Drug receptor interactions

Question 1

How many of the top drugs on the market target G-protein coupled receptors?

Answer 1

34 of top 100

Question 2

What is an agonist drug?

Answer 2

drug that binds to a receptor and elicits a biological process

Question 3

What is an antagonist drug?

Answer 3

Drug that blocks the action of an agonist compound: commonly binding to a receptor without eliciting a biological response

Question 4

What is a partial agonist drug?

Answer 4

An agonist drug that produces a biological effect but never the maximal of which the tissue is capable-posses antagonist properties

Question 5

What is an inverse agonist drug?

Answer 5

Agonist that produces an opposing biological response to that observed by a full agonist

Question 6

What is affinity?

Answer 6

Ability of a drug molecule to bind to a receptor site

Question 7

What is efficacy?

Answer 7

Ability of a drug to elicit a biological response from a drug receptor interaction

Question 8

What is occupation governed by?

Answer 8

Affinity

Question 9

What is activation governed by?

Answer 9

Efficacy

Question 10

How do most agonists bind to receptors?

Answer 10

Reversibly

Question 11

Why do most agonist bind reversibly?

Answer 11

Relatively weak attractions such as Hydrogen bonding, ionic bonding and van der waal’s forces between the receptor and agonist, therefore easy dissociation

Question 12

How do some agonist bind to receptors in rare cases?

Answer 12

Irreversibly

Question 13

Why do agonist rarely bind irreversibly?

Answer 13

Interactions between receptor and agonist are by stable strong bonds such as covalent bonds. These are relatively strong therefore have poor dissociation

Question 14

What is the B-max?

Answer 14

Maximum amount of receptors the drug can bind to

Question 15

What is the Kd?

Answer 15

Amount of drug needed to occupy half the number of maximum receptor

Question 16

What is the relationship between kd and affinity?

Answer 16

The higher the Kd, the lower the affinity

Question 17

Does each drug have its own unique Kd value?

Answer 17

Yes, each drug has its own kd

Question 18

What is the law of mass action dependent on?

Answer 18

Dependent on the concentration of the reactants involved

Question 19

What is the law of mass action?

Answer 19

Rate of a chemical reaction is directly proportional to the product of the activities or concentrations of the reactants

Question 20

What are the predictions the law of mass makes?

Answer 20

Low[A]- Few AR interactions
Increase[A]- More AR interactions
Continue to increase[A]- Few Rfree, reaction reaches maximal

Question 21

The points on increase in biological affect against Log[A]

Answer 21

(a)Threshold concentration
(b)EC50=effective concentration giving 50% biological response
Used to compare drug potency
(c)Maximal concentration

Question 22

Why is the threshold concentration, EC50 and maximal concentration important values?

Answer 22

They’re important for determining drug doses

Question 23

Is affinity and efficacy equal?

Answer 23

No these values are not equal as full occupancy is not required to give a maximum response

Question 24

What do receptors do to signals?

Answer 24

Receptors amplify signals so only a small number of drug-receptor interactions produce biological effects

Question 25

Where are partial agonists present and what is there affinity and efficacy like?

Answer 25

Present at receptors-high affinity, low efficacy

Question 26

What do partial agonists reduce?

Answer 26

Reduce withdrawal effects
Reduce additive highs
Heroin-induced highs are reduced in the presence of partial agonist

Question 27

What do receptors only bind?

Answer 27

Receptors only bind agonists or antagonists

Question 28

What do agonist and antagonist do in competitive antagonism and how do they bind?

Answer 28

Agonist and Antagonist compete for same binding site

Agonist and antagonist both bind reversibly

Question 29

What is competitive antagonism dependent on?

Answer 29

Dependent on two equilibrium constants, KA and KAnt

Question 30

If Kantagonist

Answer 30

Agonist has greater affinity for receptors than agonist

Question 31

How can the binding of antagonist to receptors be overcome?

Answer 31

Increasing the concentration of agonist

Question 32

Reponse against Log[A[

Answer 32

• In presence of antagonistic concentration- effect of curve is shifted to the right
• Shift to right is linearly related to concentration of antagonist
• Linear part of the curve is parallel
• Same maximal response is obtained-if you increase concentration of agonist you will outcompete antagonist

Question 33

What happens during an overdose?

Answer 33

• Receptors overloaded and the pharmacological effect exceeds high
• This results in respiratory depression
• Eventually leading to death

Question 34

What is non-competitive antagonism and how does it work?

Answer 34

• Antagonist binds to a different site from the agonist
• Causes 3D shape of the receptor to change and this will therefore not allow agonists to bind
• Fewer number of receptors available for agonist to bind to
• This blocks the pharmacological effect

Question 35

What is irreversible antagonism and how does it work?

Answer 35

• Antagonist bind irreversibly to either agonist or non-agonist binding sites on receptors through covalent bonds
• Reduces number of receptors the agonist bind to
• There is still a pharmacological affect however the maximum response is reduced a lot compared to agonist alone

Question 36

How does asprin work to inhibit COX activity?

Answer 36

• Acetylsalicylic acid’s acetyl group forms an irreversible covalent bond with active site of enzyme
• This blocks the receptor site and inhibits COX activity.