Basics: Definitions Flashcards
What is a ligand?
A substance that binds to proteins
What is affinity?
The tendency of a ligand to bind to its receptor
What is efficacy?
The tendency of a ligand to activate its receptor once bound
Why isn’t efficacy directly affected by affinity?
Because signals can be amplified
What is potency?
The activity of a drug, in terms of the concentration required to produce a specific effect
If EC50 is a smaller value, what is the potency?
Greater potency
What is an agonist?
A ligand that binds to a receptor and ilicits a biological response by mimicking the endogenous compound
What is an agonist?
A ligand that binds to a receptor and ilicits a biological response by mimicking an endogenous compound
What is difference between full and partial agonists?
They have similar affinities but full agonists have a much greater efficacy than partial agonists
What is an antagonist?
A ligand that binds to a receptor and reduces the action of another drug by acting on the same receptor or changing the conformation of the receptor via another binding site
What is KA?
Equilibrium constant, the concentration of a ligand required to occupy 50% of the receptors
What is IC50?
The concentration of an inhibitor required to inhibit 50% of the biological process
What is Ki?
The concentration of inhibitory drug required to occupy 50% of its receptors
What is used to determine how likely a drug is to bind to off targets
PKi (the higher the pKi, the more likely it is to bind to a certain receptor)
What is the two-state model?
The theory that a ligand must both bind to and activate its receptor (the first being affinity and the second being efficacy)
