Membrane transport mechanisms Flashcards
How do molecules move?
With kinetic energy and diffusion of molecules to areas of lesser concentration.
What is diffusion?
THe movement of molecules in the liquid and gas state. Usually from high to low concentration.
What is osmosis?
Diffusion of moleceuls from areas of high concentration to low concentration across a semi-permeable membrane.
What is osmotic pressure?
pi = gCRT; the increase in pressure on one side of a membrane than on the other side.
What are the two types of active transport?
primary and secondary
What does primary transport require?
ATPases and carrier proteins
What does secondary transport require?
carrier proteins or multiporters, which carry molecules in one direction or opposite directions.
What factors affect the rate of diffusion?
concentration differences, electric potentials and pressure differences.
What diffuses freely across a membrane?
things soluble in the phospholipid bilayer (e.g. oxgen, carbon dioxide, nitrogen)
What increases diffusion permeability?
the oil/water partition coefficient, decreased solute size and decreased membrane thickness.
What is the diffusion equation?
J=-PA(c1-C2)
What is facilitated diffusion?
diffusion that requires a uniporter carrier protein. It occurs down an electrochemical gradient and is specific for certain molecules.
What are the non-gated channels?
aquaporins, potassium & sodium channels
How many sodium and potassium ions are transported?
3 Na out, 2 K in.
What is a voltage-gated channel controlled by?
electrical potential of the membrane and binding ions.
What is a ligand-gated channel controlled by?
bonds to the membrane.
Where is the energy for secondary active transport derived from?
concentration differences of ionic substances created by primary active transport.
What occurs to two ions during secondary active transport?
One undergoes diffusion (down gradient) and the other moves against its gradient.
What type of transport does the Na/K pump use?
primary active
What type of transport does the Na/Glucose pump use?
secondary active
What type of transport do the Na/H and Na/Gluose pumps use?
secondary active
