Structure/Function of membrane transport system Flashcards
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.
