antagonists and agonists

Question 1

what is meant by the term agonist

Answer 1

an agonist is a drug that acts by binding to a receptor in order to produce a cellular response

Question 2

what is meant by the term antagonist

Answer 2

an antagonist is a drug that acts by reducing or blocking the actions of an agonist by binding to the same receptor

Question 3

describe what is meant by the term affinity

Answer 3

affinity = the strength of association between a ligand and receptor
for example low affinity = fast dissociation rate
high affinity = slow dissociation rate

Question 4

what is the affinity determined by

Answer 4

determined by the chemical bonds between a ligand and receptor, ionic bonds, H bonds and aromatic interactions

Question 5

what is meant by the term efficacy

Answer 5

efficacy = the ability of an agonist to stimulate a cellular response
if efficacy is low then equilibrium will be in favour of no response

Question 6

what properties to antagonists have, in terms of efficacy and affinity

Answer 6

they have high affinity and low efficacy, because they bind to the receptors but do not activate them

Question 7

describe what is meant by competitive antagonism

Answer 7

this is when the antagonist binds to the same(orthosteric) site on the receptor as the agonist would, this is reversible by increasing agonist conc.

Question 8

describe what is meant by non-competitive antagonism

Answer 8

antagonist binds to separate(allosteric) site, when it is attached to this site activation cant occur but agonist may still bind to orthosteric site