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Pharmacology > ion channels and g proteins > Flashcards

ion channels and g proteins Flashcards

1
Q

3 steps of a signal transduction?

A

1) extracellular signal molecule activates membrane receptor
2) intracellular molecules transduced via a pathway
3) cell response activated

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2
Q

what is an extracellular signal? (Give examples)

A

A first messenger
- amines (adrenaline)
-steroid hormones
- proteins and peptides

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3
Q

what is an intracellular signal?

A

a second messenger molecule

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4
Q

what act as transducers between systems?

A

membrane proteins

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5
Q

4 classes of receptors?

A

ligand-gated ion channels
g-protein coupled receptors
enzyme-linked receptors
nuclear hormone receptors

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6
Q

what are ionotropic receptors?

A

ligand gated ion channels that form an ion pore

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7
Q

example of an ionotropic receptor

A

nicotinic acetylcholine receptor
Gaba A receptor

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8
Q

Stages of nicotinic Ach receptor?

A

1) binding of Ach opens channel for Na+
2) binding of nicotine
3) electrical event triggers response
4) calcium released
5) muscle contraction

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9
Q

What does Gaba A receptor inhibit?

A

inhibitor of neurotransmitters in CNS

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10
Q

What drug class activates Gaba A?

A

benzodiazepines

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11
Q

what are Gaba A receptors selective to?

A

chlorine ions

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12
Q

what are muscarinic receptors?(example)

A

type of Ach g protein coupled receptor

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13
Q

Examples of muscarinic receptors?

A

muscarinic ach receptor
Gaba B receptor- activated K+ channels

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14
Q

How many domains do GPCR have?

A

7 transmembrane domains

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15
Q

what are the 3 polypeptide chains of a g protein?

A

alpha, beta, gamma subunits

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16
Q

what does the alpha subunit bind to?

A

GTP/GDP

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17
Q

conditions of alpha-GDP?

A

resting condition - inactive g protein
high affinity to beta-gamma subunit

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18
Q

affinity of alpha-GTP?

A

low affinity to beta-gamma subunit

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19
Q

what does alpha subunit hydrolyse?

A

GTP to GDP

20
Q

structure of PKA?

A

2 catalytic 2 regulatory polypeptides

21
Q

what activates PKA?

A

binding of cAMP to R subunits

22
Q

what happens when C + R subunits are bound?

A

R supresses activity of C so PKA is inactive

23
Q

what happens when cAMP binds?

A

subunits dissociate
phosphorylation of other proteins allowed

24
Q

what responses rely on cAMP/PKA pathway?

A
  • kidney collecting duct
  • vascular smooth muscle and cardiac muscle
  • pancreas release of glucose
25
Q

what hydrolyses cAMP?

A

phosphodiesterase (PDE)

26
Q

what happens when cAMP unbinds?

A

increases R affinity to C
protein reassembles becomes inactive PKA

27
Q

what inhibits PDEs?

A

caffeine so cell response is prolonged
PKA active for longer

28
Q

what does desensitization of a receptor do?

A

feedback mechanism to reduce signal transduction
reduced cell response despite a sustained stimulus

29
Q

Different alpha subunits of g protein?

A

alpha s
alpha i
alpha q

30
Q

what does alpha s subunit do when activated?

A

simulates adenyl cyclase (AC)
uses ATP to produce cAMP
cAMP activates PKA
phosphorylation of target protein

31
Q

what does alpha i subunit do?

A

inhibits AC
decreases cAMP
inactivates PKA

32
Q

Receptor that couples to Gs?

A

beta2-adrenoreceptors - vasodilation decrease BP
vasopressin receptor

33
Q

Examples of receptor that couples to Gi?

A

alpha2 adrenoreceptors
A1/3 adenosine receptors
M2 muscarinic receptor

34
Q

Another class of g proteins?

A

Gq proteins with alpha q11 subunit

35
Q

what do Gq proteins do?

A

allow activation of phospholipase C (PLC)

36
Q

what does PLC do when stimulated by Gq protein?

A

cleaves PIP2 into IP3 and DAG

37
Q

what is IP3 and what does it do?

A

water-soluble part - hydrophilic
travels through cytosol to stimulate calcium release from ER
promotes cell response

38
Q

what does DAG do?

A

remains in membrane
recruits protein kinase C (PKC)

39
Q

What are IP3, Calcium and DAG examples of?

A

second messengers

40
Q

what are calcium mediated responses?

A

mediated by Ca2+ binding proteins

41
Q

example of Ca2+ binding protein?

A

calmodullin CaM

42
Q

what does CaM do?

A

binds 4 Ca2+ ions
complex activates PDE and CaM kinases (CaMKs)

43
Q

what do CaMKs do?

A

phosphorylate serine and threonine residues on proteins

44
Q

example of Gq protein receptor?

A

alpha 1 adrenoreceptor for vascular smooth muscle contraction
Vasoconstriction increase BP

45
Q

Effects of DAG?

A

presence increases activity of Ca2+ dependent protein kinase
phosphorylates PKC
mediates desensitization

Pharmacology (15 decks)

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