class 25 - membrane transport

types of transport acorss membrane

passive and active

passive transport

follows concentration gradient, doesn’t consume energy

active transport

goes against the concentration gradient, requires energy

ex of passive transport

diffusion, osmosis, facilitated diffusion

ex of active transport

direct and indirect

phospholipids

main component of cell membrane, function is structure and stability

glycolipids

sugar based head, main function is extracellular signaling

sterols

4 fused carbon rings, main function is membrane fluidity and permeability

uniport

one solute move one direction

symport

two solute move one direction

antiport

two solues move in opposite direction

diffusion type of

passive transport

diffusion

molcules diffuse across permeable membrane from high concentration to low concentration

osmosis type of

passive transport

osmosis

water diffuses across permeable membrane from low concentration to high concentration

issues with relying on diffusion and osmosis

cells can’t gain or lose too much water or they die, large/charged molecules need help to cross, can be too slow, unequal concentrations across memebranes are needed

facilitated diffusion is

passive transport

types of faciltated diffusion

channel and transporter

channel

forms a pore across the bilayer that can open or close non-specific and allow passage of any solute if its the right size and charge, provide chemcially favorable opening in the membrane for molecules to move through

types of channels

aquaporins and ion channels

aquaporins

non-gated water channel that facilitates rapid movement of water to maintain osmotic balance

types of ion channels

mechanical, ligated, voltage

mechanical gating

requires a force

ligand gating

requires a substrate to bind to undergo conformational change that opens the gate

voltage gated

responds to change in the electrical membrane potential

transporter

undergoes a series of conformational changes to transport small solvents across lipid bilayer, very selctive, slower rate than channels

transporter is a type of

facitilated diffusion

transporters bind and chemically

change solute to allow diffusion through membranes’ hydrophobic center

ex of bioloigcal processes that move against the gradient

uptake of essential nutrients, removal of waste, maintenance of non-equilibrium concentrations of certain ions

active transport

diffuses against concentration gradient using energy

direct is

active transport

direct

ATP dependent pumps, movement is coupled with ATP hydrolysis

indirect is

type of active transport

indirect

outcome of ATP hydrolysis leads to electrochemical environment for movements down concentration gradients, use energy from gradient or ATP for pumps to transport