins

give an example of simple diffusion.

mvmt of O2 and CO2 from blood plasma into cells

define facilitated diffusion.

mvmt from high to low conc. with assistance of integral protein

facilitated diffusion does NOT require ____

ATP

what are two examples of facilitated diffusion

• glucose family of transporters (GLUT)

• epithelial sodium channels (ENaC)

how does GLUT work?

solute binds to carrier protein (GLUT) and creates a conformational change

how does ENaC work?

its an open pore that allows NA+ to move into the cell

what are channels?

membrane protein that forms a channel to pass thru

what are non-gated channels?

membrane protein that forms an aqueous passageway

• always open

what’s another name for non-gated channels?

pores

what are gated channels?

membrane protein that forms an aqueous passageway

• intermittently open/closed

define carriers.

membrane proteins that bind substance at one end → undergoes conformational change → transports substance to other side of membrane

define active transport.

mvmt of solute from region of low conc. to high conc.

• against nature

• “uphill”

what is the advantage of active transport?

it does not depend on conc. gradient

what is the source of energy for mvmt across the membrane?

ATP

define ATPase.

enzyme that hydrolyzes ATP to yield ADP + P_i

in primary active transport, ATP is ____ coupled to solute mvmt.

directly

in secondary active transport, ATP is ____ coupled to solute transport.

indirectly

what are the two types of secondary active transport?

co-transport (symport) and counter-transport (antiport)

define symport.

both solutes move in same direction

define antiport.

solutes move in opposite directions

give an example of secondary active transport

glucose takes advantage of Na moving into cell and follows its conc. gradient

• then use ATP to pump out unwanted Na

define osmosis.

passive mvmt of water through a semi permeable membrane

water moves across membrane bc of differences in conc. of ____ ____ on either side

impermeant solute

water moves from region of blank to blank

low solute conc., high solute conc.

what does osmolarity measure?

measurement of dissolved particles

what is a force that prevents water from moving?

hydrostatic pressure

define aquaporins

integral membrane pore proteins which allow water to pass

where does the majority of water move into and out of cells from?

aquaporins

define pinocytosis.

“cell drinking”

what is normal osmolarity?

300

what is the colligative property?

dependent on total number of particles in a given amount of solution

• NOT dependent on size, charge, type of particle

define isosmotic.

two solutions that have the same osmolarity

the solution with the higher osmolarity is ____.

hyperosmotic

the solution with the lower osmolarity is ____

hyposmotic

out of ECF and ICF, which is hyper/hyposmotic?

ECF: hyper

ICF: hypo

define hydrostatic pressure.

the fluid pressure of water inside its vessel

• can oppose osmotic pressure

• can limit mvmt of water

what happens to a cell in a hypotonic solution?

mvmt of water into cell → swelling

what happens to a cell in a hypertonic solution?

mvmt of water out of cell → shrinking + crenated