Ligands Flashcards
what are ligands
ligands are chemical messengers that bind to receptors to elicit a certain response
what is drug specificity
drug specificity means that a molecule can bind and will only bind to a specific target
what is drug selectivity
drug specificity is where a ligand binds PREFERABLY to a single target but can still bind to others
two types of ligands
endogenous ligands {neurotransmitters, hormones , atutocoids) and exogenous ligands ( drugs, poisons, toxins)
what is drug potency
is it the concentration needed of the drug to elicit 50% of the response
what is EC50
it is the effective concentration needed order to elicit 50% of the response
drug a and drug b is taken in two different people, drug elicits 75% of the the response at a lower concentration than drug b. drug b elicits 100% of the response however at a higher concentration. which drug has a higher potency and which drug has a higher efficacy
drug a has a higher potency because less concentration of the drug is needed to elicit 50% of the response, meaning the ligand has a higher affinity to its receptors. drug a has a lower efficacy because the activity compared to drug b is lower drug b has a lower potency because there is more concentration needed to elicit 50% of the response however drug b has a higher efficacy because more activity is happening.
as we move from the left to right on tehe x axis is potency increasing or decreasing and is the efficacy decreasing or increasing
the drug potency decreases and the drug efficacy increases
what do the units means on the x axis of this graph
it means the miiligrams (mg) of drug taken by the weight (kg) of the person
what are agonists
drugs that interact with, stimulate or activate receptos, it can not just bind to the receptors it needs to trigger a response and elicit a change in a biological pathway or system
mimics the action of the endogenous molcule
has the affinity for the receptors and has the efficacy once bound to trigger the response
what is clarks occupation theory or the classsical recpetor occupancy theory
measures how often a ligand is going to bind to the recpetor because the interation between the ligand and receptor is not constant. once a ligand is bound it will also unbind.
explain this equation
L is the ligand or the drug
R is the receptor
LR is the ligand-receptor complex
K+1 is the association rate constant aka Ka
K-1 is the disassociation rate constant aka Kd
how do we measure the proportion of receptors occupied
Pa is the proportion of receptors occupied
XA is the concentration of the ligand
KD is the equilibrium dissociation constant which is K-1/K+1
how can affinity be expressed as a a ratio and what does this ration mean
it it is expressed as K-1/K+1 and this means that this concentration of the drug is needed to occupt 50% of the RECEPTORS
what is the thrshold in a does-rsponse curve
the amount of dose that produces a just- noticeable effect
what is ED 50
effective dose that produces 50% of response
what is the difference between dose and concentraton
dose is something you give to a living entity like a human or a dog whereas cocentration is something to use in a experiment eg adding concentration of something to a culture of cells
describe how a does-response curve looks like
is the repsonse you get proportional to receptor occupancy ?
is the EC50 = affinity
50% of the response = 50% receptor ocupancy
no becauase we have partial agonists
what are partial agonists
are those which induce partial effects
similarites and differences between fulll agonists and partial agonists
full agonits induce full affect partila agonists have a partial effect
a full agonist has a high efficacy and can produce a full response while occcupying a low propportion of receptors
a partila agonist has alower efficacy, and not matter how high th does it cann produce a full response
both have an affinity fot receptors,
why can fulll agonists have a higher efficacy than partial agonists when both agonists have affinity for the same receptors
a full agonists, when bound, induces a larger shape change in the receptors than a partial agonist would
a larger change shape induces a stronger signalling pathway and a maximal response
a smaller change shaper induces a weaker signallling pathway and a submaximal reponse
what are inverse agonists
binds to the same receptors as a full agonist but induces a pharmacological response opposite to that of the agonist
what is desensitation and tachyplhylaxis
the loss of drugg effect over time
it can be the gradula tolerance to that the drug
or
some drugs dont work for example antimicirobial resistnace to drugs
also
mechanisms can cause this also, change in receptors, loss of receptors this can happen when the body notices that the body is getting overstiulated by a drug, exhaustion of mediators, active extrusion and physiological adapation: the body will stimulate more to counteract what the drug is trying to inhibit
what are competitive antagonists and non-competive antagonists
antagonists can bind to the smae site as an agonist but this binidng can be reversible whereas a non-competitive antagonist binds to the same site as an agonist but will do so irreversibly
competitive antagonists have no efficacy no its own
what are allosteric antagonists
what is IC50
inhibitory concentration which reduces the effect by 50%
wht happens to the dose resonse curve when you add antagonists
the curve shifts to the right therfore you need a higher does to get the same effect
