Lecture 7

Question 1

What is the definition of pharmacology?

Answer 1

What drugs do and how they do it

Question 2

Describe briefly how a drug exerts its effect

Answer 2

Drugs bind to cellular targets, usually proteins but sometimes DNA. These interactions are specific. More specifically theses receptors are a super family of proteins.

Question 3

List some of the types of proteins involved in these interactions and give examples of some of the ligands that bind to them

Answer 3

Ligand-gated ion channels e.g. nicotinic acetylcholine receptor.
Receptors with intrinsic enzyme activity e.g. insulin receptors.
G-protein coupled reactors e.g. beta-adrenoceptors. Intracellular nuclear receptors e.g. glucocorticoid receptor.

Question 4

How do adrenoceptors interact with its ligand?

Answer 4

These receptors are what enable the fight or flight response. The endogenous ligand is adrenaline or noradrenaline.
Some exogenous or synthetic ligands that are used to create the same response are isoprenaline (which only interacts with beta-adrenal receptors) and salbutamol (beta 2 adrenal receptors). Propranolol binds to adrene receptors but doesn’t cause a response.

Question 5

What is ligand-receptor binding selectivity?

Answer 5

The lock and key mechanism is used to describe the relationship the ligand has to its receptor. The ligand has multiple interactions with receptor binding pockets, but these interactions are not covalent. Most interactions are reversible.

Question 6

What is the definition of a ligand?

Answer 6

It is a molecule/ ion that binds to a receptor. Its binding is governed by kinetics of association and dissociation.

Question 7

What is EC50 and how is it calculated?

Answer 7

EC50 is the effective concentration of ligand producing 50% of the maximal response. The concentration of the drug plotted as a logarithmic scale against % response gives a sinoidial curve. The maximum point reached is the Emax. Half the Emax corresponds to the concentration of EC50.

Question 8

What is the difference between antagonists and agonists?

Answer 8

Agonists possess both affinity and ability to cause intrinsic enzyme efficiency whereas antagonists have the affinity but cannot bring about a response.