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Membrane transport Flashcards

(41 cards)

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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

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

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

Study These Flashcards
A
  • lower Km —> greater affinity
19
Q

What are aquaporins

Study These Flashcards
A
  • water channels for bulk H2O flow
20
Q

What is the structure of aquaporins

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

Where are aquaporins abundant

Study These Flashcards
A
  • erythrocytes

- kidney cells

22
Q

What is the Na+/K+ gradient

Study These Flashcards
A
  • high K+
  • low Na+
  • in cell
23
Q

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

Study These Flashcards
A

Na+/K+ ATPase

24
Q

What is the function of ATP-driven active transport

Study These Flashcards
A
  • control cell volume
  • make nerve & muscle cells excitable
  • facilitate ion-driven a-transport of amino acid & sugar
25
Describe the structure of Na+/K+ ATPase
Tetramer: 2a, 2b
26
What is the mechanism of Na+/K+ ATPase
- 3Na+ out - 2K+ in - polarises cell membrane - ATP hydrolysis —> conformational change - Na+ and K+ pumped against conc. gradient - coupled system
27
What’s coupled system
ATP not hydrolysed unless Na+ and K+ are transported
28
Give the two examples of ion-driven active transport
- symport | - antiport
29
Describe the symport
- Na+ conc. gradient - movement of glucose with Na+ - Na+/glucose transporter
30
Describe the antiport
- Na+ In - Ca2+ out - Na+/Ca2+ exchanger (- low Ca2+ Maintained)
31
What does digitalis cause in healthy ppl
Heart failure
32
What does digitalis cause in patients of congestive heart failure
Strengthen heart
33
What is digitalis replaced by nowadays
ACE inhibitors & diuretics
34
What is the mechanism of digitalis
- inhibit Na+/K+ ATPase - increase [Na+] inside - decrease Na+ grad - decrease Na+/Ca2+ exchange - increase [Ca2+] inside - enhance contraction of heart
35
What is the lining of the lumen
Epithelial cells
36
What does polarised epithelial cells mean
- apical membrane | - basolateral surface
37
Describe glucose transport in lumen
- 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
What are the different types of exocytosis
- constitutive: all cells, proteins | - regulated: specialised cells, Ca2+ dependant
39
Explain exocytosis in nerve terminal
- 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
What are the three types of endocytosis
- phagocytosis - pinocytosis - receptor-mediated endocytosis
41
Explain receptor-mediated endocytosis
- selective - chain-coated pits & vesicles - good for contracting low levels of macromolecules

IMS (18 decks)

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