Lectures 5-7

Question 1

What is EC50?

Answer 1

concentration giving 50% of the max effect.

often sigmoid curve in log graph.

Question 2

How do you describe the functional response of a system - equation.

Answer 2

E = Emax x [D] / EC50 + [D]

Question 3

Why is there not a 1:1 relationship between Kd and EC50?

Answer 3

function doesn’t equal occupancy. ie one receptor can activate 4 enzymes.

“spare receptors” not all needed.

Question 4

What is potency?

Answer 4

The concentration of a drug required to give a certain response.
EC50 often used.

A smaller EC50 = higher potency

Question 5

What is pEC50?

Answer 5

-log EC50

Question 6

What is a ligand?

Answer 6

a molecule that binds to something.

Question 7

What is a receptor?

Answer 7

Binds a ligand and transduces information.

Question 8

What is an agonist?

Answer 8

a ligand that binds to a receptor and activates it.

Question 9

What is capsaicin an agonist to?

Answer 9

VR1

Question 10

What is an antagonist?

Answer 10

binds but no transduction (like inhibitor).

Binds to same site, blocks it.

Question 11

What is transduction?

Answer 11

passing on information.

Question 12

What are the types of antagonism?

Answer 12

orthosteric (competitive)
allosteric (non-competitive)
functional
indirect

Question 13

Describe orthosteric antagonism.

Answer 13

competitive.
same site as agonist.
most common form.

Question 14

What does surmountable mean?

Answer 14

an increase in agonist can overcome the antagonist.

Question 15

What is the Gadam equation?

Answer 15

E = Emax x [D] / [D] + EC50 (1 + [B]/KB)

[B] = antagonist conc
KB = dissociation constant of antagonist.

Question 16

What is the concentration ratio?

Answer 16

1 + [B]/KB

can rearrange to get [B] = KB

Question 17

What is pA2?

Answer 17

• log KB causing 2 fold shift

- ->conc ratio = 2

Question 18

What is IC50?

Answer 18

inhibition curve.
fixed agonist, add varying antagonist conc.

inhibitory conc with 50% of starting response.

Question 19

What is selectivity?

Answer 19

relative potency/affinity at one receptor compared to another.

can be applied to agonist and antagonist.

Question 20

What is affinity and efficacy of a drug?

Answer 20

Affinity is how strongly it binds.
Efficacy is what it does once it binds to a receptor.

agonists have full efficacy.
antagonists have zero efficacy.
partial agonists have some efficacy.

Question 21

affinity and kd?

Answer 21

high affinity = low kd

Question 22

What are partial agonists?

Answer 22

partial efficacy.

Question 23

explain affinity.

Answer 23

full agonist has a high affinity for active state compared to inactive state.

partial agonist has high affinity for active state, but moderate affinity for inactive state.

antagonist has equal affinity for both states.

Question 24

what determines the heart rate?

Answer 24

atropine increases the heart rate by blocking mAChR.

???? lecture 7

Question 25

what is non competitive and un competitive antagonists?

Answer 25

allosteric - non competitive.
reduces max effect, unaffected by agonist concentration.

uncompetitive - requires agonist to activate receptor.
“use dependent”

Question 26

describe functional antagonists.

Answer 26

2 agonists have opposite effects on the same system.

total effect is the sum.

Question 27

What is indirect antagonism?

Answer 27

not very common.
agonist releases a chemical from one cell type which then acts on a second cell type.

if an antagonist prevents the effect of the chemical it appears as if it blocks it from the start.

Question 28

What is saturable?

Answer 28

max binding determined by no of sites

Question 29

what is rectangular hyperbola?

Answer 29

right angle shaped.

plot as log

Question 30

how do you measure affinity?

Answer 30

kd.

conc that gives 50% max occupancy.

Question 31

what is the equation for drug binding?

Answer 31

B = Bm x [D] / Kd + [D]

Bm = max binding
[D] = drug conc
Kd = conc for 50% max binding
B = drug bound