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PHSL 233 > L2 > Flashcards

L2 Flashcards

1
Q

we are made up of…..

A

18% protein

15% fat

7% minerals

and water
60% in men and 55% in women

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2
Q

out of your total body water (TBW) what % make up intra (ICF) and extracellular fluid (ECF)

A 
ICF = 66% of our TBW
ECF = 33% of our TBW
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3
Q

what makes up our ECF

A

our extracellular fluid is made up of…

75% interstitial fluid (between cells)
20% plasma
5% transcellular (inside epithelial lined spaces)

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4
Q

what is osmolarity

A

the concentration of a solution expressed as the total number of solute particles per litre.

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5
Q

what is the range of osmolarity in your total body water

A

285-300 mOsmol/L

it is a range because it is always changing

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6
Q

what is diffusion

A

the spontaneous movement of individual molecules from a region of high concentration to a region of low concentration thus making the concentration uniform

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7
Q

what do we know about the rate of diffusion

A

that it is very fast over short distances (eg at the cellular level) but decreases rapidly with distance

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8
Q

what is flux (J)

what does it discribe

A

it is the movement of soluble molecules

it describes the magnitude and direction of solute movement

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9
Q

what is Brownian motion

A

when solute molecules move independently of solvent molecules and other solute molecules

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10
Q

if you were going to plot the flux of a molecule, what would it be strongly dependent on

A

time

if you plot movement of the molecule every 30 sec the plot will look very different to if you did every hour

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11
Q

compare the net flux when the concentration of a solute is the same on both sides of a selective barrier compeered to when there is a difference in concentration

A

when the concentrations are different solutes will move in both directions BUT more will move from high to low therefore Jnet will not = 0

if the concentration is the same on each side the 2 unidirectional fluxes still occur but they are in equal and opposite directions. therefore Jnet = 0

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12
Q

what law describes net diffusional flux

A

Fick’s law

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13
Q

what is Fick’s law

A

that Jnet is proportional to number of moles per unit time (dn/dt)

dn/dt = -DA(dc/dx)

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14
Q

what does the diffusion coefficient reflect/tell us about

A

temp
viscosity
difference in size of solute molecules

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15
Q

in the fick’s law equation D, A and x are all constant, what value can they be incorporated into

A

permeability (P)

this is a experimentally determined coefficient

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16
Q

what is permeability

3 points

A

it is specific for a given membrane and solute which allows for the specific properties of those to be shown

it gives an interaction of the rate in which the solutes will cross the membrane (cm/s)

can be used to define the selectivity of a membrane

NOTE that it makes no assumptions about the mechanisms involved

17
Q

what is the permeability of K+

A

it is usually about 1

P K+&raquo_space; P Na+

permeability is usually a ratio

18
Q

what is fick’s law when applied to a membrane

A

Jnet = P (Co - Ci)

the steeper the concentration gradient the faster the rate of diffusion BUT only is the membrane is permeable to that solute

19
Q

what is a cell membrane

how thick is it

A

it is a physical and chemical barrier which separates the inside from the outside

it is a lipid bilayer with embedded proteins

it is about 5-10nm thick

phosphate rich heads on the outside

hydrophobic lipid tails on the inside

it is impermeable to water soluble molecules (except water because it is polar and very small)

its is soft and flexible

20
Q

does permeability allow for the fact that there are different mechanisms for different solutes to cross the cell membrane

A

yes

21
Q

can solubility diffusion be described by Fricks law? why?

A

yes

because it is a pure diffusional process and the solute dissolves (partitions) into the lipid bilayer and diffuses across the membrane

22
Q

what does solubility diffusion explain

hit (about a relationship)

A

the movement of most non-electrolytes (uncharged molecules)

it also explains the relationship between lipid solubility and permeability

23
Q

how does permeability correlate with lipid solubility and size

A

the more lipid soluable the solutes the more periable they are (homophobic vs hydrophilic)

for solutes with similar lipid solubilities the smaller the solute the more permeable it is

24
Q

what is an example of how the rate of diffusion changes with size and lipid solvability

(one example each)

A

ethylene glycol and di-ethylene glycol have the same lipid solubility but EG has a better permeability because it is smaller

glycerol is much smaller than glycerol try-acetate BUT the acetate groups make it more lipid soluable therefore glycerol try-acetate has a better permeability

25
Q

does solubility diffusion account for permeability of electrolytes? why?

A

no

often the permeability is much greater than predicted from their lipid solubility

26
Q

define selectivity sequences

A

p K+&raquo_space; P Na+

the permeability for a given ion can vary from cell to cell or within a cell. it can also vary with time

27
Q

what are some examples of how permeability of a cell membrane can change with time

A

during an action potential or following the effects of hormones

28
Q

temporary combination (of a solute) with a membrane protein accounts for movement of what

A

electrolytes and anomalous (not normal) non-electrolytes

29
Q

can membrane proteins be described by fick’s law? why not?

A

it cannot be described by Fick’s law because membrane proteins show…

slectivity
saturation kinetics
competition between similar species
inhibition

30
Q

what dramatically increases the net flux

A

membrane proteins such as channels, carryers, and active transport

31
Q

what are saturation kinetics

A

flux at the start will be much faster and then the curve will flatten out because the membrane proteins will become saturated therefore they will not be able to go any faster as there will be none left to carry out their task

32
Q

do transporters usually become saturated within a physiological context

A

no because the body does not usually contain levels of the solute where the proteins would become saturated

33
Q

what is a disease where the proteins have become saturated

A

diabetes happens when the glucose channels become saturated which is how you end up with glucose in the urine

34
Q

if channels were to become saturated at, the rate of transport can be varied by what

A

varying the kinetics of the transporter and by altering the number of transporters

PHSL 233 (31 decks)

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