Session 9.2: Pharmodynamics - receptor theory Flashcards
do most drugs bind reversibly or irreversibly to receptors
mostly reversibly - associate then dissociate
binding obeys what law
law of mass action (binding related to concentration of reactants and products)
ligand + receptor
reversibly to form ligand-receptor complex
what must a ligand to bind to a receptor
affinity for its receptor
higher concentration of ligand = so higher affinity = stronger/higher binding
how is binding measured
measure binding of radioactively labelled ligand (radioligand) to intact cells or cell membranes. incubate and allow to come to equilibrium and measure bound radioligand
a single cell will have about
10000 or 100000 receptors
as concentration of drug increases
amount of drug bound to receptor increases (curve - sigmoidal plot/semi log plot)
what is Bmax
the max binding capacity - receptor number
which is found where curve levels out
what is the dissociation constant, Kd or KD
the concentration of drug that is required to occupy half the available receptors
draw line to curve and down
if Kd is lower
higher affinity
what is affinity
a measure of the strength with which a ligand or drug binds to a receptor
the likelihood of how well a ligand will optimally fit the receptor or target molecular binding site
how many receptors occupied per cell at certain kd
half the number of receptors present
how is the graph made into a log scale
converting the concentration into log units or plotting data on a log scale
log10 1000
= 3
ligand concentrations are usually
much lower than 1M
