membrane transport

membranes __ the contents of the cell from the extracellular space

separate

membranes __

keep the contents of the organelles separate from the cytoplasm

what molecukes cab diffuse through the mem

small non polar & small uncharged polar

in endocytosis and exocytosis what are formed

pits with receptors

what interacts with the receptor

ligands

phagocytosis

food

pinocytosis

dissolved material

most molecule carriers are

integral trans membrane proteins that span the membrane

what molecules dont require transporters

non polar and gasous

what molecules need transporters

charged and big molecules

simple diffusion is

non polar compunds traveling down conc gradient

facilitated diffusion travels

down electro chem graident

proteins in facilitated diffusion provide

safe passage

facilitated diffusion is thermodynamically

favorable (-G)

ion channels allow molecules to travel

down their conc gradient

ion channels can be

gated by a ligand or ion

ion channels are

specific to ions

ionophormediated ion transport travels

down the conc graditn

ionophore is

protein that binds ions and diffuses through mem

primary active transport travels

against conc gradient

how does primary active transport allow ions to travel against conc gradient

it is coupled to ATP hydrolysis

primary active transport is

not favorable (+G)

secondary active transport travels

against conc gradient

what drives sencondary active transport

another ion moving down its own gradient

transport of the molecule in secondary active transport is done by

another ion moving down its gradient

how was the 2nd ion gradient made

by ATP

secondary active transport is not

directly linked to ATP

passive transport uses

chemical gradient for energy

non mediated passive transport

occurs through simple diffusion

mediated passive transport

leads to much higher transport rates than simple diffusion

meditated passive transport used

specific transport proteins

both mediated and non mediated pasive transport involve

flow of molecules down gradient from high --> low

the free energy of a solute depends on its

conc

in mem transport solutes move from

higher conc to lower conc

at eq

[o]1 = [o]2 the rate of transport in both directions is equal

if favorbale

solute travels from high to low

if non favorable

solutle moves from low to high and requires energy input

what are also affected by mem potential

charged molecules

non mediated transport is with

small hydrophobic compounds that can diffuse across membrane

rate of transport

Ja= Pa([A]out-[A]in)

ja

rate of transport

[A]out-[A]in

conc gradient

Pa

perm coeffiecent of A in the membrane =Da/x

facilitated diffusion is how

bigger molecules get into cells

in faciitated diffusion G is

< 0 but proteins assist

in facilitated diffusion solute only move in

the thermodynamically favored direction along the conc gradient

in facilitated diffusion proteins may

"facilitate" transport increasing the rates of transport

2 important distinguishing featured of facilitated diffusion

solute flows in the favored direction

transport displays saturation kinetics

glucose transporter in facilitated diffusion are

selective to glucose and faster than simple diffusion

glucose crosses mem via

a transport protein

cannot rely on

simple diffusion for glucose

in both simple and facilitated diffusion molecules move

from high to low conc

simple diffusion is

slow and not saturated

facilitated diffusion is

faster and can be saturated

what does saturated mean

all transporters are occupied and it cannot move any faster

red blood cell mem has

glucose permease

glucose permease

rapidly and specifically transports glucose

how does glucose permease work

not a hole in mem, gated pore mechanism

glucose permease has __ conformations

2

GLUT 1

transport of glucose across the blood brain barrier

GLUT 1

is not as fast

GLUT 2

glucose sensor in pancreatic B cells

GLUT 3

glucose transport in neurons also expressed in tissues with high demand for glucose

when glucose conc is low

GLUT 3 will be active

GLUT 4

skeletal muscle, adipose tissues, the only insulin sensative isoform

when glucose conc is low

GLUT 4 is not active