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Physiology 1 (WPH) > L2: solute & water transport - Garcia-Diaz > Flashcards

L2: solute & water transport - Garcia-Diaz Flashcards

1
Q

this type of transporter contains a conducting pore that can be accessed by ions from either side of the membrane simultaneously

A

channel protein

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2
Q

what determines the selectivity of a channel protein?

A

charge and structural features of amino acids lining the pore

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3
Q

4 kinds of channel gates include

A
  • voltage-gated channels
  • ligand-operated channels
  • stretch-activated channels
  • leak channels
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4
Q

what is the force driving molecules through a channel?

A

electrochemical potential - always downhill

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5
Q

what kind of transport protein is involved in “facilitated diffusion” ?

A

carrier protein

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6
Q

what is the force driving net solute flux in carrier protein transport?

A

electrochemical potential - always downhill

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7
Q

is rate of transport higher for channel protein or carrier protein?

A

channel protien – carrier protein must change conformation

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8
Q

translocation across carrier proteins involves 3 steps:

A
  • binding
  • conformation change
  • release
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9
Q

T/F the relationship between flux across a carrier protein and substrate concentration is linear

A

false - hyperbolic

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10
Q

what are 3 properties that determine the flux vs substrate concentration curve for a carrier protein

A
  • saturation
  • affinity
  • competition
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11
Q

transport is considered ___ if it cannot move solutes from low to high electrochemical potential

A

passive

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12
Q

a P-class ATPase…

A

couples hydrolysis of ATP with phosphorylation/dephosphorylation of itself and active transport of a substrate

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13
Q

Na+ K+ ATPase

A

K+K+ in
Na+Na+Na+ out
contributes to membrane potential and cell volume maintenence

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14
Q

2 kinds of Ca2+ ATPases

A

keep cytosolic [Ca2+] low:

  • PMCA (plasma membrane calcium pump) transports Ca2+ out & H+ in across plasma membrane
  • SERCA (smooth endoplasmic reticulum calcium pump) transports Ca2+Ca2+ in & H+H+ out across endoplasmic reticulum membrane
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15
Q

H+ ATPase

A

maintains cell PH by secreting protons

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16
Q

H+ K+ ATPase

A

responsible for gastric acid secretion

-H+ out for K+ in

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17
Q

ABC transporter stand for

A

ATP binding casette transporter

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18
Q

3 examples of P=class ATPases

A
  • Na+ K+ ATPase
  • Ca2+ ATPases
  • H+ ATPase
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19
Q

MDR1

A

multidrug resistant transport protein

  • extrudes anticancer drugs from cells and makes cells resistant to these drugs
  • an ABC transporter that uses ATP hydrolysis to fuel active transport
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20
Q

how do ABC transporter proteins utilize ATP

A
  • some use energy from ATP hydrolysis for active transport

- some use ATP binding to regulate function

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21
Q

describe the structure of ABC transport proteins

A
  • two nucleotide binding domains
  • two transmembrane domains
  • each transmembrane domain typically has 6 membrane spanning segments
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22
Q

___ is an example of an ABC transporter that uses ATP hydrolysis to fuel active transport

A

MDR1
multidrug resistant transport protein
-extrudes anticancer drugs from cells and makes cells resistant to these drugs

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23
Q

___ is an example of an ABC transporter that uses ATP binding to regulate transport

A

CFTR
cystic fibrosis transmembrane regulator
- Cl- channel that opens on ATP binding. localized in many secretory epithelia (pancreas, lungs, intestines, sweat glands)

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24
Q

CFTR

A

cystic fibrosis transmembrane regulator

  • an ABC transporter that uses ATP binding to regulate function
  • Cl- channel that opens on ATP binding. localized in many secretory epithelia (pancreas, lungs, intestines, sweat glands). Hereditary mutation causes cystic fibrosis disease - characterized by deficient pancreatic and airway secretions
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25
Q

human ABC transporters are classified into seven distinct subfamilies of proteins named ABCA through ___

A

ABCG

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26
Q

these 2 types of transport proteins are not directly linked to the cell’s metabolic energy, but are able to move one solute uphill using energy released from the downhill movement of another solute

A
  • cotransporter (symport)

- exchanger (antiport)

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27
Q

Na+ dependent glucose transporter is an example of what kind of transport protein?

A

a cotransporter (symport)

28
Q

what do you call the kind of transport performed by cotransporters and exchangers?

A

secondary active transport – can perform uphill transport of one substrate but depends on downhill gradient of another substrate, which is often maintained by another proteins active transport (eg Na K ATPase)

29
Q

what is secondary active transport

A

can perform uphill transport of one substrate but depends on downhill gradient of another substrate, which is often maintained by another proteins active transport (eg Na K ATPase)

30
Q

what is primary active transport

A

transport up-gradient directly linked to cell’s metabolic energy (ATP hydrolysis)

31
Q

what are 2 types of primary active transporters?

A

pumps (ATPases) and ABC transporters

32
Q

what are 2 types of passive transporters?

A

channels and carriers

33
Q

what are 2 types of secondary active transporters?

