Receptors

Question 1

What properties are receptors defined by?

Answer 1

recognition and transduction

Question 2

Recognition:

Answer 2

Receptors bind reversibly with high affinity

Question 3

Transduction:

Answer 3

Structure-dependent conversion of binding into a cellular response –> activity of efficacy

Question 4

Are receptors the same as enzymes?

Answer 4

No

Question 5

How are receptors and enzymes different?

Answer 5

Ligands are not changed during binding to the receptor

Question 6

What is required for receptor binding interaction

Answer 6

Specificity
Saturability
Reversability

Question 7

Specificity:

Answer 7

Ligand is structurally complementary to receptor, specific and high affinity interaction

Question 8

Saturability:

Answer 8

A finite number of receptors per cell are present

Question 9

Reversibility

Answer 9

After binding, the ligand must dissociate in an unchanged form

Question 10

Low affinity –> Kd

Answer 10

Low

Question 11

High affinity –> Kd

Answer 11

High

Question 12

What is a saturation isotherm

Answer 12

The concentration of bound ligand plotted against the concentration of free ligand
The concentration of free ligands when 50% binding sites are used = Kd

Question 13

Ligands that bind to a receptor at the same site have what kind of inhibition

Answer 13

Competitive

Question 14

What is the effect of a competitive inhibitor

Answer 14

Decreases the apparent affinity of ligand, no effect on maximum binding at saturation

Question 15

What is the classical receptor theory

Answer 15

Response directly related to receptor occupation

Question 16

What is the modified classical theory?

Answer 16

The response can occur at lower concentrations of ligands than expected
Amplification of the signal can lead to spare receptors

Question 17

What is an agonist

Answer 17

A ligand that binds to a receptor and produces a response

Question 18

What is a partial agonist

Answer 18

A ligand that binds to a receptor and produces less than the maximum response

Question 19

How is efficacy measured

Answer 19

The response - conversion to activated state

Question 20

How is potency measured

Answer 20

The binding of the ligand and receptor

Question 21

What are competitive antagonist

Answer 21

Ligands that bind to the receptor at the same site as the agonist but do not result in activation

Question 22

What are noncompetitive antagonist

Answer 22

Ligands that bind to the receptor at a different site than the agonists and prevent activation

Question 23

Which is more common - competitive or noncompetitive antagonist

Answer 23

Competitive

Question 24

What do competitive antagonists do to efficacy and potency

Answer 24

Potency is decreased, efficacy is unchanged

Question 25

What do noncompetitive antagonists do to efficacy and potency

Answer 25

Decreases max response without affecting potency

Question 26

How do receptors desensitize themselves

Answer 26

Slow conformational change
Phosphorylation to inactive state
Binding to an inhibitory protein

Question 27

What are the ways receptors respond to excess varying amounts of ligands

Answer 27

Desensitization
Downregulation
Upregulation

Question 28

How does downregulation work

Answer 28

Endocytosis used for temporary sequestration or degradation of receptor

Question 29

When does upregulation occur

Answer 29

When there is prolonged exposure to antagonists

Question 30

How does upregulation work

Answer 30

Cells increase the number of receptors they express