Receptors And Ion Channels Flashcards
What is the rINN name for the following drugs
a) butoxamine
b) clorgyline
c) amphetamine
a) butaxamine
b) clorgiline
c) amfetamine
What is 5-HT
5-hydroxytryptamine (serotonin)
Are steroid receptors membrane bound or cytosolic
They are cytosolic proteins
Give the five forces involved in the structure of a receptor in diminishing order of strength
Covalent bonds
Ionic bonds
Hydrogen bonds
Van der Waals Forces
Hydrophobic forces
How are large ligands believed to bind to receptors
Through a zipper interaction
Define agonist in terms of a receptor
An agonist binds to receptors and produces a response
Describe the approximate relationship between the size of the response and the concentration of agonist
What about when the response is plotted against the logarithm of the agonist concentration
Hyperbolic
Sigmoidal
What is the amount of a receptor that is bound by a given concentration of a drug governed by?
The affinity of the drug for the binding site
What is efficacy
The relationship between the amount of receptor occupied by a drug and the size of the response produced
True or false
An agonist has both affinity and efficacy
True
as they both binds to and activates a receptor to produce a response
True or false
Both antagonists and agonists display efficacy
False
both display affinity as antagonists bind but elicit no response
How is efficacy usually measured
What does this allow calculations of
On a log graph
EC50 - A measure of potency for agonists
What is EC 50
The concentration of the agonist that causes 50% of the maximum response
The response does NOT indicate the concentration of agonist occupying half of the receptors
What is potency
The concentration causing a particular magnitude of response (e.g. EC 50) - not to the size of the maximal response
What happens to the log concentration/response curve for an agonist in the presence of a competitive antagonist
It is shifted to the right in a parallel fashion
Can a maximal response be obtained if the agonist is in the presence of a competitive antagonist
Therefore what is another name of competitive antagonism
Yes, if enough agonist is added then the same maximal response is obtained
Surmountable antagonism
Does the addition of a competitive antagonist increase or decrease the EC 50
Increase
Maximal response remains the same
What is a structure activity series
A sequence of experiments to determine the relative potency of a group of structurally related compounds
What can be used to aid receptor classification
Give an example
In the case of ACh, two structure activity series can be seen and these help demonstrate the existence of two types of receptor, nicotinic and muscarinic receptors
Why can drugs with the same chemical formula offer different potencies
What does this demonstrate
Stereoisomers act differently
The complementarity of the interaction between drug and receptor
What is acetyl-β- methylcholine
What does its stereoisomer do
What does this mean for the racemate of acetyl-β-methylcholine?
Cholinergic agonist
Isomer has no affinity
Effectively reduces the concentration of the active isomer by half
What does isoprenaline do
What is the effect of its stereoisomer
What happens if you increase concentrations of the racemate
β- adrenoceptor agonist
Inactive isomer has affinity but no efficacy so acts as an antagonist
Simultaneously increases [agonist] and [antagonist]
What is the forward and backward reactions of the following know as:
D+R↔️DR
What does the rate of each equal?
Forward: K+1; rate =K+1[D][R]
Backwards: K-1; rate = K-1[DR]
What is the notation for the affinity constant of drug D
Ka (=k+1/k-1)