Structure/Function of membrane transport system Flashcards
(20 cards)
passive mediated transport is mediated by
ionophores, porins, ion channels, aquaporins, and transport proteins
ionophores
may carry ions or form channels
porins
provide a passage for ions and non-polar substances
ion channels
highly selective and may be gated
aquaporins
mediate the transmembrane passage of water molecules
transport proteins
may mediate uniport, symport, and antiport transport.
ABC transporters move ?
amphipathic substances from one side of the membrane to the other
how does secondary active work?
it uses the existing ion gradient to drive unfavorable transport of a second substance
how does non-mediated occur
through simple diffusion. This is done also for steroids and oxygen
what substances use mediated transport
ionic and polar substances.
facilitated diffusion (passive mediated transport) works by
A specific molecule flows from high concentration to low concentration.
active transports works by
A specific molecule is transported to high concentration, against its concentration gradient. Such an endergonic process must be coupled to an exergonic process so that G<0.
what are the 2 kinds of ionophores
- carrier ionophore
- channel forming ionophore
an example of carrier ionophore is
valinomycin. It has 10K more affinity for K than for Na
list the 4 types of gating for ion channels
mechanosensitive
ligand gated
signal gated
voltage gated
when are gap junctions fully open?
fully open when [Ca2+]<10^-7M and become narrower as [Ca2+] increases. When [Ca2+]>5x10^5M they close (to protect neighboring cells from damage propagation)
GLUT 1 is a
uniport
ATP-ADP translocator is a
antiport
the alpha chain and the beta chain in Na-K -ATPase function as
- alpha chain: is responsible for the functional activity of the pump.
- beta chain: facilitates the correct insertion of the a subunit into the plasma membrane.
what are cardiac glycosides? And their functions?
digitalin, ouabain.
They bind the (Na+-K+)-ATPase and block it at step 5. This causes an increase in intracellular [Na+] that stimulates the (Na+-Ca2+) antiport system, which pumps Na+ out of and Ca2+ into the cell, thus boosting [Ca2+] in the sarcolemma reticulum. The release of Ca2+ to trigger muscle contraction produces a larger than normal increase in cytosolic [Ca2+], thereby intensifying the force of cardiac muscle contraction.
