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health & disease > L15 - what is a receptor: types & function > Flashcards

L15 - what is a receptor: types & function Flashcards

1
Q

what is pharmacology?

A

the science of drugs and how they act in a biological system.

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2
Q

drug that acts on effector causes what?

A

biological response

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3
Q

4 main protein drug targets

A
  1. receptors
  2. ion channels
  3. enzymes
  4. transporters
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4
Q

describe ion channels

A
  • proteins that are in plasma membrane
  • open in response to environmental cues (e.g memb depol)
  • allows channel specific ions to pass DOWN a conc. gradient

(the one that looks like a tunnel)

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5
Q

how can drugs modify ions channels?

A

via blockers or modulators

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6
Q

what are blockers in ion channels?

A

drug blocks ion channel so ions can’t pass through

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7
Q

what are modulators in ion channels?

A

modulators increase or decrease the chance of channel opening

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8
Q

what do enzymes do?

A
  • cause biochemical signals within cells + tissues
  • biological catalyst
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9
Q

3 types of enzyme receptors?

A
  1. inhibitors
  2. false substrates
  3. prodrug
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10
Q

what do enzyme inhibitors do?

A

prevent activity

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11
Q

what do enzyme false substrates do?

A

cause abnormal metabolite production (the product produced from substrate is different that what it should be)

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12
Q

what do prodrugs do?

A

enzymes will activate prodrugs into activate drug molecules

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13
Q

what are transporters/ carriers?

A
  • carries substances across membranes
  • move substances AGAINST conc. gradient (via AT)
  • diff from channel proteins as not open on both sides
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14
Q

inhibitors in transporters

A

they block the transport / carrier protein

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15
Q

false substrates in transporters

A

transporter recognises drug as something it wants to carry but it is not native so the drug has a different action

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16
Q

what are receptors?

A
  • proteins which are on surface of cell membranes
  • respond to exogenous cue
  • substance binds to receptor to produce a response
  • response allows physiological function
17
Q

3 types of substances for receptors

A
  1. agonists
  2. antagonists
  3. modulators
18
Q

agonist

A

something that activates a receptor

19
Q

antagonist

A

binds to receptor but doesn’t produce a response, so blocks receptor so essentially turns receptor off

20
Q

modulators

A

drugs that bind else where on receptors. decrease or increase receptor activation

21
Q

define ligand

A

something that binds

22
Q

second messenger

A

relay signal within a from receptor to effector

23
Q

signal transduction

A

sequence of second messengers that elicit biological response

24
Q

ligand receptor interactions

A
  1. ligand binds to receptor
  2. this causes conformational change of receptor
  3. leading to a cellular effect

so single causes action which causes response

25
Q

examples of cellular effects causes by ligand binding to receptor

A
  1. channel opens
  2. activation of linked enzyme
  3. effector proteins recruited
  4. intracellular transport
26
Q

4 types of receptor?

A
  1. ligand gated ion channels
  2. kinase linked receptors
  3. G protein coupled receptors
  4. nuclear receptors
27
Q

describe ligand gated ion channels

A
  1. not voltage gated
  2. channel opens when ligand binds
  3. allows specific ions to move through
  4. e.g ACh abd nicotinic acetylcholine receptors
28
Q

example of ligand gated ions channels: ACh + nicotinic receptors

A
  1. electrical impulse travels down pre-synaptic neuron
  2. triggers release of ACh from vesicles into synaptic cleft
  3. ACh acts on nAChRs on post synaptic neurone
  4. opens channel + allows Na+ to enter
  5. triggering impulse
29
Q

describe kinase

A
  • second messenger
  • enzyme uses ATP to phosphorylate a target
  • diff kinases act on diff targets
  • turns targets on and off
  • allows other second messengers to bind
30
Q

how do kinase linked receptors work?

A
  • sit on cell membrane as 2 halves
  • when ligand binds they come together to form dimer
  • dimer is active receptor
  • this activates kinase that is fused to the receptor
  • kinase phosphorylates target
  • causes response
31
Q

epidermal growth factor receptor (EGFR) and lung cancer

A
  • EGFR is a kinase linked receptor
  • it can promote cell growth
  • some lung cancers express. ore EGFR proteins causing more growth
  • so these cancers are susceptible to drugs that target EGFR
32
Q

describe G protein coupled receptors

A
  • has 7 transmembrane domains
  • coupled to a G protein
  • when ligand binds it activates G protein which will interact with effector
  • different GPCRs are coupled to diff G proteins so elicit diff responses
33
Q

describe GPCR activation (nucleotide exchange)

A
  1. resting state: GPCR is linked linked to G protein which is bound to GDP (guanasine di phosphate)
  2. when ligand binds the receptor activates + G protein switches out GDP for GTP
  3. this activates G protein and this GTP bound G protein associates with target effector to cause a response
  4. to move back to resting state, G protein will hydrolyse the GTP to make it GDP which makes G protein dissociate from effector
34
Q

muscarinic receptor and smooth muscle contraction

A
  • GPCR receptor example
  • how peristalsis works in intestine
  • neurons signal to smooth muscle cells
  • ACh released and acts on muscarinic M3 receptors
  • this activates G protein Gq
  • this causes Ca to enter smooth muscle cells causing contraction
  • forcing food through intestine
35
Q

what are antimuscarinics used for?

A

for irritable bowel syndrome

36
Q

nuclear receptors

A
  • associated with cell membrane
  • ligand enters cell and binds to receptor in cytoplasm
  • ligand receptor complex moves into nucleus
  • acts on gene expression
37
Q

oestrogen receptors and breast cancer

A
  • oestrogen receptor example of hormone nuclear receptor
  • important for equal maturation, gestation
  • some patients will have cancer cells that express more oestrogen receptors causing uncontrollable cell growth
38
Q

what are breast cancer patients given?

A

tamoxifen which targets oestrogen nuclear receptors

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