Lecture 36 - Drug receptor interactions

Question 1

receptors are

Answer 1

macromolecules involved in chemical signalling between and within cells
Cell activity changes once stimulated
Receptor must recognise the molecule and action has to happen

Question 2

Ligand

Answer 2

molecule that binds to site on receptor

Question 3

Receptor Occupancy

Answer 3

The fraction of the binding site occupied by the ligand

Question 4

Dissociation Constant (Kd)

Answer 4

Describes the affinity between a ligand and receptor site

smaller the kD, the more tightly bound the ligand

Question 5

Agonist

Answer 5

Drug that binds to receptors and initiates a cellular response

It has high affinity and efficacy

Question 6

Partial Agonists

Answer 6

act on the same receptor but do not produce the same maximal response

Question 7

Inverse Agonist

Answer 7

acts on the same receptor but produces an opposite effect

Question 8

Antagonist

Answer 8

Drug that binds to receptors but does not initiate a cellular response
has affinity but no efficacy

Question 9

Competitive Antagonist

Answer 9

• binds to the same site as the agonist but does not activate it

Question 10

Non-competitive Antagonist

Answer 10

binds to an allosteric site to prevent activation of the receptor

Question 11

chemical bonds in order of decreasing bond strength

Answer 11

covalent - ionic - H2 - hydrophobic

Question 12

Affinity

Answer 12

chemical force that causes drug to bind to the receptor site

Question 13

efficacy

Answer 13

on binding, extent of functional change imparted to a receptor

Question 14

potency

Answer 14

dose of a drug needed to produce a biological effect

Question 15

What is the mass-action relationship in drug-receptor interactions?

Answer 15

only one drug molecule occupies each receptor and binding is reversible
For a given drug the magnitude of the response is proportional to the fraction of total receptor sites occupied by drug molecules

graded and dose dependant

Question 16

What are the 4 different types of receptors

Answer 16

1. ligand gated channels
2. G -protein coupled receptors
3. enzyme - linked receptors
4. intracellular receptors

Question 17

what are ligand-gated ion channels?

Answer 17

A group of transmembrane ion channel proteins which open to allow ions to pass through the membrane in response to the binding of a ligand such as a neurotransmitter.
E.g. Glutamate, Serotonin, Dopmaine, Acetylcholine

Question 18

what are G-Protein-coupled receptors?

Answer 18

These receptors are linked to their responses by regulatory Guanosine Triphosphate (GTP)-binding proteins or G proteins
This complex induces conformational change in the G protein

Question 19

What are second messengers?

Answer 19

Allow signals conduction to be amplifies
eg. ATP, cAMP, PKA
Enzymes that produce second messengers include:
adenyl cylase – involved in activation of protein kinase
Phoplipase C – involved in production of inositol triphosphate (IPS3) and diacyglycerol (DAG)

Question 20

enzyme-linked Receptors

Answer 20

Activate cascades of intracellular signals

Most are receptor tyrosine-kinases and are activated by growth factors

Question 21

Intracellular Receptors

Answer 21

The receptor is entirely intracellular
Ligand must be lipid soluble
Primary targets are transcription factors
E.g. steroid hormones

Question 22

dose -response curves

Answer 22

drug conc vs response - normal curve

drug conc in log scale vs response - sigmoidal curve

Question 23

what is threshold

Answer 23

dose that
produces a
just-noticeable effect

Question 24

what is ed 50

Answer 24

dose that produces

50% of maximum response

Question 25

what is the ceiling of the curve

Answer 25

lowest dose that produces maximal effect