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physiology lab exam > lab 2 > Flashcards

lab 2 Flashcards

1
Q

what is diffusion?

A

the movement of molecules from regions of high concentration to regions of lower concentration as the result of random molecular drift. it also includes the passive movement down an electrochemoical gradient in single phased systems, as well as to passive trasnfer across membranes that does not involve specific mechansims

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2
Q

what is the major way that solvent and solutes move across a capillary wall and across cell membanes?

A

diffusion

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3
Q

what is fick’s first law of diffusion?

A

the rate of transport is equal to the diffusion coefficient times the concentration difference over distance

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4
Q

what is osmosis?

A

the movement of water from a less concentrated solution when a semipermeable membrane separates the solutions and when the membrane is impermeable to solute

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5
Q

what are two ways to measure the concentration of particles in a solution of interest?

A
  1. if you have a stable strong and truly semipermeable membrane you can measure hydrostatic pressure, which opposes the movement of water by osmosis
  2. look at colligative properties
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6
Q

what is a colligative property?

A

a property that depends on the number of particles

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7
Q

what is osmotic concentration?

A

the effective concentration of particles in solution

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8
Q

what is osmolality?

A

the osmotic coefficient * number of particles which the molecule forms in solution*number of moles/kg of solvent

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9
Q

what is osmolarity?

A

the osmotic coefficient * number of particles which the molecule forms in solution*number of moles/L of solvent

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10
Q

what does the osmotic coefficient depend upon?

A

the interaction of particles

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11
Q

what is osmotic pressure?

A

the force that tends to move water in an osmotic system

osmotic pressure=RT (Concentration inside-concentration outside)

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12
Q

why are erythrocytes considered osmometers?

A

their membranes are freely permeable
when placed in solutions with an osmotic pressure difference they distort; because they are biconcave disk, they can increase in volume without having to increase their surface area

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13
Q

what are examples of ways to measure osmolality (osmometers)

A

membrane osmometers
measurement of alterations in vapour pressure
measurements of alterations in freezing point

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14
Q

how does a membrane osmometer work?

A

it measures the osmotic pressure with reference to a macromolecular species

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15
Q

how does alterations in vapour pressure measure osmolality?

A

it measures the total effective particle concentration (macromolecules and crystalloid)

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16
Q

how does measuring freezing point measure osmolality?

A

it measures the total effective particle concentration (macromolecules and crystalloid)

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17
Q

what determines the rate of membrane penetration by a solute?

A

the sphere of hydration
the nature of the charge
the molecular size
the lipid solubility

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18
Q

how does lipid solubility alter rate of membrane penetration?

A

increased lipid solubility increases the speed with which they cross the membrane

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19
Q

how does molecular size alter the rate of membrane penetration by the solute?

A

with lipid soluble compounds, increased size means decreased speed of penetration of the membrane. at >200, permeability is considered negligible

20
Q

how does the nature of the charge affect the rate of membrane penetration by a solute?

A

charged molecules are insoluble in lipids. they do not cross membranes

21
Q

how does the sphere of hydration affect rate of membrane penetration by a solute

A

charged particles must shed their hydration shell to cross the membrane, even with transport mechanisms
the larger the hydration shell the slower the transport

22
Q

what is a hydration shell?

A

charged particles are surrounded by a shell of water molecules that is unique for each element

23
Q

with organic acids, when are they more likely to cross a membrane?

A

when they are uncharged. the charged and uncharged species exist in equilibrium. as the uncharged molecules cross the membrane, the equilibrium will reestablish itself on both sides

24
Q

will higher or lower concentrations of solute cause higher rates of diffusion?

A

higher

25
Q

what happens to the red blood cells (and PCV) when they are placed in a solution of <300mOsm?

A

they swell and the PCV increases

26
Q

what is facilitated transport?

A

the movement of molecules across a cell membrane by a protein transporter without the use of energy

27
Q

how can facilitated transport be distinguished from simple diffusion?

A

faciliated transport is

  1. saturable
  2. sensitive to inhibitors of protein-mediated transport
28
Q

can a molecule move against its electrochemical gradient with facilitated transport?

A

no

29
Q

what is the major determinant of diffusion rate?

A

concentration

30
Q

how else can % be expressed?

A

g/100mL

31
Q

how do you convert % to molarity?

A

%=g/100mL1000mL/1Lmol/g=mol/L

32
Q

how do you convert molarity to osmolarity?

A

multiply by the number of osmotically active particles

33
Q

how do you convert molarity to the equivalents/L?

A

multiply the molarity by the total valence

34
Q

how is hemolysis determined?

A

it is determined by holding the tube in front of a well lighted printed page. hemolysis has occurred when the print is clearly visible through the tube as the broken erythrocytes no longer disperse light

35
Q

does water lyse an RBC?

A

yes

36
Q

does 0.3 OsM NaCl lyse the cell?

describe it -motic, -tonic

A

no because the cell is effectively impermeable to these ions because they get pumped out
isoosmotic, isotonic

37
Q

does 0.3 OsM urea lyse the cell?

describe it -motic, -tonic

A

yes because the membrane is permeable to urea.

isoosmotic, hypotonic

38
Q

does 0.3 OsM NH4Cl lyse the cell?

describe it -motic, -tonic

A

It lyses the cell slowly. at first the NH4 is outside the cell but it is in equilibrium with NH3, which enters the cell.
isoosmotic and hypotonic

39
Q

what does it mean to be isoosomotic?

A

the fluids have the same osmotic particle concentratino

40
Q

what does it mean to be isotonic?

A

the fluids have the same impermeable particle concentration

41
Q

if the size relationships are

mannitol>erythritol>ethylene glycol, which are more likely to lyse the cell?

A

ethylene glycol is the most permeable and will lyse the cells; (isoosmotic and hypotonic)
mannitol is not permeable and will not cause lysis of the cell. (isoosmotic and isotonic)

42
Q

neutral red is a base; in what conditions: acidic or basic, would it enter the cell?

A

it would enter the cell under basic conditions because it would be uncharged

43
Q

are drugs that are weak acids or weak bases more likely to be absorbed from the stomach?

A

drugs that are weak acids because the equilibrium would be shifted toward the uncharged acid

44
Q

what is an inhibitor of protein mediated transfer?

A

copper sulphate

45
Q

why do human RBCs lyse in glycerol while sheeps’ blood only lyse very slowly?

A

because sheep lack a protein mediator for glycerol

physiology lab exam (16 decks)

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