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Physiology 1 (WPH) > L/D 1: osmotic pressure - Dr. Head > Flashcards

L/D 1: osmotic pressure - Dr. Head Flashcards

1
Q

define molarity

A

moles / liter

M / L

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2
Q

define osmolarity

A

equivalents / liter

zM / L

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3
Q

what is the osmolarity of 1 molar glucose solution

A

1 M glucose = 1 Osm glucose

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4
Q

what is the osmolarity of 2 mM NaCl

A

2 mM NaCl = 4 mOsm NaCl

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5
Q

what is the osmolarity of 3 mM CaCl2

A

3 mM CaCl2 = 9 mOsm CaCl2

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6
Q

define molality

A

moles / kg

M / kg

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7
Q

define osmolality

A

equivalents / kg

zM / kg

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8
Q

4 things that affect solute movement across membrane

A
  • g (conductance/permiability ~ charge, size, etc)
  • dC (concentration)
  • dV (electric potential of membrane)
  • dP (hydrostatic pressure (rare in physiologic membranes))
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9
Q

T/F osmosis only occurs if there is a degree of impermeability for a solute across the membrane

A

true – if membrane completely permeable, there is no osmosis or osmotic pressure, only simple diffusion

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10
Q

what is the ionic charge of water (z)

A

zero - no net ionic charge of water. therefore water has only chemical potential, no electrical potential

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11
Q

T/F water can have electrochemical potential

A

false - water can only have chemical potential (due to concentration gradient). it cannot have electric potential as it has no net ionic charge (valence is zero)

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12
Q

osmosis is…

A

movement of water from high water concentration to low water concentration

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13
Q

what is a “colligative” property of a solution

A

depends only on number of solute particles per unit volume (not size, molecular weight, or chemical nature of solute particles)

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14
Q

3 examples of colligative properties include:

A

vapor pressure
freezing point
boiling point

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15
Q

how does solute concentration affect freezing point of solution?

A

depresses freezing point (1.86 degrees C per Osm)

more solute, lower temp needed to freeze - more difficult to form crystal lattice

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16
Q

how does solute concentration affect boiling point of solution?

A

elevates boiling point
(more solute, higher temp needed to boil - fewer solvent particles at surface therefore lower vapor pressure more difficult to exceed atmospheric pressure)

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17
Q

how does solute concentration affect vapor pressure of solution?

A

lowers vapor pressure

fewer solvent particles at surface

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18
Q

how does 1 Osm solute concentration affect freezing point

A

1 Osm ~ 1.86 degrees C freezing point depression

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19
Q

how can osmolality of a solution be calculated from freezing point depression?

A

freezing point depression / 1.86 - Osm
-because-
1 Osm ~ 1.86 degrees C freezing point depression

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20
Q

the typical osmolality of most body fluids

A

~ 285 mOsm / kg

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21
Q

what is a rough way to estimate the osmolality of body fluids?

A

serum [Na+] x 2

breaks down with marked elevation of blood glucose or urea or other solutes

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22
Q

T/F there is no known mammalian active transport mechanism for water

A

true

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23
Q

T/F most cell membranes are highly permeable to water

A

true

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24
Q

what is oncotic pressure

A

the part of osmotic pressure attributable to large poorly permeant protein molecules

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25
Q

water is at equilibrium across most cell membranes in the body. name 2 exceptions

A
  • capillary walls (significant gradients of hydrostatic & oncotic pressure)
  • certain regions of renal tubules (active salt transport and low water permeability result in steady state differences in osmotic pressure)
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26
Q

how is osmotic pressure related to osmolality?

A

osmotic pressure is inversely related to osmolality

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27
Q

a hypoosmotic solution refers to

A

lower solute concentration than cell osmolality

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28
Q

a hyperosmotic solution is…

A

higher solute concentration than cell osmolality

29
Q

an isosmotic solution is…

A

equally solute concentration compared to cell osmolality

30
Q

a hyperosmotic solution will cause a cell to __

A

that depends. cell will shrink if hyperosmotic solute is impermeable to membrane, will swell if hyperosmotic solute is permeable to membrane (permeable solutes do not contribute to tonicity)

31
Q

a hypoosmotic solution will cause a cell to __

A

swell. cell will swell if hypoosmotic solute is impermeable to membrane, will also swell if hypoosmotic solute is permeable to membrane

32
Q

hyper, hypo, and iso osmotic distinctions are applicable only to solutes with what kind of characteristics

A

solutes to which the cell membrane are impermeable. permeable solutes = no osmotic pressure because solute will diffuse

33
Q

solutes are osmotically less “effective” if…

A

the membrane is permeable to them

no osmotic pressure because solute will diffuse

34
Q

T/F osmolality is related to osmotic pressure, but tonicity is not

A

false

  • osmolality is just concentration of solutes (permeable or impermeable), a property of a particular solution that is independent of any membrane, and therefore independent of osmotic pressure
  • tonicity accounts for only impermeable solutes, and is a property of a solution in reference to a particular membrane and related to osmotic pressure
35
Q

do osmolality and tonicity account for both permeable solutes and impermable solutes?

A

osmolality - both permeable and impermeable

tonicity - impermeable solutes only

36
Q

what is the difference between hyper/hypo/iso osmolarity vs tonicity?

