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IMS > Membrane transport > Flashcards

Membrane transport Flashcards

1
Q

What are the symptoms of cholera

A
  • severe diarrhoea

- vomiting

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2
Q

What is the prevalence of cholera

A
  • 3-5m cases year

- >100000 deaths year

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3
Q

What is the cause of cholera

A
  • vibrio cholerae bacteria

- cholera toxin

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4
Q

What is the treatment for cholera

A

ORT: water, salts & glucose

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5
Q

What is the function of the membrane

A
  • selectively permeable

- maintain constant internal environment eg pH

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6
Q

What are the two types of passive transport

A
  • simple diffusion

- facilitated diffusion

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7
Q

What are the two types of active transport

A
  • ATP-driven

- Ion-driven

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8
Q

Describe simple diffusion

A
  • no energy required
  • small molecules
  • co specificity
  • conc. gradient
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9
Q

Describe facilitated diffusion

A
  • conc. gradient
  • no energy
  • depend on integral proteins, temp., pH, etc
  • specific
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10
Q

What is an ionophore

A

Ion carrier

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11
Q

Why is ionophore produced by bacteria & how does it do that

A
  • antibiotic, destroy rival bacteria

- discharge ion gradients of target cell

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12
Q

Give an example of carrier ionophore

A
  • valinomycin
  • hydrophobic molcules —> carry ions
  • specific to transport K+ —> down its conc. gradient
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13
Q

Give an example of channel-forming ionophore

A
  • gramicidin A

- made of alternating L & D amino acids

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14
Q

What is the function of ion channels

A
  • rapid and gated passage of anions & cations
  • highly selective
  • allow ion flow
  • maintain osmotic balance
  • signal transduction
  • nerve impulse
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15
Q

Describe glucose transport

A
  • facilitated diffusion

- integral protein, GLUT 1

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16
Q

What is the structure of GLUT1

A

12 transmembrane a-helices

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17
Q

What happens to glucose once entering the cell

A
  • glucose —> glucose-6-phosphate
  • hexokinase
  • maintain conc. gradient
18
Q

What is the relationship between Km and affinity of transporter for molecule

A
  • lower Km —> greater affinity
19
Q

What are aquaporins

A
  • water channels for bulk H2O flow
20
Q

What is the structure of aquaporins

A
  • 28 kDa protein
  • 6 transmembrane a-helices
  • 4 pores for H2O
21
Q

Where are aquaporins abundant

A
  • erythrocytes

- kidney cells

22
Q

What is the Na+/K+ gradient

A
  • high K+
  • low Na+
  • in cell
23
Q

What is the mechanism of ATP-driven active transport maintained by

A

Na+/K+ ATPase

24
Q

What is the function of ATP-driven active transport

A
  • control cell volume
  • make nerve & muscle cells excitable
  • facilitate ion-driven a-transport of amino acid & sugar
25
Q

Describe the structure of Na+/K+ ATPase

A

Tetramer: 2a, 2b

26
Q

What is the mechanism of Na+/K+ ATPase

A
  • 3Na+ out
  • 2K+ in
  • polarises cell membrane
  • ATP hydrolysis —> conformational change
  • Na+ and K+ pumped against conc. gradient
  • coupled system
27
Q

What’s coupled system

A

ATP not hydrolysed unless Na+ and K+ are transported

28
Q

Give the two examples of ion-driven active transport

A
  • symport

- antiport

29
Q

Describe the symport

A
  • Na+ conc. gradient
  • movement of glucose with Na+
  • Na+/glucose transporter
30
Q

Describe the antiport

A
  • Na+ In
  • Ca2+ out
  • Na+/Ca2+ exchanger
    (- low Ca2+ Maintained)
31
Q

What does digitalis cause in healthy ppl

A

Heart failure

32
Q

What does digitalis cause in patients of congestive heart failure

A

Strengthen heart

33
Q

What is digitalis replaced by nowadays

A

ACE inhibitors & diuretics

34
Q

What is the mechanism of digitalis

A
  • inhibit Na+/K+ ATPase
  • increase [Na+] inside
  • decrease Na+ grad
  • decrease Na+/Ca2+ exchange
  • increase [Ca2+] inside
  • enhance contraction of heart
35
Q

What is the lining of the lumen

A

Epithelial cells

36
Q

What does polarised epithelial cells mean

A
  • apical membrane

- basolateral surface

37
Q

Describe glucose transport in lumen

A
  • Na+/glucose symport transporter transport glucose into epithelial cells through apical membrane down conc. gradient
  • glucose diffused across basolateral membrane through glucose transporter, facilitated diffusion
  • Na+ level is maintained low due to Na+/K+ ATPase in basolateral membrane
  • increases osmotic pressure, water flow follows glucose diffusion
38
Q

What are the different types of exocytosis

A
  • constitutive: all cells, proteins

- regulated: specialised cells, Ca2+ dependant

39
Q

Explain exocytosis in nerve terminal

A
  • nerve stimulation —> depolarisation —> activated voltage-gated ion channels —> Ca2+ enter nerve terminal rapidly —> synaptic vesicles with neurotransmitters fuse with synaptic membrane —> content released in synaptic cleft —> stimulate receptors in post-synaptic clefts
40
Q

What are the three types of endocytosis

A
  • phagocytosis
  • pinocytosis
  • receptor-mediated endocytosis
41
Q

Explain receptor-mediated endocytosis

A
  • selective
  • chain-coated pits & vesicles
  • good for contracting low levels of macromolecules

IMS (18 decks)

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