A
  • cotransporters (symports)

- exchangers (antiports)

34
Q

T/F a solution with high osmolality has a high concentration of water

A

false - high osmolality is high solute concentration and therefore lower water concentration

35
Q

osmotic pressure =

across solute impermeable membrane

A

pi = RTCs

osmotic pressure = gas k x temp x concentration

36
Q

T/F water moves from high osmotic pressure to low osmotic pressure

A

false - water moves from low osmotic pressure (pure water) to high osmotic pressure (high solute concentration)

37
Q

van’t Hoff expression

A

pi = RTCs

osmotic pressure = gas k x temp x concentration

38
Q

effective osmotic pressure =

across solute semi-permeable membrane

A

pi effective = rhoRTCs

rho = reflection coefficient 0<1

39
Q

a reflection coefficient represents

A

fraction of solute molecules colliding with the membrane that are reflected (do not cross it)
0<1

40
Q

how is reflection coefficient related to permeability

A

inversely proportional

41
Q

name one place that the reflection coefficient in a capillary is very low

A

discontinuous capillaries in the liver

42
Q

name one place that the reflection coefficient in a capillary is very high

A

tight continuous capillaries in the brain

43
Q

what two types of water pressure drive net water flow

A

hydrostatic

osmotic

44
Q

oncotic pressure

A

osmotic pressure due to protiens

45
Q

osmotic due to proteins is called…

A

oncotic pressure

46
Q

Jv = Lp (dP - rhopi)

A

net water flow = membrane hydraulic permeability x (delta hydrostatic pressure - effective osmotic pressure)

47
Q

net water flow is dependent on what two kinds of water pressures

A

hydrostatic pressure - osmotic pressure

48
Q

solute flux across a membrane is related to both ___ and ___

A
  • diffusive flux (permeability x delta concentration)
  • solute dragged by solvent flow [(1-rho) Cs Jv]
  • -(1-reflection x solute conc x net water flux)
49
Q

Js = Ps dCs + (1 - rho) Cs Jv

A

solute flux = (permeability x concentration difference) + (1-reflection x solute conc x net water flux)
= diffusive flux + solvent drag

50
Q

why are most cell membranes highly permeable to water

A

AQPs - aquaporins, water channels

51
Q

tetrameric transport channels of four identical subunits with high selectivity for water are called

A

AQPs

aquaporins

52
Q

an AQP is..

A

an aquaporin - a tetrameric transport channel of four identical subunits with high selectivity for water – gives cell membrane high permeability to water

53
Q

layers of cells usually found lining the luminal surface of hollow organs are called

54
Q

these junctions bind epithelial cells together at the luminal border

A

tight junctions

55
Q

tight junctions are made out of these proteins

A

claudins and occludins

56
Q

net epithelial transport from lumen to tissues is called

A

absorption

57
Q

net epithelial transport from tissues to lumen is called

58
Q

paracellular means

A

between cells

59
Q

describe the “standing osmotic gradient hypothesis,” which explains the absorption of water by epithelia in the absence of osmotic or hydrostatic pressure differences between luminal and interstitial fluids

A

epithelial cells pump Na+ into intercellular spaces, and Cl- follows to create a a small increase in osmolality (3-4 mOsm), which is sufficient to draw a large osmotic flow from the lumen due to the high water permeability of the cell membranes and tight junctions. resultant hydrostatic pressure drives water into into surrounding interstitium. water does not flow in reverse from surrounding interstitium into intercellular epithelial spaces because the reflection coefficient is near zero (so effective osmotic pressure is also near zero)

60
Q

PMCA ATPase

A
  • PMCA (plasma membrane calcium pump) transports Ca2+ out & H+ in across plasma membrane
  • keeps cytosolic [Ca2+] low
61
Q

SERCA ATPase

A
  • SERCA (smooth endoplasmic reticulum calcium pump) transports Ca2+Ca2+ in & H+H+ out across endoplasmic reticulum membrane
  • keeps cytosolic [Ca2+] low
62
Q

this ATPase transports Ca2+ out & H+ in across plasma membrane

A

PMCA (plasma membrane calcium pump)

- transports Ca2+Ca2+ in & H+H+ out across endoplasmic reticulum membrane

63
Q

this ATPase transports Ca2+Ca2+ in & H+H+ out across endoplasmic reticulum membrane

A

SERCA (smooth endoplasmic reticulum calcium pump)

64
Q

GLUT2 transporter

A

transmembrane carrier protein that enables passive glucose transport across membranes

65
Q 
Which of the following mechanisms is an example of secondary active transport?
A.	The calcium ATPase
B.	The GLUT2 transporter.
C.	The epithelial sodium channel.
D.	The sodium-calcium exchange.
E.	The H-pump.
A

D. The sodium-calcium exchange.
(secondary active transport - possible in cotransporters and exchangers - moves one substrate up-gradient by coupling its transport with the energy of the down-gradient movement of another substrate. such transport depends on the concentration gradient of substrate two caused by a separate primary active transport mechanism (e.g. an ATPase pump), therefore this mechanism is considered secondary active transport

66
Q

what transport protein is responsible for gastric acid secretion?

A

H+ K+ ATPase

H+ out for K+ in

Physiology 1 (WPH) (18 decks)

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