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Thanh Cell Physiology Unit III > Epithelial Transport > Flashcards

Epithelial Transport Flashcards

1
Q

Na/K channels are located on apical/basolateral membrane.

A

Basolateral side

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2
Q

give some examples of where tight epithelia are located

A
  1. sweat glands

2. distal parts of kidney tubules

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3
Q

apical synonyms

A

mucosal

lumenal

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4
Q

basolateral

A

serosal

peritubular

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5
Q

Majority of epithelia are leaky/tight

A

leaky: massive transport of substances

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6
Q

Functions of epithelia

A
  1. absorption of salt
  2. secretion of fluid
  3. turning on Cl- channel
  4. absorption of nurtrients
  5. regulation
  6. transport of water
  7. ridding body of metabolic waste
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7
Q

List Some Different areas in the body that contain epithelial cells

A 
Gi tract, 
Kidneys,
exocrine glands
gall bladder
choroid plexus
ciliary body
corneal epithelium
mucous membranes
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8
Q

Is the lung lined with epithelium or endothelium?

A

endothelium

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9
Q

The apical surfaces faces what? What does the apical surface contain that gives the epithelium its special function?

A

the ‘special fluid’ or lumen side

  • contains special transporters
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10
Q

In epithelial cells where tight junctions are leaky, what pathway is provided and what is its function?

A

peracellular shunt pathway: allows movement of water and solutes

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11
Q

Some examples of leaky tight junctions

A

proximal part of kidney
gallbladder
small and large intestines

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12
Q

two routes to cross epithelium

A
  1. can cross both membranes by entering one and exiting other (apical or basal visa versa)
  2. not cross membranes but instead pass through pericellular shunt
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13
Q

Na/K pump is the driving force for transport of what? (give some examples)

A

nearly all transport: water, salts, nutrients, non volatile metabolic wastes

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14
Q

Are protons dependent on Na/K pumps?

A

No - protons rely on primary active transport

- ie: stomach and kidneys

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15
Q

The apical/basolateral membrane is highly permeable to K and contain low Na permeability?

A

Basolateral (like most cells)

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16
Q

What is the value of the membrane potential of the basolateral membrane? Apical membrane?

A

basolateral: Vm = -70mV
apical: Vm = ~+10mV

17
Q

The apical/basolateral membrane is highly permeable to Na and contain low K permeability?

A

apical

18
Q

How is salt and water transported from the apical to basolateral solution?

A
  1. sodium leak thru apical membrane (down [ ] gradient]
  2. sodium pumped back out thru basolateral side via Na/K pump
  3. Cl passively follows (bc its attracted to positive ch)
  4. water is 3rd wheel and follows.
19
Q

If the Na/K pump was blocked,, what would happen to water flow?

A

decrease

  • with pump closed, Na entry reduced, Cl entry reduced, water entry reduced.
20
Q

The apical solution is positive/negative with respect with basolateral solution

A

negative

(Na+ leaks thru apical, pumped thru basolateral side,
apical side becomes more negative)

21
Q

transepithelial potential difference measures what?

A

Difference between

Vm (basolateral) - Vm (apical)

22
Q

What is an electroneutral cotransporter?

A

A transporter that transports equal charges of ions across the membrane.

-ie: 1 K, 2 Cl-, 1 Na

23
Q

in normal resting cells, the Cl- channel is open/closed

A

closed

24
Q

main defect in cholera and cystic fibrosis?

A

Defect in Cl- channel in apical membrane (In Gi tract and lung)
-causes channel to be overly activated –> secretes electrolyte into lumen –> water follows (DIARRHHEEAA)

25
Q

These channels/pumps are located on the apical/basolateral membrane

  1. Na/K pump
  2. Cl- channel .
  3. K+ channel
  4. Na/K/Cl cotransporter (pump)
A
  1. basolateral
  2. apical
  3. basolateral
  4. basolateral
26
Q

compare paracellular and intercellular shunt pathways

A

Apical Basolateral
_________________________

Na leaks ———————–>
Cl follows via paracellular SP

<———————— Cl- leaks
Na follows via intercellular shunt pathway

27
Q

Describe how nutrients are absorbed

A

amino acids/sugars are pumped from the GI lumen into the blood by GI epithelium.

then passively diffuses out of the cell into interstitial fluid

28
Q

What types of transport are sugar and amino acid pumps?

A

secondary active transport

this means that if Na is removed, pumps stop working

29
Q

Describe differences of glucose transport across epithelial and non epithelial membranes

A

epithelial apical membrane:
- secondary AT

everything else:
- facilitation Diffusion
(plasma membrane of non epithelial cells + basolateral membrane)

30
Q

absorbed/not absorbed in GI?

  1. L-amino acids
  2. L-sugars
  3. D-amino acids
  4. D- sugars
A
  1. Absorbed
  2. Not absorbed
  3. not absorbed
  4. absorbed
31
Q

rise/reduction in plasma osmolarity will cause you to be thirsty

A

rise

  • severe dehydration occurs when plasma osmolarity is raised by less than 10%
32
Q

What is the most important function of the kidney!!??

A

getting rid of non volatile metabolic waste products. (urea and protons)

(cant be expelled by lungs like volatile CO2)

33
Q

Uremia

A

urine in the blood

34
Q

Instead of a urea transporter (none exists), what does the kidney have?

A

an ULTRAfiltrate. duh

  • requires lots of ATP
  • regulates ECF composition
35
Q

How does the kidney regulate water?

A

kidney tubule lumen reabsorbs solutes.

epithelium is made water impermeable (cannot follow solutes) and gets pissed out

36
Q

What makes the epithelium impermeable to water?

A

the hypothalamus senses too much water/drop in plasma osmolarity
- stops secreting ADH (vasopressin) and causes epithelial cells to remove aquaporins from their apical membrane

37
Q

4 important substances that are never pumped across the membrane

A

water
O2
CO2
Urea

38
Q

Explain CBIGK and functions of each

A

treatment of hyperkalemia

  • Calcium: quiets cells
  • Bicarb: start reuptake of K
  • Insulin + Glucose: Juices/fires up Na/K pump
  • kayexalate: get K out of body

Thanh Cell Physiology Unit III (26 decks)

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