Introduction to Pharmacology

Question 1

What are the four types of receptors?

Answer 1

Ligand-gated ion channels, G-protein coupled receptors, kinase-linked receptors and nuclear receptors.

Question 2

What is the difference between endogenous and exogenous ligands?

Answer 2

Endogenous ligands are made within the body, exogenous ligands come from an external source.

Question 3

True or false? Antagonists activate receptors.

Answer 3

False. Agonists activate receptors.

Question 4

How do antagonists work?

Answer 4

Antagonists block an agonist ligand from binding to the receptor, preventing response BUT having no effect on the receptor itself.

Question 5

What is the difference between the functional site and the binding site?

Answer 5

The functional site is where the response to the ligand binding to the cell is produced. The binding site is where the ligand binds to the cell.

Question 6

Define specific ligand.

Answer 6

Specific ligands bind to only one type of receptor.

Question 7

Define selective ligand.

Answer 7

Selective ligands can bind to more than one type of receptor. This is because of similarities in the molecular structure of ligands.

Question 8

What is the potency of an agonist?

Answer 8

The amount of an agonist required to induce a response, expressed as a dose or a concentration.

Question 9

Does a high potency agonist require a higher or lower dose than a low potency agonist to induce an effect?

Answer 9

A high potency agonist requires a lower dose to induce an effect.

Question 10

What is the affinity of a ligand?

Answer 10

How well the ligand binds to a receptor.

Question 11

What is the efficacy of a ligand?

Answer 11

How effective a ligand is in activating a response. This only applies to agonists (because antagonists only block the binding of agonists, they do not activate responses themselves).

Question 12

The effect a ligand has on a cell is proportional to the number of …………occupied.

Answer 12

Receptors.

Question 13

Is the binding of endogenous agents and drugs to receptors reversible?

Answer 13

Yes. The exception is poisons!

Question 14

What three bonds / interactions determine the strength of ligand-receptor reactions? What type of bond is NEVER involved in ligand-receptor reactions?

Answer 14

1. Electrical charge interactions.
2. Hydrogen bonding.
3. Hydrophobic interactions.

Ligand-receptor reactions NEVER involve covalent bonding.

Question 15

Receptors follow the law of mass action, which states…

Answer 15

…‘the rate of a chemical reaction is proportional to the product of concentrations of reactants’.

Concentation of drug + concentration of receptor = concentration of drug/receptor complex.

Question 16

What is the difference between acute drug treatment and chronic drug treatment?

Answer 16

Acute drug treatment is a single treatment which induces an immediate response, due to direct action of the drug on a receptor.

Chronic drug treatment is repeated treatment that induces a delayed response due to indirect action on a receptor.

Question 17

What is a free agonist?

Answer 17

An agonist that is not bound to a receptor.

Question 18

Why can chronic drug treatment lead to tolerance?

Answer 18

Homeostasis acts to try an minimise the effect of the drug on cells.

Agonists - receptor downregulation / receptor desensitisation.
Antagonists - receptor upregulation / receptor supersensitivity.

Question 19

How fast do ligand-gated ion channels mediate transmission? And where?

Answer 19

Very fast transmission. In the nervous system, between neurons or at neuromuscular junctions.

Question 20

What are the ions that travel in and out of cells via ion channels?

Answer 20

K+, Na+, Ca+ and Cl-.

Question 21

What does cation-specific and anion-specific refer to, in terms of ion channels?

Answer 21

Cation-specific ion channels are only for positively charged ions. Anion-specific ion channels are only for negatively charged ions.

Question 22

Ionotropic receptors is another term for what?

Answer 22

Ligand-gated ion channels.

Question 23

Metabotropic receptors is another term for what?

Answer 23

G-protein coupled receptors.

Question 24

Which is the most abundant receptor type in the body?

Answer 24

G-protein coupled receptors.

Question 25

How fast are transmissions mediated by g-protein coupled receptors? Where do they take place?

Answer 25

Fast synaptic transmissions.

Question 26

When an agonist binds to a g-protein coupled receptor, does the receptor induce a response directly?

Answer 26

No. The response is induced indirectly through the g-protein. The receptor itself does not have any functional activity.