Receptors

Question 1

What are the 4 classes of proteins targeted by drugs?

Answer 1

Enzymes
Transporters
Ion channels
Receptors

Question 2

Define Receptors

Answer 2

Proteins that serve as recognition sites and allow binding of chemical mediators

Question 3

What is the function of receptors ?

Answer 3

Regulation of cellular processes
Chemical recognition and binding
Intracellular signal generation

Question 4

Name 2 drugs which interfere with ion channels

Answer 4

Lignocaine (voltage gated sodium channel blocker)
Gabapentin (voltage gated calcium channel blocker)

Question 5

How many aa segments do transmembrane receptors span?

Answer 5

20-25 hydrophobic amino acids

Question 6

What is a type 1 receptor?

Answer 6

Ligand gated ion channel

Question 7

Is a type 1 receptor ionotropic or metabotropic?

Answer 7

Ionotropic

Question 8

How do drugs interact with membrane receptors ?

Answer 8

Via the extracellular ligand binding domain, travels through the transmembrane segments, into the cytoplasm via the cytoplasmic domain

Question 9

What is the type 2 receptor?

Answer 9

G-protein coupled receptor

Question 10

Is the type 2 receptor ionotropic or metabotropic?

Answer 10

Metabotropic

Question 11

What is the effector for a type 1 ?

Answer 11

An ion channel

Question 12

What is the effector for type 2?

Answer 12

Channel or enzyme

Question 13

What is the type 3 receptor?

Answer 13

Receptor kinase

Question 14

What is the type 4 receptor?

Answer 14

Nuclear receptor

Question 15

How does a type 4 receptor couple?

Answer 15

Via DNA

Question 16

How is a type 4 different to type 1,2&3?

Answer 16

Type 4 is an intracellular receptor whereas the others are all membrane receptors

Question 17

Define ligand

Answer 17

Any molecule that binds to a receptor

Question 18

Define an agonist

Answer 18

An agonist produces a response in the cell after binding to a receptor

Question 19

Define an antagonist

Answer 19

An antagonist inhibits or prevents a response after a possible receptor binding

Question 20

How does a type 4 receptor work?

Answer 20

Soluble receptors that sense lipid and hormone signals and modulate gene transcription. The binding ligand must be able to cross the plasma membrane

Question 21

Give an example of an agonist

Answer 21

Pilocarpine
Nicotine
Acetylcholine
Morphine

Question 22

Give an example of an antagonist

Answer 22

Atropine
Curare

Question 23

How does type 1 transduce a signal ?

Answer 23

Hyperpolarisation or depolarisation

Question 24

How does type 2 transduce a signal?

Answer 24

Change in excitability or
Second messengers (protein phosphorylation, Ca2+ release/other) which produces a cellular effect

Question 25

How do type 3 transduce a signal?

Answer 25

Protein phosphorylation -> Gene transcription -> Protein synthesis -> Cellular effects

Question 26

How does type 4 transduce a signal?

Answer 26

Ligand binds to receptor in the nucleus -> Gene transcription -> Leaves nucleus and protein synthesis occurs -> Cellular effects

Question 27

Example of type 1

Answer 27

Nicotinic ACh receptor

Question 28

Example of type 2

Answer 28

Muscarinic ACh receptor

Question 29

Example of type 3

Answer 29

Cytokine receptor

Question 30

Example of type 4

Answer 30

Oestrogen receptor

Question 31

What is an ionotropic receptor?

Answer 31

Receptors that are ion channels

Question 32

What is an endogenous agonist?

Answer 32

Fast/classical neurotransmitters stored in synaptic vesicles, composed of 3-5 subunits with a central aqueous pore.

Question 33

When does a channel close?

Answer 33

When an agonist is removed or When a receptor enters a desensitised state

Question 34

What does activation of ionotropic receptors by excitatory neurotransmitters cause? Give an example and its antagonist

Answer 34

Membrane depolarization Action potential firing Example: Nicotinic Acetylcholine Receptor, antagonist = tubocurarine

Question 35

What does activation of ionotropic receptors by inhibitory neurotransmitters cause? Give an example

Answer 35

Inhibits membrane depolarisation Reduces action potential firing Example: GABAaRs

Question 36

Structure of type 1

Answer 36

Pentameric assembly Cys-loop type

Question 37

Structure of type 2

Answer 37

Tetrameric assembly ionotropic glutamate type

Question 38

Structure of type 3

Answer 38

Trimeric assembly P2X type

Question 39

Structure of type 4

Answer 39

Tetrameric assembly Calcium release type

Question 40

Why may cells express different receptors?

Answer 40

To coordinate their responses to changes in external environments and maintain homeostasis

Question 41

What does the physiological consequence of a drug rely on?

Answer 41

Specificity