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FMS > [FMS] CBS - membrane transport > Flashcards

[FMS] CBS - membrane transport Flashcards

1
Q

what 4 characteristics must molecules have to freely cross the membrane by simple diffusion

A

Small
Uncharged
Hydrophobic
Non-polar

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2
Q

what molecules require specialist proteins to allow them to cross the membrane

A

charged polar molecules

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3
Q

give 5 examples of what hydrophobic molecules can pass through the membrane via simple diffusion

A

O2
N2
CO2
BENZENE
SHORT CHAIN FATTY ACIDS

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4
Q

give 3 examples of small uncharged polar molecules that can pass through the membrane via simple diffusion

A

H2O
UREA
GLYCEROL

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5
Q

what large, uncharged polar molecules can pass through the membrane

A

glucose
sucrose

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6
Q

what are the 5 transport mechanisms

A
  1. simple passive transport/diffusion
  2. facilitated diffusion
  3. gated ion channels
  4. primary active transport
  5. secondary active transport
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7
Q

what is passive transport

A

down concentration gradient

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8
Q

in passive transport what does the diffusion rate depend on?

A

diffusion rate depends on Partition Coefficient Solute

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9
Q

what does a high Partition Coefficient mean? what kind of molecule has a high Partition Coefficient?

A

Solutes that are more hydrophobic have a higher Partition Coefficient and
equilibrate more quickly

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10
Q

what is facilitated diffusion/carrier-mediated diffusion

A

down concentration gradient

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11
Q

what does facilitated diffusion/carrier-mediated diffusion need? give 3 examples

A

membrane protein required (ion channel) like:

  • aquaporin: water channel
  • GLUT glucose transporters
  • Cl-/HCO3- channel in erythrocytes
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12
Q

the transporter affinity for a solute is given by the?

A

Km

**LOWER Km ** = **HIGHER affinity **

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13
Q

where is GLUT1 transporter found?

A

high in erythrocytes, low in
skeletal muscle

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14
Q

where is GLUT2 transporter found?

A

Liver, pancreatic ßcells

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15
Q

where is GLUT3 transporter found?

A

Neurones

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16
Q

where is GLUT4 transporter found?

A

Muscle, Adipocytes

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17
Q

what is the function of GLUT1

A

Low Km (high affinity).

Mediates glucose uptake in many tissues.

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18
Q

what is the function of GLUT2

A

High Km (low affinity)

Transports glucose into
hepatocytes and pancreatic ß-cells when blood is high to regulate blood glucose levels.

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19
Q

does GLUT3 have a high or low Km

A

Low Km (high affinity)

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20
Q

high insulin levels indicate a high level of which GLUT transporter? 1,2,3,or 4

A

GLUT 4

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21
Q

what do gated ion channels do?

A
  • allows facilitated diffusion selective for different ions
  • exemplar ions: K+, Na+, Ca2+
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22
Q

2 types of gated ion channels

A

ligand-gated
e.g. acetylcholine and acetylcholine-gated Na+/K+ channel (acetylcholine receptor) on postsynaptic membranes

voltage-gated
e.g. Na+ and K+ channels in axons involved in nerve transduction in axons

23
Q

what is active transport?

A

Solutes move against a concentration gradient

24
Q

what 2 things does active transport require

A

membrane protein

energy via the hydrolysis of ATP

24
Q

give an example of primary active transport

A

Na+/K+ pump

24
Q

what is primary active transport?

A

needs energy from ATP hydrolysis

24
Q

Describe the NA+/K+ pump, what goes in and what goes out

A

2K+ IN

3NA+ OUT

25
Q

what does the Na+
/K+ pump consist of?

A

tetramer (α2β2)

26
Q

what is a co-transport system?

A

Pre-established gradient that’s used to drive transport of solute across membrane gainst a gradient

27
Q

what is used to establish the primary gradient in co-transport systems?

