JC1: Signalling, receptors, and pharmacology (1)

Question 1

What is Paul Ehrlich’s famous quote about receptors (include the modification)?

Answer 1

“A drug will not work unless it is specifically bound”

Question 2

What is the scientific name for aspirin?

Answer 2

Acetylsalicylic acid

Question 3

What is the molecular mechanism of action of aspirin?

Answer 3

Irreversible inhibition of cyclooxygenase (COX)

Question 4

What are the four properties of aspirin?

Answer 4

• Anti-inflammatory
• Antipyretic
• Analgesic
• Antiplatelet

Question 5

What are the four types of receptor (superfamily of proteins)? Give an example for each.

Answer 5

1. Ligand-gated ion channels, e.g. nicotinic acetylcholine receptor
2. Receptors with intrinsic enzymatic activity, e.g. insulin receptor
3. G protein-coupled receptors, e.g. β-adrenoceptor
4. Intracellular (nuclear) receptors, e.g. glucocorticoid receptors

Question 6

What is the substrate for the enzyme cyclooxygenase?

Answer 6

Arachidonic acid

Question 7

What are the substrates of adrenoceptors?

Answer 7

Adrenaline and noradrenaline

Question 8

What are endogenous ligands?

Answer 8

Ligands the body produces naturally

Question 9

What might exogenous ligands be?

Answer 9

Natural compounds (e.g. plant secondary metabolites) or laboratory-synthesised ligands

Question 10

What is an alternative name for adrenoceptors?

Answer 10

Adrenergic receptors

Question 11

What is the difference between noradrenaline and adrenaline?

Answer 11

Adrenaline has a methyl group at the end of the chain, whereas noradrenaline doesn’t

Question 12

What is a competitive inhibitor of adrenaline?

Answer 12

Propranolol

Question 13

What is the US name for isoprenaline?

Answer 13

Isoproterenol

Question 14

What is the US name for adrenaline/noradrenaline?

Answer 14

Epinephrine/norepinephrine

Question 15

What is the US name for salbutamol?

Answer 15

Albutertol

Question 16

How many times does a G protein-coupled receptor cross the lipid bilayer?

Answer 16

Seven times

Question 17

By what is ligand binding governed?

Answer 17

Kinetics of association and dissociation

Question 18

By what is ligand affinity governed?

Answer 18

Association vs. dissociation rate

Question 19

What is the law of mass action?

Answer 19

L + R ⇌ LR

(ligand + receptor ⇌ ligand-receptor complex)

Question 20

What is EC₅₀?

Answer 20

The effective concentration of ligand producing 50% of E_max (maximal response)

Question 21

What is potency?

Answer 21

ligand affinity + ability to cause a response

Question 22

What defines the ligand-receptor interaction?

Answer 22

Affinity and efficacy

Question 23

What is efficacy?

Answer 23

The ability to produce a desired or intended result

Question 24

How can radioligand binding be used to quantify the ligand-receptor affinity?

Answer 24

A radioactive form of the agonist or antagonist ligand is allowed to bind to cells (or membranes prepared from cells)

Low ligand concentration = low binding affinity
High ligand concentration = high binding affinity

Question 25

What is the downside of radioligand binding?

Answer 25

It gives no information on what happens subsequent to binding, i.e. whether the ligand possesses intrinisc efficacy

Question 26

Do agonists possess affinity for the receptor and intrinsic efficacy?

Answer 26

Yes

Question 27

Do antagonists possess affinity for the receptor and intrinsic efficacy?

Answer 27

No; they only posses affinity for the receptor

Question 28

What is intrinsic efficacy?

Answer 28

The ability to cause receptor activation

Question 29

What is the effect on the concentration-response curve of a competitive antagonist?

Answer 29

It shifts it to the right