Lecture 1 and 2 (Part 3) Flashcards
What terminology is different between receptors and enzymes?
Receptors have ligands which can be agonists and antagonists while enzymes have substrates, products and inhibitors
What is the difference between a concentration-response curve and a dose-response curve
Concentration-response curve is used when there is an isolated system is immersed while a dose is the amount given to the whole organism
What is a saturation effect?
When increasing the concentration of the drug does not result in an increased effect, but does NOT require all agonists to be bound to receptors
What is Emax?
The maximum effect possible (saturation effect)
What is pD2?
A measure of agonist potency, a higher pD2 means a greater potency
What is EC50?
The effective concentration that produces 50% of the maximum effect, a lower EC50 means a greater potency
What is ED50?
The effective dose that produces the 50% of the maximum effect
What is the relationship between pD2 and EC50?
pD2=-logEC50
What shape is characteristic of concentration response curves?
Sigmoidal
What is IC50?
The concentration of an antagonist which inhibits half of the agonist response
What are the changes to an agonist concentration response curve in the presence of reversible and irreversible antagonists?
with a reversible antagonist the curve is right shifted (but not downwards shifted) with no effect on maximal responseWith an irreversible antagonist the curve is left shifted and will plateau out at a lower level
What is competitive reversible antagonism?
When the antagonist is reversible and competes directly with the agonist for the same binding site on the receptor resulting in a higher agonist concentration being required to produce the same effect
What is pA2?
-log (2*concentration that gives EC50), varies with different receptor and agonists is a measure of the potency of the antagonist
What is an example of a competitive reversible antagonist?
Propranolol at beta-2 receptors,Atropine at M
What is competitive irreversible antagonism?
An antagonist competes for the same binding site as the agonist but the antagonist has much greater affinity and can typically not be easily removed from the receptor and therefore not be overcome through increasing the amount of agonist