Concept of agonists and antagonists

Question 1

What is the difference between an agonist and an antagonist (2)

Answer 1

1. An agonist binds to a receptor to generate a response
2. An antagonist binds to a receptor and generates no response

Question 2

What is an agonist

Answer 2

A drug or endogenous chemical messenger molecule (hormone) that occupies and activates a receptor to produce a biological response

Question 3

What is a partial agonist

Answer 3

A drug or endogenous chemical messenger molecule (hormone) that occupies and activates a receptor but can only achieve a partial biological response

Question 4

What is an inverse agonist (2)

Answer 4

1. A drug or endogenous chemical messenger molecule (hormone) that occupies and activates a receptor to produce the opposite biological response to the agonist.
2. e.g. relaxation instead of contraction of a muscle

Question 5

What is an antagonist

Answer 5

A drug that occupies a receptor but does NOT produce a biological response (may block or hinder the action of agonists)

Question 6

What is a competitive (reversible) antagonist (4)

Answer 6

1. Compete with agonists for the same receptor
2. If the agonist wins, a response occurs
3. If the antagonist wins, no response occurs because it blocks the action of the agonist
4. Competitive antagonists make agonists look less potent

Question 7

What is a non-competitive (irreversible) antagonist (3)

Answer 7

1. Bind receptors permanently (covalent bonding)
2. Can block the agonist binding site or block the response to an agonist
3. Non-competitive antagonists reduce the maximum response (efficacy) that an agonist can produce