L15 - what is a receptor: types & function

Question 1

what is pharmacology?

Answer 1

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

Question 2

drug that acts on effector causes what?

Answer 2

biological response

Question 3

4 main protein drug targets

Answer 3

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

Question 4

describe ion channels

Answer 4

• 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)

Question 5

how can drugs modify ions channels?

Answer 5

via blockers or modulators

Question 6

what are blockers in ion channels?

Answer 6

drug blocks ion channel so ions can’t pass through

Question 7

what are modulators in ion channels?

Answer 7

modulators increase or decrease the chance of channel opening

Question 8

what do enzymes do?

Answer 8

• cause biochemical signals within cells + tissues
• biological catalyst

Question 9

3 types of enzyme receptors?

Answer 9

1. inhibitors
2. false substrates
3. prodrug

Question 10

what do enzyme inhibitors do?

Answer 10

prevent activity

Question 11

what do enzyme false substrates do?

Answer 11

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

Question 12

what do prodrugs do?

Answer 12

enzymes will activate prodrugs into activate drug molecules

Question 13

what are transporters/ carriers?

Answer 13

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

Question 14

inhibitors in transporters

Answer 14

they block the transport / carrier protein

Question 15

false substrates in transporters

Answer 15

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

Question 16

what are receptors?

Answer 16

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

Question 17

3 types of substances for receptors

Answer 17

1. agonists
2. antagonists
3. modulators

Question 18

agonist

Answer 18

something that activates a receptor

Question 19

antagonist

Answer 19

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

Question 20

modulators

Answer 20

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

Question 21

define ligand

Answer 21

something that binds

Question 22

second messenger

Answer 22

relay signal within a from receptor to effector

Question 23

signal transduction

Answer 23

sequence of second messengers that elicit biological response

Question 24

ligand receptor interactions

Answer 24

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

Question 25

examples of cellular effects causes by ligand binding to receptor

Answer 25

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

Question 26

4 types of receptor?

Answer 26

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

Question 27

describe ligand gated ion channels

Answer 27

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

Question 28

example of ligand gated ions channels: ACh + nicotinic receptors

Answer 28

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

Question 29

describe kinase

Answer 29

- 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

Question 30

how do kinase linked receptors work?

Answer 30

- 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

Question 31

epidermal growth factor receptor (EGFR) and lung cancer

Answer 31

- 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

Question 32

describe G protein coupled receptors

Answer 32

- 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

Question 33

describe GPCR activation (nucleotide exchange)

Answer 33

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

Question 34

muscarinic receptor and smooth muscle contraction

Answer 34

- 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

Question 35

what are antimuscarinics used for?

Answer 35

for irritable bowel syndrome

Question 36

nuclear receptors

Answer 36

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

Question 37

oestrogen receptors and breast cancer

Answer 37

- 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

Question 38

what are breast cancer patients given?

Answer 38

tamoxifen which targets oestrogen nuclear receptors