A
  • osmolality depends on relative solute concentration

- tonicity depends on relative impermeable solute concentration

37
Q

T/F relative osmolarity determines cell swelling vs shrinking

A

false - relative tonicity determines cell swelling vs shrinking

38
Q

T/F relative tonicity determines cell swelling vs shrinking

39
Q

how do you determine relative osmolality vs tonicity?

A
  • relative osmolality - compare osmolalities

- relative tonicity - compare osmolalities of impermeable ions only

40
Q

a hypertonic solution will cause a cell to __

41
Q

a hypotonic solution will cause a cell to __

42
Q

T/F a solution can be hyperosmotic but hypotonic

A

true - with relatively high concentrations of permeable solutes like urea

43
Q

T/F a solution can be hypoosmotic but hypertonic

A

false - a hypoosmotic solution will always be hypotonic because osmolality of impermeable ions will be relatively lower

44
Q

compared to a typical cell, what is the relative osmolality and tonicity of a 0.15 M NaCL and 0.3 M urea solution?

A

hyperosmotic (solute conc is greater)

isotonic (impermeable solute concs are ~same)

45
Q

compared to a typical cell, what is the relative osmolality and tonicity of a 0.3 M urea solution?

A

isosmotic (solute concs are ~same)

hypotonic (impermeable solute conc is less)

46
Q

what is the van’t Hoff relationship

A

d(pi) = RTdC
delta osmotic pressure = RT delta concentration
R = gas constant, T = temp

47
Q

how do you calculate osmotic pressure of an impermeable solute solution?

A

d(pi) = dC RT
delta osmotic pressure = delta concentration x RT
d(pi) = dC RT
R = gas constant, T = temp

48
Q

how can you derive the osmotic pressure equation from the gas law?

A 
PV = nRT
P = (n/V) RT
P = C RT
dP = dC RT
d(pi) = dC RT
49
Q

RT =

A

19,300 mmHG / M

50
Q

how does the van’t Hoff relationship change if the solute is permeable to the membrane?

A

d(pi)eff = rho dC RT

effective osmotic pressure = reflection coefficient x delta concentration x RT

51
Q

how do you calculate osmotic pressure of a permeable solute solution?

A

d(pi)eff = rho dC RT
effective osmotic pressure = reflection coefficient x delta concentration x RT
R = gas constant, T = temp

52
Q

d(pi)eff = rho dC RT

A

effective osmotic pressure = reflection coefficient x delta concentration x RT
R = gas constant, T = temp

53
Q

d(pi) = dC RT

A

osmotic pressure = reflection coefficient x delta concentration x RT
R = gas constant, T = temp
! impermeable solutes only ! otherwise use reflection coefficient to calculate effective osmotic pressure

54
Q

what percentage of body weight is:

  • H2O
  • ICF
  • ECF
  • plasma
  • interstitial fluid
A 
60% H2O
40% ICF
20% ECF
4% plasma
16% interstitial
55
Q

T/F osmotic pressure is equivalent to the hydrostatic pressure required to oppose osmosis

56
Q

what is the osmotic pressure of water?

A

zero

osmotic pressure ~ osmolality of nonpermeant solutes

57
Q

how does osmotic pressure relate to osmolality?

A

directly related
high osmolality = high osmotic pressure
low osmolality = low osmotic pressure

58
Q

T/F water flows from high to low osmotic pressure

A

false - water flows from low to high osmotic pressure (osmotic pressure ~ osmolality of permeant solutes)

59
Q

hemolysis

A

rupturing of erythrocytes

60
Q

rupturing of erythrocytes is called __

61
Q

compared to a typical cell, what is the relative osmolality and tonicity of a 0.15 M NH4Cl solution?

A
  • isosmotic - solute concs are ~same
  • hypotonic - neither NH4+ or Cl- are permeable, but NH4+ exists in equilibrium with a small amount of NH3, which is permeable and enters the cell, turns back into NH4+, and draws more NH3 into cell. The result is a build up of osmotically active particles (NH4+) in the cell that causes influx of water and eventual hemolysis
62
Q

“crenation” signifies…

A

“scalloped” or “notched” edges, e.g. an erythrocyte in a hypertonic solution

63
Q

a crenated erythrocyte is…

A

shrunk, as in a hypertonic solution

64
Q

T/F the effective osmotic pressure is the sum of the contribution from the different solutes

A

true

pi effective = rho1pi1 + rho2pi2 + …

65
Q

how do you calculate the effective osmotic pressure when multiple solutes of varying permeabilities are present in solution?

A

pi effective = rho1pi1 + rho2pi2 + rho3pi3 + …

the effective osmotic pressure is the sum of the contribution from the different solutes

66
Q

the reflection coefficient for a completely permeant solute will be

67
Q

the reflection coefficient for a completely impermeant solute will be

68
Q

in terms of golf balls, tennis balls, and soccer balls chucked at a wire fence, what might be the respective reflection coefficients of the balls?

A 
golf = 0
tennis = 0.5
soccer = 1
69
Q

T/F in a U tube with a semipermeable membrane separating 2 solutions with different impermeant solute concentrations, there is no net flow when osmotic pressure = hydrostatic pressure

A

false - there is no net flow when osmotic pressure = the DIFFERENCE in hydrostatic pressure

Physiology 1 (WPH) (18 decks)

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