A

ATP hydrolysis

28
Q

2 types of cotransport systems

A

Symport
Antiport

29
Q

what is symport

A

transport of two solutes in the same direction

Symport = Same

30
Q

what is antiport

A

transport of two solutes in opposite direction

Antiport = Anti = Opposite

31
Q

what is uniport?

A

transport of ONE (uni) solutes in ONE direction

32
Q

what kind of cotransport system is SGLUT?

33
Q

What’s an example of an antiport cotransport system?

34
Q

what process is used to drive ca2+ export from cells in Na+/Ca2+ cotransporter

A

ATP hydrolysis

35
Q

Describe the NA+/Ca+ cotransporter, what goes in and what goes out

A

NA+ IN

CA2+ OUT

36
Q

what does digitoxin do?

A
  • inhibit Na+/K+ pump by blocking dephosphorylation step
  • [Na+] inside heart muscle increases
  • Na+ gradient lost
  • export of Ca2+ via antiport does not happen
  • [Ca2+] inside heart muscle increases and contraction increases
  • tachycardia
37
Q

what does oubain do?

A
  • inhibit Na+/K+ pump by blocking binding of K+
  • [Na+] inside heart muscle increases
  • Na+ gradient lost
  • export of Ca2+ via antiport does not happen
  • [Ca2+] inside heart muscle increases and contraction increases
  • tachycardia
38
Q

What causes Cystic Fibrosis?

A
  • reduced chloride transport
  • production of thick mucus
  • no movement of chloride ions means movement of water is not regulated
39
Q

what is CFTR

A

transmembrane protein

Chloride ions move by facilitated diffusion down concentration gradient – out of cell

ATP-gated ion channel

ABC (ATP-binding cassette) transporter family

Cytoplasmic regulatory domain is phosphorylated by cyclic AMP dependent protein kinase (PKA)

PKA activates and opens channel

40
Q

what does chloera toxin stimulate

A

Cholera toxin stimulates increase in cAMP level that activates CFTR and secretion of chloride ions

Na+ and water follow into lumen of via osmosis and the paracellular route

41
Q

what does Vibrio cholerae cause

A

electrolyte and fluid secretion

42
Q

how to treat chloera

A

Oral rehydration therapy includes high glucose concentration which
drives Na+ (and consequently Cl- and H2O) uptake into cells via SGLUT

43
Q

which GLUT transporter facilitates the transport of glucose into beta cells

44
Q

how is insulin secreted by beta cells, outline the events

A
  1. glucose transported into beta cells through facilitated diffusion by GLUT2
  2. metabolized glucose increases ATP level
  3. increases level of ATP/ADP ratio induces closure of cell-surface ATP-sensitive K+ (K-ATP) channels, leading to cell membrane depolarization
  4. Voltage-gated Ca2+ channels are opened, intracellular [Ca2+] increases
  5. Increase in [Ca2+] triggers the exocytosis of insulin stored in vesicles
45
Q

do keats quiz on membrane transport

A

https://keats.kcl.ac.uk/mod/quiz/view.php?id=6701135

46
Q

what is the Ion gradient of [Na+] and [K+] across plasma membrane (in cells vs blood plasma)

47
Q

Membranes are ____ permeable barriers that block passage of almost all ___ molecules

A

Selectively, hydrophillic

48
Q

summarise 1 example of primary active transport, and 2 examples of secondary active transport

49
Q

whats the difference between primary and secondary active transport

A

PRIMARY = uses energy from ATP hydrolysis

SECONDARY = uses energy stored in concentration gradient of ions

50
Q

where does:

diffusion
facilitated diffusion
primary active transport
and secondary active transport

get its energy from to drive the process

A

diffusion = kinetic energy of molecules

facilitated diffusion = kinetic energy of molecules + the assistance of transport proteins,

primary active transport = ATP hydrolysis

secondary active transport = energy stored in electrochemical gradients established by primary active transport or other cellular processes.

FMS (33 decks)

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