Pharmacology receptors

Question 1

define receptor

Answer 1

macromolecule component of the cell which interacts with a drug to produce its characteristic effects

Question 2

what does Kd measure and what is it

Answer 2

drug affinity for its receptor
an equilibrium dissociation constant

Question 3

difference between an agonist and antagonist

Answer 3

agonist - cause conformational change to the receptor
antagonist - do not cause conformational changes

Question 4

how much of the total drug do you assume is bound

Answer 4

a negligible amount

Question 5

at equilibrium the rate of the reverse reaction is equal to what

Answer 5

the rate of the forward reaction

Question 6

what is Rt

Answer 6

total number of receptors

Question 7

what is D, DR and r

Answer 7

D - total drug concentration
DR - concentration of bound drug
r - fractional occupancy of the receptors

Question 8

how do you calculate r

Answer 8

DR/Rt

Question 9

how do you calculate Kd

Answer 9

[D][R]/[DR]

Question 10

what will a plot of r against [D] produce

Answer 10

a rectangular hyperbola curve

Question 11

what will a plot of r against log[D] produce

Answer 11

a sigmoidal curve

Question 12

what is occupation theory

Answer 12

Response[E] = number of receptors occupied

Question 13

what is pD2

Answer 13

negative log of the agonist concentration that gives half the maximal response

Question 14

what is a limitation of the occupation theory in terms of pD2

Answer 14

overestimates the Kd in some receptor systems
drug appears to bind more tightly than it actually does

Question 15

what is an antagonists ability to block receptors based on

Answer 15

affinity for the receptor
relative concentration of [A] to [D]

Question 16

define dose ratio

Answer 16

the ratio of the agonist concentration that elicits the same response either in the absence [D0] or in the presence of an antagonist [Da]

Question 17

what does it mean if the response is the same in the absence and presence of an antagonist

Answer 17

the occupancy of the agonist is the same irrespective if there are spare receptors

Question 18

how do you calculate the dose ratio from a dose-response curve

Answer 18

determine the agonist concentration at 50% for each curve
then divide the curves with antagonist present by the one in absence of antagonist
i.e. [D1]/[D0], [D2]/[D0]

Question 19

what is an assumption made for the dose ratio

Answer 19

based on law of mass action
assumes simple competitive antagonism

Question 20

what is Gaddum-Schild equation independent of

Answer 20

independent of the agonist used
as long as it competes for the same receptor as the antagonist

Question 21

there are no assumptions about what in the Gaddum-Schild equation

Answer 21

relationship between response and number of receptors occupied

Question 22

if the dose ratio is 2 what is the Ka and -logKa

Answer 22

Ka = A2
-logKa = pA2

Question 23

what is pA2

Answer 23

the negative log of the antagonist concentration that gives a dose ratio of 2

Question 24

if the slope on a logarithmic graph of log(dose ratio) - 1 (y-axis) and log[A] (x-axis) is equal to one what does this indicate about the type of antagonist

Answer 24

its competitive

Question 25

the drug-receptor interaction is rapidly reversible is an assumption of what theory

Answer 25

occupancy theory

Question 26

what are two assumption of the occupancy theory

Answer 26

all agonists for a given receptor can produce the same maximal response
the maximal response occurs when all the receptors are occupied
(these assumptions are low-key dog)

Question 27

all agonists for a given receptor produce the same maximal response, what is the problem with this assumption

Answer 27

some agonist drugs act on a receptor and produce a weak response - partial agonist

Question 28

what can partial agonists act as

Answer 28

competitive antagonists to full agonists

Question 29

what does a (alpha) mean

Answer 29

the ability of a drug to induce an effect - intrinsic activity

Question 30

what would the a for a partial antagonist be

Answer 30

<1

Question 31

what is the difference between a full agonist with high and low efficacy

Answer 31

high efficacy - needs to occupy a smaller amount of receptors to induce maximal response
low efficacy - need to occupy a larger amount of receptors to achieve maximal response

Question 32

what are 2 modification to the occupancy theory to account for partial agonists

Answer 32

effect depends on the affinity of the drug for its receptor
effect depends on the drugs ability to induce a conformational change in the receptor

Question 33

what is constitutive activity

Answer 33

some receptors have some activity during their resting state

Question 34

what is an inverse agonist

Answer 34

reverses constitutive activity, decreasing basal activity