Law of Mass Action

Question 1

The law of mass action was postulated by who and in what year?

Answer 1

CM Guldberg and P Waage in 1864

Question 2

State the law of mass action

Answer 2

The rate of reaction is directly proportional to the product of the active mass (concentration) of the reactants.

Question 3

At equlibrium, all receptors are equally accessible to ligands. T or F?

Answer 3

True

Question 4

At equilibrium, the receptor ligand binding is reversible. T or F?

Answer 4

True

Question 5

At equilibrium, all receptors are either free or bound to ligand; there is no more than one affinity state or states of partial binding. T or F?

Answer 5

True

Question 8

At equilibrium, binding does not alter the ligand or receptor. T or F?

Answer 8

True

Question 8

Following LMA, drugs combine with their receptors at a rate dependent on the conc. of the drugs and conc. of the receptors. T or F?

Answer 8

True

Question 9

Types of Labeled LBA?

Answer 9

1. Flourescent
2. Radioligand BA
3. Bioluminescent BA using nanoluciferase
4. Selenium labeling of peptide ligands

Question 9

What is the importance of ligand binding assays

Answer 9

To quantify drug-receptor interactions

Question 9

What is a ligand binding assay?

Answer 9

It is an analytical procedure that measures binding of ligands to receptors and other molecules.

Question 9

What is the purpose of radioactivity in LBA?

Answer 9

As a detection method to measure amount of ligand

Question 10

What are the types of LBA?

Answer 10

1. Labeled LBA
2. Label-free LBA
3. Structure-based LBA
4. Thermodynamic BA
5. Whole cell LBA

Question 11

Types of label-free LBA?

Answer 11

1. Surface plasmon resonance
2. Plasmon waveguide resonance
3. Whispering gallery micro resonator
4. Resonant waveguide grating
5. Mass spectrometry

Question 12

Types of structure based LBA?

Answer 12

1. NMR
2. X-ray crystallography

Question 13

Types of thermodynamic binding assays?

Answer 13

1. Thermal denaturation assays
2. Isothermal titration calorimetry

Question 14

Types of whole cell LBA

Answer 14

Surface acoustic wave biosensor

Question 15

What is a radioligand?

Answer 15

A radioactively labeled ligand that can bind with any target of interest e.g receptors

Question 16

What is the importance of RLBA?

Answer 16

1. Allows for the determination of the rate and extent of binding interactions.
2. Gives information on no of binding sites, affinity and accessibility of various drugs

Question 17

The equilibrium dissociation constant(Kd) is a measure of?

Answer 17

The stability of the L-R complex

Question 18

Kd is the inverse measure of?

Answer 18

Affinity

Question 19

A high-affinity drug has a ___ Kd

Answer 19

Low.

Question 20

A high-affinity drug will bind to a greater no of its receptor at a lower conc. T or F?

Answer 20

True

Question 21

When 50% of the receptors are occupied, the conc. of free receptors will equal that of bound receptors. T or F?

Answer 21

True

Question 22

At 50% occupation, [Ligand] = Kd. True or False?

Answer 22

True

Question 23

What is Kd?

Answer 23

The concentration of ligand at equilibrium that is required to occupy half the receptors

Question 24

T or F For an isolated, simple receptor system of the type R + l = R.L, Kd for ligand binding is that [ligand] at which max binding is observed.

Answer 24

False

Question 25

T or F For an isolated, simple receptor system of the type R + l = R.L, Kd for ligand binding is the equilibrium constant for R.L formation

Answer 25

False. It is the equilibrium dissociation constant

Question 26

T or F For an isolated, simple receptor system of the type R + l = R.L, Kd for ligand binding has units of per M

Answer 26

F. Unit is M

Question 27

T or F For an isolated, simple receptor system of the type R + l = R.L, Kd for ligand binding is a second order rate constant

Answer 27

False

Question 28

T or F For an isolated, simple receptor system of the type R + l = R.L, Kd for ligand binding is that [ligand] at which 1/2 of the receptor exists R.L

Answer 28

True

Question 29

What is the formula for fractional occupancy?

Answer 29

[Ligand]/[Ligand + Kd]

Question 29

Receptor fractional occupancy is?

Answer 29

The proportion of the receptors that are bound to or occupied by the drug.

Question 30

Who postulated the receptor occupancy theory?

Answer 30

Clark

Question 30

State the receptor occupancy theory?

Answer 30

The fraction of the receptor bound is directly proportional to tissue response

Question 30

What are the limitations of the receptor occupancy theory?

Answer 30

1. The slope of the conc.-response curves for certain drugs were steeper than predicatable by FO equation. 2. Extremely high conc. of certain other drugs failed to produce maximum response.