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principles of normal function > week 2 forces acting across membranes > Flashcards

week 2 forces acting across membranes Flashcards

1
Q

what are aquaporin channels

A

channels that are permanately open to water

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2
Q

what is the [K+] like in ICF and ECF

A

[K+] is high in intracellular fluid, low in extracellular fluid

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3
Q

what is the [Na+] like in ICF and ECF

A

[Na+] is low in ICF and high in ECF

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4
Q

what can pass freely through the capillary wall

A

ions
so they can exchange between plasma and ISF
they do NOT penetrate the cell membrane!!!!!!

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5
Q

where can gases pass through

A

gases can pass freely through all three compartments (plasma, ICF, ISF)
nutrients and waste also pass easily but sometimes need help crossing the cell membrane

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6
Q

what are 7 important things to remeber about membranes

A
  1. cell membrane is a selective barrier
  2. permeability can vary
    (may increase or decrease at certain times)
  3. membranes are dynamic
    (continually being formed and maintained/dismantled and metabolised)
  4. membrane is double layer of lipid
  5. membranes are flexible
    (because of the fatty acids they can act like an oil)
  6. membranes are insulators, so no ions can pass
  7. membranes are embedded with proteins
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7
Q

what are the 5 common functions of membrane proteins

A
  • receptors
  • transport
  • enzymes
  • structural (anchorage)
  • communication
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8
Q

what are the two types of transport proteins

A
  • channel proteins: can be open (water) or gated (ions)

- carrier mediated transport proteins (transporters)

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9
Q

what do structural proteins do

A

they anchor the cell membrane to the intracellular skeleton, to the extracellular matrix (collagen) and/or to other cells

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10
Q

what do glycoproteins do

A
  • membrane protein with carbohydrate attached to the external surface
  • act as markers that tell the immune system whether a cell is one of our own of a foreign cell
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11
Q

do membranes differ in their protein content

A

yes
myelin = 18%
plasma membranes of cells = typically 50%
membranes involved in energy transduction = 75%

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12
Q

is there a physical barrier to water movement

A

no

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13
Q

what is an electrochemical gradient

A
  • large concentration gradient exist between ICF and ECF for ions
  • because it is ions creating the concentration gradient there is also a difference in charge. this creates an electrical gradient
  • these two forces make the electrochemical gradient which ultimately drives the direction of passive movement
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14
Q

what are the mechanisms of movement across membranes

A
  1. diffusion (passive or facilitated - channels or transporters)
  2. active transport
  3. osmosis
  4. filtration (movement between plasma and ISF)
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15
Q

what is endocytosis

A

invagination of membrane to form vesicle which then disintegrates inside cell

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16
Q

what is exocytosis

A

invagination of cell membrane to form vesicle and substances are released outside of cell

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17
Q

what happens in passive diffusion

A

substances move directly through the lipid bilayer

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18
Q

what are the characteristics of molecules which can pass through the lipid bilayer

A
  1. small
  2. uncharged
  3. lipophilic (hydrophobic)
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19
Q

what is a molecule that is moved across the membrane via transporter

A

glucose

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20
Q

how does sodium potassium pump work

A
  • 3 Na+ bind from inside cell
  • ATPase is phosphorylated and changes conformation
  • 3 Na+ released to outside into ECF
  • 2 K+ bind from outside cell
  • ATPase is dephosphorylated and changes conformation
  • 2 K+ released inside cell
21
Q

what is osmotic pressure

A

the pressure applied to oppose osmosis

22
Q

what are the protein concentrations like in the cell compartments

A 
plasma = [plasma protein] is high
ISF = [protein] is low
ICF = [protein] high
23
Q

what is the osmolarity of normal human plasma

A

285 mOsmol/l
it is the same in cell
often rounded to 300

24
Q

what is osmolarity

A

the total number of particles in solution

25
Q

what is tonicity

A

the number of non-penetrating particles in solution

e.g. ions

26
Q

what is an isometric solution

A

has the same total number of solute particles as normal ECF (plasma)

27
Q

what is a hypo-osmotic solution

A

solutions with fewer total solute particles

28
Q

what is hyper-osmotic

A

solutions with greater number of total solute particles

29
Q

what is an isotonic solution

A

solution with the same number of non-penetrating solute particles as normal ECF (plasma)

30
Q

what is a hypotonic solution

A

solution with fewer non-penetrating solute particles

31
Q

what is a hypertonic solution

A

solutions with greater number of non-penetrating solute particles

32
Q

is urea penetrating or non-penetrating

A

penetrating

33
Q

if we have an isosmotic solution and all those particles are non-penetrating what is the tonicity

A

isotonic

34
Q

if we have an isosmotic solution and half the concentration is penetrating and the other half is non-penetrating what is the tonicity

A

hypotonic

35
Q

if all the particles in a hyper osmotic solution are non-penetrating what is the tonicity

A

hypertonic

36
Q

if a hyper osmotic solution has the same number of non-penetrating particles as ECF what is the tonicity

A

isotonic

37
Q

if a hyper osmotic solution has less penetrating particles than normal what is the tonicity

A

hypotonic

38
Q

what tonicities can isosmotic solutions be

A

isotonic or hypotonic

39
Q

what tonicities can hyperosmotic solutions be

A

isotonic, hypotonic or hypertonic

40
Q

what tonicities can hypo osmotic solutions be

A

hypotonic

41
Q

what is normal tonicity of ECF

A

close to 285 mosmol/L

42
Q

what happens to cells in hypotonic solutions

A

they swell

43
Q

what happens to cells in hypertonic solutions

A

they shrink

44
Q

when should you transfuse a patient with pure water

A

never!!

45
Q

what is the tonicity of saline solution

A

0.9% saline is isotonic

46
Q

what is the osmolarity of 1M solution of NaCl

A

2 osmoles/l

47
Q

what is the osmolarity of 1mM solution of glucose

A

1 mosmole/l

48
Q

what is the most sensitive organ to changes in tonicity

A

the brain

principles of normal function (15 decks)

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