Receptors and Basic Pharm

Question 1

Drugs exert their effect by…..

Answer 1

binding to a receptor (protein)

Question 2

Receptors act as a……..

Answer 2

signal transducer

when receptors bind a drug they send some sort of signal tot he cell machinery to produce a physiological effect

Question 3

agonists

Answer 3

drugs that actively produce a physiological effect

Question 4

antagonists

Answer 4

drugs that block the action of agonists

Question 5

a binding curve of a drug bound to a receptor vs free drug concentration looks like…..

Answer 5

a rectangular hyberbola

Question 6

having 100% of the receptor bound by drug is a limit approached as the drug concentrations gets….

Answer 6

very high

Question 7

define the dissociation constant describing drug binding to its receptor

Answer 7

the concentration of drug providing 1/2 maximal binding

Question 8

semilog plots (drug bound to receptor) vs log (free drug) provide….

Answer 8

sigmoidal curves that allow a more complete range of data to be shown.

Note: linear curves don’t allow such a large range of data to be plotted. Pharmacologists like to express data over a 1000 fold or more range of drug concentration. When plotted on a semilog plot the data goes from a rectangular hyperbola to a sigmoidal curve.

Question 9

most drugs function by interacting with?

Answer 9

receptor proteins and either facilitating (agonist drugs) or blocking (antagonist drugs) their function

Question 10

Pilocarpine……. salivation by the submaxillary gland and atropine…… this effect

Answer 10

stimulates salivation

blocks this effect

Question 11

pilocarpine and atropine product their effects by acting upon…..

Answer 11

muscarinic acetylcholine receptor proteins of the salivary glands

Question 12

muscarinic antagonists can produce…

Answer 12

xerostomia

Question 13

Summarize Langley’s experiment (the origin of the cell receptor theory)

Answer 13

Drugs A and B can bind to a receptor Y. They compete based on how much of each drug is present and how well each can bind to the receptor.

Note: this is true for competitive antagonists

Question 14

Langley concluded that cells have what 2 distinct things?

Answer 14

1. ) chief substance- concerned with carrying out the chief functions of the cells (contraction, secretion, formation of metabolic products etc.)
2. ) receptive substances- liable to change and capable of setting the chief substance into action

Question 15

nicotine is an….

Answer 15

agonist

Question 16

curare is an….

Answer 16

antagonist

Question 17

interaction of a drug with a receptor is based on the law of…

Answer 17

mass action

Question 18

describe the rate of association and dissociation relative to each other at equilibruim

Answer 18

they’re equal

Question 19

k1 [Lf] [R]

Answer 19

rate of association
R- receptor
Lf- free drug

Question 20

k-1 [RL]

Answer 20

rate of dissociation

Question 21

Kd

Answer 21

dissociation constant

[R] [L] / [RL] = Kd

Question 22

how to plot drug bound to receptor vs drug concentration
[RL] = ?
what is the shape of the graph?

Answer 22

[RL] = [Rt] [Lf] / (Kd + [Lf])

Rt- total receptors
Lf- free drug

rectangular hyperbola

Question 23

As Lf approaches infinity RL/Rt approaches?

Answer 23

it approaches 1

aka. once the drug concentration is high enough, basically all of the receptor will contain bound drug

Question 24

When RL / Rt = 1/2, Lf = ?

Answer 24

Lf = Kd
aka. the equilibrium dissociation constant (Kd) describes the drug concentration required for 1/2 maximal binding to occur

Question 25

Is it possible that two drugs L1 and L2 act at the same receptor site but require vastly different concentration to achieve the same effect?

Answer 25

Yes.
Drug binding depends how much drug is available for binding (concentration) as well as the dissociation constant Kd. If drug L1 has a higher Kd than drug L2, more of drug L1 will be required to achieve equivalent binding to L2.

Question 26

If X amount of drug produces a certain effect, will 2x the amount of drug produce roughly twice as much of an effect?

Answer 26

No, not necessarily. Probably not.
It depends on where you are on the binding curve. if the amount of drug bound to receptor is low, doubling the amount of drug will roughly double the amount of drug bound to the receptor which MAY double the effect. However if the amount of drug bound to the receptor is high, doubling the amount of drug will have little to no effect.