PL - Medicines

Question 1

What do medicines contain?

Answer 1

Pharmacophores.

Question 2

Certain chemicals fit into certain receptors in our cells but what do they do when they have temporarily bonded with each other?

Answer 2

The chemicals either inhibit them or trigger a series of biochemical reactions.

Question 3

What has to be right about the chemical if it is to fit into the receptor?

Answer 3

It needs to be exactly the right size and shape to fit the receptor, otherwise they don’t bond and nothing happens.

Question 4

What happens if a chemical isn’t the exact right shape and size to fit the receptor?

Answer 4

Then they don’t bond and nothing happens.

Question 5

What does molecular recognition describe?

Answer 5

The intermolecular interaction between two or more molecules.

Question 6

What describes the intermolecular interaction between two or more molecules?

Answer 6

Molecular recognition.

Question 7

What does a drug molecule have to have in order to be medicinally active?

Answer 7

The correct molecular recognition with a receptor.

Question 8

If a drug molecule has the correct molecular recognition with a receptor, it is said to be what?

Answer 8

Medicinally active.

Question 9

What is the part of the drug that fits into the receptor site and make it medicinally active?

Answer 9

The pharmacophore.

Question 10

What is a pharmocophore?

Answer 10

The part of the drug that fits into the receptor site and makes it medicinally active.

Question 11

What do chemists try to design drugs with?

Answer 11

Pharmacophores that fit exactly into target receptors in the body.

Question 12

What does the ‘fit’ of a pharmacophore into a receptor site depend on?

Answer 12

1) Size and shape.
2) Bond formation.
3) Orientation.

Question 13

How does the size and shape of a pharmacophore effect its ‘fit’ into a receptor site?

Answer 13

It’s got to have a particular structure that will fit into the receptor site.

Question 14

How does the bond formation of a pharmacophore effect its ‘fit’ into a receptor site?

Answer 14

Functional groups in the pharmacophore form temporary bonds with functional groups in the receptor. These are mostly ionic interactions or intermolecular forces. For example:

• Dipole-dipole interactions - these can form between the receptor and any polar functional groups in the pharmacophore.
• Hydrogen bonding - pharmacophores containing functional groups such as amines, alcohols and carboxylic acids may be able to form hydrogen bonds with the receptor site.
• Ionic interactions - acidic and basic functional groups can donate or accept protons to become charged and so form electrostatic attractions with the receptor site.

Question 15

How does the orientation of a pharmacophore effect its ‘fit’ into a receptor site?

Answer 15

If the pharmacophore has E/Z optical isomers, then only one of the isomers will fit.

Question 16

Where can dipole-dipole interactions form in relation to pharmacophores and receptors?

Answer 16

Between the receptor and any polar functional groups in the pharmacophore.

Question 17

Where can hydrogen bonds form in relation to pharmacophores and receptors?

Answer 17

Pharmacophores containing functional groups such as amines, alcohols and carboxylic acids may be able to form hydrogen bonds with the receptor site.

Question 18

Where can ionic interactions form in relation to pharmacophores and receptors?

Answer 18

Acidic and basic functional groups can donate or accept protons to become charged and so form electrostatic attractions with the receptor site.

Question 19

What does modifying the pharmacophore do?

Answer 19

Changes the pharmacological activity.

Question 20

Once you know that part of a molecule is a pharmacophore why can tweaking bits of it be beneficial?

Answer 20

As it can make a drug more effective or reduce its side effects.

Question 21

Give an example of how modifying a pharmacophore has been beneficial

Answer 21

Noradrenaline is found in the body and has been modified to treat different disorders. It expands airways and increases your heart rate and blood pressure.

It has been modified to make:

• Salbutamol which treats asthma symptoms, without the raised heart rate and blood pressure
• Isoprenaline which is used to increase heart rate for some heart problems.

(The pharmacophore has to stay the same or the drug won’t be active - different molecules and atoms are attached/bonded for different modifications.)