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Human Physiology Block 1 > Membrane Transporters in Action > Flashcards

Membrane Transporters in Action Flashcards

1
Q

do RBCs have high or low permeabilit?

A

low

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2
Q

respiration/RBC tranport

A

anion exchanger

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3
Q

each individual transporter can exchange anions (which ones?) across the RBC membrane at rates that reach ( )

A
  • Cl and HCO3

- 100,000 times per sec

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4
Q

what is the drivers for anion exchangers

A

CO2

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5
Q

anion exhanger: to be transported effectively in blood, CO2 must be converted to the musch more soluable ( )

A

HCO3

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6
Q

anion exchanger: the enzyme that catalyzes this process

A

carbonic anhydrase

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7
Q

anion exchanger: what is very membrane permeable, diffuses out of celss, into plasma, and then into RBCs

A

CO2

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8
Q

anion exhcanger: In RBCs, CO2 reacts with water to form ( )

A

one proton and one HCO3 anion

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9
Q

anion exchanger: the HCO3 anion is exchanged for a ( ) and the HCO3 anion in carried in plasms to ( )

A
  • chloride anion

- lungs

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10
Q

anion exchanger: as RBCs pass the lungs, what happens?

A

the entire reaction path functions in reverse to move CO2 out of the RBCs and into the alveoli of the lungs

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11
Q

( )% of all cytoplasmic chloride ions in RBCs exchange across the plasmalemma in less that 50 ms

A

50%

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12
Q

anions: all reactions are completely reversible so they can run in reverse as dictated by the ( ) in theperipheral ciriculation vs. the lungs

A

CO2 gradients

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13
Q

epithelial cells are physically connected to each other via

A

tight junctions

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14
Q

tight junctions: do not allow passage of ( ), and ( ) do not pass through them easily, their permeability to ( ) is limitied

A
  • proteins
  • small solutes
  • ions
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15
Q

often, tight junctions allow passage of ( ) while being relatively impermeable to ( )

A
  • cations

- anions

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16
Q

in some cases, tight junctions may be more impermeable to ( ) and in a few cases they are known to be more permeable to ( )

A
  • ions

- anions than cations

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17
Q

to accomplish transport across a cell layer, it is essential that cells are ( )

A

polarized (basolateral side and apical side)

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18
Q

in the majority of epithelia, the Na/K pump is localized to what side of the cell membrane?

A

basolateral

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19
Q

provides the initial driving force

A

Na/K pumps

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20
Q

whenever solutes or ions move across a membrane or epithelium in one direction, water will tend to follow across in the same direction and therefore ( )

A

minimize osmotic gradients

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21
Q

in an isoosmotic solutions, there are about how many molecules of water for each dissolved particle?

A

185 molecules

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22
Q

most physiological secretions are ( )

A

hypotonic

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23
Q

what is maintained?

A

electric neutrality (ex. Na will promote Cl movement and vice versa)

24
Q

the body attempts to absorb all nutrients from the gut, and to do so the body uses ( )

A

both cotransporters and uniporters

25
Q

glucose is absorbed from the gut by ( )

A

enterocytes

26
Q

it is critical for digestive function that these gut secretions have a high ( ) content

A

NaCl

27
Q

Since the Na concentration of the gut is high, Na/glucose transporters are used to move Na and glucose together into ( ), whereby all glucose in the gut can be absorbed

A

enterocytes

28
Q

On the opposite side of the enterocyte, simple glucose uniporters called ( ) are used to move glucose into the interstitial space

A

GLUT

29
Q

driving force in absoption of glucose in kidney

A

glucose gradient between the cytoplasm and interstitial space

30
Q

a hypotonic secretion is produced in two overall steps:

A

1) salt is secreted and water follows salt to generate a primary isotonic secretion
2) salt is reabsorbed to generate the final hypotonic secretion

31
Q

in the case of sweat gland, ( ) is secreted into the secretory tubule and water follows the movement of salt to generate an isotonic fluid

A

NaCl

32
Q

salt is reabsorbed as fluid moves through the ducts of the sweat gland, so that the final sweat is ( )

A

hypotonic

33
Q

secretory tubule contains a high density of water channels which is necessary to favor the movement of ( )

A

water into the tubule

34
Q

why do cells in the duct contain very few water channels?

A

so water movement out of the duct is minimized during salt reabsorption

35
Q

during the secretion of the primary sweat, the energy of the ( ) is used to pump Cl across both membranes into the tubule

A

Na and K

36
Q

sweat: Na, K, and Cl are transported across the basolateral membrane via ( ), driven mostly by the ( ) gradient into the cell

A

Na, K,Cl cotransporters; Na

37
Q

sweat: ( ) ions that enter across the basolateral side via pumps and transporters cycle back across the basolateral side via ( ), generating membrane potential across the basolateral side

A

K; K channels

38
Q

sweat: ( ) ions that enter via cotransporters cycle back across the basolateral membrane by being pumped out by ( )

A

Na; Na/K pumps

39
Q

sweat: ( ) leaves cells on the apical side via ( )

A

Cl; Cl channels

40
Q

Since Cl is negatively charged, its movement across the apical membrane generates an ( ); what is this called?

A

electrical field across the entire cell; transcellular potential

41
Q

sweat: it is critical that the tight junctions allow ( ) to move between cells, but not ( )

A
  • cations

- anions

42
Q

sweat: the negative electrical field on the apical side attracts Na ions to pass through the tight junctions into the lumen. What is now established?

A

a flux of NaCl all the way across the epithelium

43
Q

sweat: this movement of NaCl generates an osmotic gradient, osmolatiy being higher in the ( ) than on the ( ), water therefore moves through water channels across the cell

A
  • lumen

- basolateral

44
Q

sweat: secretion of NaCl and water depends on the coordinated function of ( )

A

Na/K pumps, Na/K/Cl co-transporters, K channels, and Cl channels

45
Q

as sweat passes through the duct of the sweat gland, what heppens?

A

ions are reabsorbed

46
Q

sweat: to avoid that water is reabsorbed with ions, what is important?

A

that these epithelial cells do NOT have water channels

47
Q

both apical and basolateral membranes of these cells contain ( )

A

CFTR Cl channels

48
Q

basolateral: K cycles back out of the cells through ( ), therefore making a large inside negative membrane potential across the membrane

A

basolateral K channels

49
Q

basolateral: this negative potential is used to drive ( ) out across the basolateral side through CFTR Cl channels, therefor making ( ) low

A

Cl; cytoplasmic Cl

50
Q

apical: contains both ( ) channels

A

CFTR Cl channels and Na channels

51
Q

apical: ( ) enter the cell from the duct lumen through these channels, diffusing down their concentration gradients

A

Na and Cl

52
Q

apical: the currents generated by ( ) influx tend to cancel each other out so there is very little membrane potential across the apical membrane side

A

Na and Cl

53
Q

what are the Na channels that are used for epithelia that are highly selective for Na but are very different from voltage gated Na channels used to make APs?

A

Epithelial Na Channels (ENAC)

54
Q

why can’t CFTR can’t reabsorb ion?

A

because Cl channels are not there

55
Q

Why is sweat salty when CFTR channels are lost?

A

because NaCl is not effectively reabsorbed

Human Physiology Block 1 (15 decks)

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