L4: Drug Action at Receptors

Question 1

What are receptors?

Answer 1

Protein macromolecules that are inserted across lipid bilayer of cell

Question 2

2 main functions of receptors

Answer 2

1) Recognition/detection of extracellular molecules
2) Transduction

Question 3

What is transduction?

Answer 3

Detect the presence of an extracellular membrane, then bring changes in cell activity

Question 4

How do receptors interact with/ bind to with certain chemicals?

Answer 4

High degree of specificity

Question 5

How are receptors named/classified?

Answer 5

With respect to the drugs they bind

Question 6

Name given to any chemicals that bind to receptors

Answer 6

Ligands

Question 7

Equation of binding of drug (D) to receptor (R)

Answer 7

D + R ⇄ DR

Question 8

Whats the shape of a plot of proportion of receptors occupied vs drug concentration?

Answer 8

Rectangular hyperbola

Question 9

What is the plot of proportion of receptors occupied (p) vs log (D)?

Answer 9

Symmetrical sigmoid

Question 10

Define affinity of a drug for its receptor (KD)

Answer 10

Molar concentration of drug required to occupy 50% of the receptors at equilibrium

Question 11

How is the concentration of drug given as?

Answer 11

KD

Question 12

Is the KD high or low if a drug has a high affinity?

Answer 12

LOW

Question 13

Equation for rate of FORWARD reaction

Answer 13

k+1 (D)(R)

Question 14

Equation for rate of BACKWARD rate

Answer 14

k-1 (D)(R)

Question 15

What is KD a measure of?

Answer 15

A measure of how tightly the receptor holds onto the drug once they come together

Question 16

What is the KD?

Answer 16

Equilibrium Dissociation Constant

Question 17

What is an agonist?

Answer 17

Substance that binds & active the receptor, then produce a conformational change in the shape of the receptor to lead a response in a cell/tissue

Question 18

What is efficacy?

Answer 18

Ability of a drug to activate the receptor

Question 19

What is affinity?

Answer 19

Strength of drug binding with receptor

Question 20

What are the 2 types of agonist?

Answer 20

Full & Partial

Question 21

What is a full agonist?

Answer 21

High efficacy; effective at activating receptors

Question 22

What is the response of a full agonist?

Answer 22

Maximal response whilst activating a fraction of available receptors

Question 23

What is a partial agonist?

Answer 23

Low efficacy; less effective at activating receptors

Question 24

What is the response of a partial agonist?

Answer 24

Fail to produce full response despite occupying all available receptors

Question 25

How is the overall response of an agonist determined by?

Answer 25

Affinity & Efficacy

Question 26

What do we call drugs that show both affinity & efficacy at receptors?

Answer 26

Agonist

Question 27

Why is the EC50 for an agonist drug not always the same?

Answer 27

Determined by affinity & efficacy

Question 28

What is an antagonist?

Answer 28

A drug that stops the action or effect of another substance

Question 29

3 forms of antagonism

Answer 29

Chemical, Pharmacokinetic, Physiological

Question 30

What happens in chemical antagonism?

Answer 30

A drug combines with another to form an inactive product

Question 31

What happens in pharmacokinetic antagonism?

Answer 31

Decrease another drug's concentration at the site of action

Question 32

What happens in physiological antagonism?

Answer 32

2 drugs act to produce opposing effects, so they cancel each other out

Question 33

Which forms of antagonists does not act at the receptor?

Answer 33

Chemical, Pharmacokinetic and Physiological

Question 34

Which forms of antagonists act at the receptor?

Answer 34

Competitive & Non-Competitive

Question 35

What are competitive antagonists?

Answer 35

Compete with agonist for the same site on the receptor molecule, but don't activate it

Question 36

What are non-competitive antagonists?

Answer 36

Act at a different site on the receptor closely associated with it

Question 37

What are reversible competitive antagonists?

Answer 37

Used to inhibit the effects of a neurotransmitter/hormone

Question 38

How can reversible competitive antagonists inhibitory effects be overcome?

Answer 38

Increasing concentration of the AGONIST

Question 39

What happens to the graph for reversible competitive antagonists?

Answer 39

Parallel shift to the right of the AGONIST

Question 40

What are x & y axis on the reversible competitive antagonists graph?

Answer 40

x: log concentration of (agonist) y: response

Question 41

What happens to the line in the presence of an antagonist?

Answer 41

Shifts to the right

Question 42

What happens to the shift in a IRREVERSIBLE competitive antagonist graph?

Answer 42

Shift is not parallel, inhibition they produce is not overcome by increasing agonist concentration