Transport of substance through cell Membranes Flashcards
the two type of membrane proteins are?
channel proteins and carrier proteins
what are channel proteins?
watery spaces all the way through the molecule, allows diffusion of water and selected molecules and ions
what are carrier proteins?
they mind with molecules and have conformational change in their protein molecule then move the substance to the other side of the membrane.
what is different in active transport than in normal diffusion?
active transport takes place with the help of carrier proteins against the concentration gradient
define simple diffusion?
diffusion through membrane opening or intracellular space without interaction with carrier proteins.
rate of diffusion is determined by?
amount of substance available
the velocity of kinetic motion
number and size of membrane openings
define facillated diffusion ?
diffsuion with the help of carrier protein
the pores that allow rapid movement of water through cell membrame are ?
aquaporins
example of aquaporins in book?
erythrocytes
describe the structure of potassium channel?
tetrameric with 4 identical protein subunits surrounding a central pore. has pore loops on the top of channel pore that has selectivity filter.
what does the selectivity filter of potassium channels have ?
carbonyl oxygens
function of carbonyl o2?
it dehydrates the k+ ions and allows it to past the channel
diameter of NA channels?
0.3 to 0.5
selectivity filter of NA ions have?
negatively charged amino acids
what does the -ve charged amino acids do?
they attarcted the small dehydrated Na Ions from the surrounding hydrating water molecules.
the opening and closing of gates is operated in what two ways?
- voltage gating
2. chemical ligand gating
what charge on the inside makes the Na gated to be closed?
-ve on the inside
what charge on the inside makes the K+ gates to be open?
+ve charge on the inside
example of chemical gating?
acetylcholine
the pore that acetyl choline opens is what diameter and allows what ions to move past?
0.65 nanometer and allows +ve and uncharged ions to pass through
the difference between simple diffusion and facillated diffusion?
the rate of simple diffusion increases with the concentration of the diffusing substance but facilated diffusion reaches Vmax and stops.
the rate at which the substance diffuse inwards in equal t0?
concentration of the substance to the outside
rate of net diffusion?
concentration of inside - concentration of outside
what the nernst equation ?
the electrical diff that will balance out the concentration diff of univalent ions can be determend by nernst equation.
