Structure/Function of membrane transport system

Question 1

passive mediated transport is mediated by

Answer 1

ionophores, porins, ion channels, aquaporins, and transport proteins

Question 2

ionophores

Answer 2

may carry ions or form channels

Question 3

porins

Answer 3

provide a passage for ions and non-polar substances

Question 4

ion channels

Answer 4

highly selective and may be gated

Question 5

aquaporins

Answer 5

mediate the transmembrane passage of water molecules

Question 6

transport proteins

Answer 6

may mediate uniport, symport, and antiport transport.

Question 7

ABC transporters move ?

Answer 7

amphipathic substances from one side of the membrane to the other

Question 8

how does secondary active work?

Answer 8

it uses the existing ion gradient to drive unfavorable transport of a second substance

Question 9

how does non-mediated occur

Answer 9

through simple diffusion. This is done also for steroids and oxygen

Question 10

what substances use mediated transport

Answer 10

ionic and polar substances.

Question 11

facilitated diffusion (passive mediated transport) works by

Answer 11

A specific molecule flows from high concentration to low concentration.

Question 12

active transports works by

Answer 12

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.

Question 13

what are the 2 kinds of ionophores

Answer 13

• carrier ionophore

- channel forming ionophore

Question 14

an example of carrier ionophore is

Answer 14

valinomycin. It has 10K more affinity for K than for Na

Question 15

list the 4 types of gating for ion channels

Answer 15

mechanosensitive
ligand gated
signal gated
voltage gated

Question 16

when are gap junctions fully open?

Answer 16

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)

Question 17

GLUT 1 is a

Answer 17

uniport

Question 18

ATP-ADP translocator is a

Answer 18

antiport

Question 19

the alpha chain and the beta chain in Na-K -ATPase function as

Answer 19

• 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.

Question 20

what are cardiac glycosides? And their functions?

Answer 20

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.