S1: Introduction to Receptors

Question 1

What is pharmacodynamics?

Answer 1

What the drug does to the body and its mechanism of action

Question 2

What is pharmacokinetic?

Answer 2

What the body does to the drug, how it is absorbed, distributes, metabolised and excreted

Question 3

What is a drug?

Answer 3

A drug is any chemical that has a biological effect

Question 4

Name the 3 characteristics of drugs

Answer 4

1. Drugs have a variety of effects/tissue selectivity
2. Chemical sensitivity
3. Drugs are very potent (high affinity and efficacy)

Question 5

Explain the chemical sensitivity of drugs

Answer 5

Small changes in structure can cause huge changes in bio activity

Example is that the enantiomer (+) for adrenaline produces about 100x greater biological effect the (-) enantiomer

Question 6

Explain the high potency of drugs

Answer 6

Drugs act in low concentrations

This is because receptors are able to amplify biological responses

Question 7

What is a receptor?

Answer 7

A receptor is a target molecule which physiological mediator (e.g. neurotransmitter) and ‘given’ drugs bind to, to produce a cellular response

Question 8

Name 3 general properties of receptors

Answer 8

1. They are expressed in different tissues which is why a drug can have effects on different tissue
2. They are highly selective targets which only specific structures bind to
3. They amplify signals, only small number of drug/receptor interactions needed to initiate significant biological effects

Question 9

In basic terms, what happens when a drug binds to a receptor (generally)

Answer 9

When the drug molecule binds, it will activate the receptor which causes a conformational change which may change a cellular process

Question 10

List the 4 types of receptors

Answer 10

Receptors
Enzymes
Carrier molecules
Ion channels

Question 11

Definition of an agonist

Answer 11

A drug which binds to a receptor to produce a biological cellular response

Question 12

Definition of a antagonist

Answer 12

A drug which binds to a receptor but does not produce a biological effect

They often bind to receptors to prevent agonists producing effects

Question 13

What are the 2 steps in drug action and what are they governed by?

Answer 13

1. Occupation which is a drug binding to receptor (governed by affinity)
2. Activation which is producing a response (governed by efficacy)

Question 14

What is affinity?

Answer 14

The degree to which a substance tends to combine with another

Question 15

What is efficacy?

Answer 15

The ability to produce a desired or intended result

Question 16

Does an agonist have affinity and efficacy?

Answer 16

Yes

An agonist will have affinity and occupy it to form a complex between receptor and agonist and then it will activate the receptor due to its efficacy producing a biological response

Question 17

Does a antagonist have affinity and efficacy?

Answer 17

No

An antagonist has affinity so will occupy it but it will not activate it due to no efficacy

Question 18

Which are the two main ways of classifying drugs?

Answer 18

1. According to their clinical use

2. According to target receptor

Question 19

How are receptors classified?

Answer 19

They are classified according to agonist and antagonists that act on the receptors

Question 20

What are the two types of adrenoreceptors?

Answer 20

Alpha and Beta

They are distinguished by the agonist and antagonist that act on them

Question 21

Why are some adrenoreceptors classified as alpha-adrenoreceptors

Answer 21

For some adrenoreceptors where noradrenaline is more potent than adrenaline which is more potent then isoprenaline

Question 22

Why are some adrenoreceptors classified as beta-adrenoreceptors

Answer 22

Isoprenaline is more potent than adrenaline which is more potent than noradrenaline

Question 23

What happens to alpha-adrenoreceptors in the blood vessels when stimulated?

Answer 23

Increase blood vessel constriction

Question 24

What happens to beta-adrenoreceptors in the heart when stimulated?

Answer 24

Stimulate heart rate

Question 25

What blocks alpha-adrenoreceptors?

Answer 25

Prazosin

Question 26

What blocks beta-adrenoreceptors?

Answer 26

Atenolol