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I've got kidney disease > Lecture 2: Diffusion > Flashcards

Lecture 2: Diffusion Flashcards

1
Q

What percentage of women is made up of water?

A

about 55%

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2
Q

What percentage of men is made up of water?

A

about 60%

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3
Q

What percentage of total body water is made up of ICF?

A

66%

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4
Q

What is ICF and where is it?

A

intracellular fluid

this is inside cells

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5
Q

What percentage of total body water is made up of ECF?

A

33%

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6
Q

What is the ECF and where is it?

A

extracellular fluid

fluid not inside cells

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7
Q

What are the three components of ECF and what percentage of ECF do they make up?

A

Interstitial fluid: 75% ECF
Plasma: 20%
Transcellular: 5%

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8
Q

Where is interstitial fluid?

A

in between cells

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9
Q

What is plasma?

A

it is a solution in blood

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10
Q

Where is transcellular fluid?

A

inside the epithelial lined space

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11
Q

What are the three main ions in the ECF and ICF that determine membrane potentials?

A

Na+
K+
Cl-

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12
Q

What is the osmolarity of plasma (ICF)?

A

285 mOsmolL-1

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13
Q

What is the osmolarity of muscle (ICF)?

A

285 mOsmolL-1

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14
Q

What is the main ion in the ICF and what is its concentration?

A

K+

150 mmolL-1

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15
Q

What is the main ion in the ECF and what is it’s concentration?

A

Na+

150 mmolL-1

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16
Q

What is the range for osmolarity?

A

285 - 300 mOsmolL-1

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17
Q

Define diffusion

A

Spontaneous movement of individual molecules from a region of high concentration to a region of low concentration

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18
Q

When is the rate of diffusion very fast?

A

over very short distances

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19
Q

Rate of diffusion decreases rapidly with what?

A

distance

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20
Q

Solute molecules move independently of what?

A

solvent molecules and other solute molecules

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21
Q

What does flux describe?

A

the magnitude and direction of solute movement

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22
Q

What does the net diffusional flux result from?

A

two unidirectional fluxes

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23
Q

What is flux?

A

movement of the solute molecules

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24
Q

What is the net flux?

A

net combination of the flux in one direction and the flux in the other direction

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25
Q

If the concentration of the two solutions is different, the net flux is positive/negative/zero?

A

positive

26
Q

If the concentration of the two solutions is the same the net flux is positive/negative/zero? What happens here?

A

zero

there is two unidirectional fluxes but they are equal and opposite

27
Q

What is Fick’s Law?

A

Jnet ∝ dn/dt = -D.A (dc/dx)

28
Q

What do we simplify Fick’s Law to be and why is this?

A

Jnet = PΔC
This is because D, A and Δx are all constant for a given membrane and are incorporated into a single experimentally determined permeability coefficient, P

29
Q

Define permeability

A

a measure of how fast solute crosses the membrane

30
Q

Permeability is specific for what?

A

a given membrane and solute

31
Q

Permeability gives an indication of what?

A

the rate of movement (in cms-1)

32
Q

What can permeability be used to define? Give an example

A

The selectivity of a membrane. For a given cell membrane, PK&raquo_space; PNa

33
Q

Permeability makes no assumptions about the mechanisms involved. What does this mean?

A

It doesn’t tell you anything about how the solutes get through eg. through diffusion or through a transporter

34
Q

What is another way of writing Jnet = PΔC? What does this tell us?

A

Jnet = P (Co - Ci)

This means the steeper the concentration, the faster the rate of diffusion

35
Q

The steeper the concentration, the faster the rate of diffusion but only if..

A

the cell is permeable to that solute

36
Q

How is permeability obtained?

A

From the modification of Fick’s Law:

the concentration is given by the difference in concentration inside and outside the cell

37
Q

What is the cell plasma membrane?

A

a physical and chemical barrier that separated the inside from the outside of the cell

38
Q

The plasma membrane is a __________ _________ embedded with ________

A

lipid bilayer

proteins

39
Q

In the plasma membrane, the phosphate-rich heads are on the inside/outside

A

outside

40
Q

In the plasma membrane the hydrophobic lipid tails are in the inside/outside

A

inside

41
Q

What is the plasma membrane impermeable to? What does this exclude? Why is this?

A

it is impermeable to water-soluble molecules except water because it is polar

42
Q

P allows for the fact that there are different what?

A

mechanisms for different solutes to cross cell membranes

43
Q

What does solubility diffusion refer to?

A

the movement of most non-electrolytes

44
Q

Why can solubility diffusion be described by Fick’s law?

A

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

45
Q

There is a positive/negative relationship between solubility and permeability. What are the exceptions?

A

positive

water, urea

46
Q

The more lipid soluble the solutes are, the more/less permeable they are

A

more

47
Q

For solutes with similar lipid solubilities, the smaller the solute, the more/less permeable the solute`

A

more

48
Q

Permeability correlates with size. The smaller the molecule the faster/slower the rate of diffusion

A

faster

49
Q

Permeability correlates with lipid solubility. The more soluble the solutes, the more/less permeable they are

A

more

50
Q

What is interesting about adding acetates to molecules and their fat solubility?

A

adding more acetate increases fat solubility although it increases the size

51
Q

Solubility diffusion does not account for what?

A

Permeability of electrolytes. Often the permeability is much greater than predicted from their lipid solubility

52
Q

What can the permeability for a given ion vary from and with?

A

it can vary from time to time and can vary with time

53
Q

What does the temporary combination with membrane proteins account for?

A

the movements of electrolytes and anomalous non-electrolytes

54
Q

Why is combination with membrane proteins is not described by Fick’s law?

A

because it shows

  • selectivity
  • saturation kinetics
  • competition between similar species
  • inhibition
55
Q

Even though protein mediated transport is not described by Fick’s law, __________ is still a useful measure

A

permeability

56
Q

What does protein-mediated transport mean?

A

transport aided by proteins such as channels and transporters

57
Q

Transporters may not be saturated over what?

A

physiological concentration range

58
Q

Even when saturated at physiological concentrations, the rate of transport can be varied by what two things?

A
  • varying kinetics of transporter

- altering the number of transporters

59
Q

As the ΔC or driving force increases, what happens to Jnet?

A

it increases at a decreasing rate and then levels off as the transporters become saturated

60
Q

At low concentrations, there is a smaller/larger influx

A

larger

I've got kidney disease (43 decks)

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