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Physiology > membrane transport > Flashcards

membrane transport Flashcards

1
Q

ions found mostly in extraceullar fluid

A

Na and Cl

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2
Q

ions found mostly in cells

A

K and PO43+

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3
Q

rate of solute movement across a membrane

A

P x C

where P is the permeability coefficient and C is the concentration gradient

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4
Q

hydrophobic molecules

A

diffuse easily across the membrane

O2, CO2, N2, steroid hormones

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5
Q

small uncharged polar molecules

A

kinda go through the plasma membrane

water, urea, glycerol, NH3

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6
Q

large uncharged polar molecules

A

mostly don’t go through the membrane

glucose and sucrose

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7
Q

ions

A

don’t go through the plasma membrane at all

protons, sodium, HCO3-, K+, Ca2+, Cl-, Mg2+

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8
Q

osmolarity

A

the concentration of everything but water

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9
Q

why is osmolarity sometimes hard too calculate

A
  • Depends on how much stuff dissociates

- Osmolaritty of proteins and macromolecules hard to predict depends on dissociation

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10
Q

osmolarity of intracellular fluid

A
  • Osmolarty of intracellular fluid is 300mOsmol/L
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11
Q

aquaporins

A

channel allowing water to move

allows bidirectional movement

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12
Q

tonicity

A

whether a cell swells or shrinks due to osmosis

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13
Q

isotonic

A

cell stays the same size

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14
Q

hypertonic

A

has more solutes so the cell shrinks

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15
Q

hypotonic

A

has less solute so the cell swells or bursts

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16
Q

iso osmolar

A

same osmotic value

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17
Q

why is iso-osmolar not the same as isotonic

A

solutes can move through membrane as well

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18
Q

when is iso osmolar the same as isotonic

A

when dealing with solutes that don’t move across the membrane

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19
Q

channel and transporter mediated transport is powered by

A

concentration gradient

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20
Q

pump mediated transport is powered by

A

ATP

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21
Q

pores and channels

A
  • Water filled pores and channels increase permeability
    • Pores and channels can be selective eg. Aquaporin for water
    • Channels are gated pores allow control of permeability
22
Q

channels are different to pores because

A
  • Channels are gated pores allow control of permeability
23
Q

3 types of gated channels

A

mechanically gated, ligand gated, voltage gated

24
Q

mechanically gated channels

A

shut when there is no tension

25
Q

ligand gated channels

A

○ Chemical molecule - ligand - opens the channels

○ Can be extracellular or intracellular ligand

26
Q

voltage gated channels

A

○ Most cells are negative on the inside and positive on the outside
○ When the voltage changes the channels open

27
Q

carrier proteins and transport proteins

A
  • Facilitated diffusion
    • Conformational change -> transport
    • Energy from concentration gradient
28
Q

uriporters

A

○ Transport a signle solute from one side of the membrane to another

29
Q
  • Co-transporters
A

○ Transfer of one solute depends on the simultaneous transport of a second solute (coupled transport)

30
Q

2 types of co transporters

A

○ Symporters
§ Transfer second solute in the same direction as the first
○ Antiporters
§ Transfer the second molecule in the opposite direction tto the first

31
Q

SGLT1

A
  • Sodium-dependant glucose transporter
    • Na+ and glucose transport
    • Symporter
32
Q

Active transport - pumps

A
  • Pumps use the chemical potential energy to pump molecules up hill against their concentration gradient
    • The pump is effectively a carrier being forced to operate in reverse (both are called transporters/facilitated diffusion)
33
Q

ATP-binding cassette transporters - ABCs

A
  • bind specific molecules and use ATP energy to transport them across phospholipid bilayers
    • Huge superfamily (many transporters = many target molecules)
34
Q

ABC transporter example

A

ABCA/ABCG - exports cholesterol out of cells

35
Q

The Na+/K+ pump

A
  • Uses ATP
    • Antiporter
    • All cells have this pump and it uses 33% of it’s cellular energy
36
Q

how many ions does the NA/K pump transport

A
  • Pumps 3x Na+ put and 2x K+ in per cycle

- Uses 1xATP molecule

37
Q

electrical effect of Na/K pump

A
  • Electrogenic - net movement of +ve charge out of cell
38
Q

inside of the cell is charged

A

negatively

39
Q

secondary active transport

A

establishing the Na/K gradient and using it to pump other things in and out of the cell

40
Q

example of secondary active transport

A

SGLT1 symporter of Na and glucose

allows glucose uptake

41
Q

2 types of exocytosis

A

constitutive and regulated

42
Q

constitutive exocytosis

A

§ Produce a protein and put it in a vessicle and it has unregulated membrane fusion

43
Q

regulated exocytosis

A

§ Regulated membrane fusion

44
Q

endocytosis

A

○ Big things (phagocytosis), little things (pinocytosis)

○ Can be highly specific (receptor mediated)

45
Q

what products the vesicle

A

coat protein - clatherin

46
Q

clatherin is a

A

coat protein

47
Q

how does the vesicle know where to go

A

Rab protein

48
Q

rab effector

A

moves vessicle to the plasma membrane

49
Q

SNAREs

A

mediate fusion

50
Q

v-snares

A

on the vesicle

51
Q

t-snares

A

on the target membrane

Physiology (13 decks)

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