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Cell physiology and pharmacology > Lecture 4- Principles of solute and water movement > Flashcards

Lecture 4- Principles of solute and water movement Flashcards

1
Q

in a 70kg man how much of him is water

A

60% of 70kg= 42L

men are 60% water- Kg=L

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2
Q

how much of total water volume in humans is intracellular

A

2/3

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3
Q

how much of total water volume in humans is extracellular

A

1/3

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4
Q

extracellular spaces are also called

A

interstitial

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5
Q

therefore in a 60kg man with 42 L of water, how much is intracellular

A

28L

2/3 of 42

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6
Q

therefore in a 60kg man with 42 L of water, how much is extracellular

A

14L

1/3 of 42

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7
Q

E.g. if someone’s put on 1.5kg and has oedema they will have increased how much fluid in ECF

A
  • 1.5kg=1500ml

* 1/3 of 1500 = 500 ml

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8
Q

what counts as intracellular fluid

A

within cvcells

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9
Q

what counts as extracellular fluid

A
  • interstitial
  • plasma
  • lymph
  • trancellular fluid
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10
Q

ionic concnetrations within ECF

A
  • High [sodium]
  • Low [potassium]
  • High [chloride]
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11
Q

ionic concentrations within the ICF

A
  • Low [ sodium]

- high [potassium]

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12
Q

osmolarity of of the ECF

A

between 285-310 mOsm

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13
Q

osmolarity of ICF

A

290mOsm

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14
Q

osmolarity of ICF and ECF should be

A

equalise- prevent water flooding into he cell- ions in equilibrium

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15
Q

phospholipid membrane permeable to

A

uncharged and non polar molecules, small hydrophobic molecules e.g. ammonia and water

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16
Q

cell membrane lets what in

A

CHO, sugars, proteins amino acids lipids, salts, O2 and water into the cell

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17
Q

cell membrane lets what out

A

lets Water, ammonia. Salts, CO2 out

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18
Q

what maintains cholesterol fluidity

A

cholesterol

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19
Q

what can slip through the membrane

A

lipid soluble molecules e.g. fats and lips

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20
Q

large hydrophobic molecules

A

struggle to pass the membrane

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21
Q

what sort of molecule can pass the membrane

A
  • Small uncharged non-polar
  • Small hydrophobic molecules can get through e.g. gases
  • Urea can easily diffuse through membrane (accept in kidneys)
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22
Q

what sort of molecule cannot pass the membrane

A
  • Large uncharged molecules e.g. glucose cannot just pass through the membrane
  • Large charged molecules cannot pass through (e.g. ATP, amino acids)
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23
Q

cell membrane example of permeability

A
  • permeable to urea and water.

- not permeable to ions

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24
Q

capillary example of permeability

A

Permeable to urea, water,Na or K (fenestrations). Not permeable to plasma proteins

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25
Q

types of movement between compartments

A

passive transport

active transport

vesicular transport

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26
Q

passive transport

A
  • No energy needed- diffusion
  • Movement down concentration gradient
  • E.g. Facilitated diffusion (water through an aquaporins)
  • E.g.Osmotic, oncotic and hydrostastic
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27
Q

active transport

A
  • Uses ATP

* Movement against conc gradient

28
Q

vesicular transport

A
  • Pinocytosis (cell drinking)
  • Phagocytosis
  • Form of active transport
  • Not using channels
29
Q

diffusion

A

Solute movement across a lipid bilayer through entry into the lipid phase occurs by simple diffusion- movement occurs downhill and is passive

30
Q

diffusion is irrespective of

A

other substances

31
Q

flux describes

A

• ‘Flux’ describes how molecules move expressed in moles/cm2/second

32
Q

when there is no movement

A

flux is 0

33
Q

movement of change is proportional to

A

gradient of conc difference

34
Q

if membrane is thicker

A

flux will be slower e..g single cell wall of alveolus

35
Q

diffusion of 2 solute

A

Concentration gradient of different substances are independent of each other

36
Q

facilitated diffusion e.g. aquporins

A

Move from, high to low concentration through a protein channel
• Protein molecules spans the membrane
• Permeable to the movement of that substance (specific)
• No energy needed
• Facilitated= with help
• E.g. aquaporins

37
Q

gated channels

A

Proteins that open only in presence of stimulus (signal)

  • Stimulus different from transported molecules
  • E.g. ion-gated
  • E.g. voltage gated
38
Q

active transport

A

Cells need molecules to moleucles against concentration gradients

  • Need protein pump
  • Requires ATP
    e. g. Na/K+ ATPase pump
39
Q

large molecules are transported bvia

A

vesicular transport- requires ATP

40
Q

two main types of vesicular transport

A

1) exocytosis

2) endocytosis

41
Q

exocytosis

A

out of cell

42
Q

types of endocytosis

A

1) phagocytosis
2) pinocytosis
3) receptor mediated endocytosis

43
Q

phagocytosis

A

cellular eating

44
Q

pinocytosis

A

cellular drinking

45
Q

constitutive secretion

A

is the default pathway and is used primarily to replenish material at the plasma membrane and certain membrane-bound organelles.

46
Q

regulated secretion

A

Regulated secretion terminates in secretory vesicles that store secreted material until a signal triggers fusion with the plasma membrane.

–> triggered by Ca2+!!!!!!!!!

47
Q

water moves across the membrane relatively

A

slowly

48
Q

aquaporins

A

allow water to move across the plasma membrane very quickly

49
Q

if the solution becomes hypotonic

A

then water will move across membrane by osmosis an enter the cell and the cells will swell and burst

50
Q

if the solution is isotonic

A

same osmolarity either side of the membrane) water molecules will enter and exit the cell in equilibrium- as many will enter as will leave

51
Q

in hypetonic solutions the cell will

A

shrinking because the water would move across the membrane into the ECF

52
Q

water will move until

A

osmotic forces on either side of the membrane is equal

53
Q

Osmole is the measure of

A

solutions ability to create osmotic pressure and move water

- Proportional to the number of osmotic particles formed in solution

54
Q

In normal conditions osmolality of plasma is

A

equal to interstitial fluid = intracellular fluid = 280-210 mOsm/kg

55
Q

clinically how is osmalility determined

A 
by ECF (Na+ and Cl- =80%)
-	Serum osmolality can be estimated by doubling serum sodium
56
Q

hyperotnic

A

more solute, less water

57
Q

hypertonicity

A

hypertonic solution will loose water, shrivel and lyse

58
Q

hypotonic

A

less solute, more water

59
Q

hypotonicity

A

hypotonic solution will gain water, swirl and cytosolyse

60
Q

isotonic

A

equal solute, equal water- no movement of water

61
Q

aquaporins work through

A

facilitated diffusion

62
Q

how much quicker can water diffuse across the membrane using aquaproins

A

200x quicker

63
Q

structure of aquaporins

A
  • Made up of 5 subunits - tetrameric
  • 6 transmembrane alpha helix protein
  • Inner cavity narrow and lined withy hydrophilic AA
  • At the centre (+) residues
  • Prevents movement of charged ions e.g. protons
  • Aquaporins don’t disrupt H+ ion gradient in ATP production
64
Q

what does aquaporins let through

A

just water- occasionally urea

65
Q

how many isoforms of aquaporins

A

10

66
Q

how does water move through aquaporins

A

Water molecules line up one behind the other and pass single file through the hydrophilic channel
 1000,000 molecules/ min

67
Q

why is movement through aquaporins movement still osmosis

A

 Movement still depends on solute concentration gradient

 Still osmosis

Cell physiology and pharmacology (20 decks)

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