Affinity and Capacity

Question 1

What is affinity?

Answer 1

How tightly the hormone binds

Question 2

What is capacity?

Answer 2

The receptor concentration

Question 3

True or false. The law of mass action is always reversable.

Answer 3

True

Question 4

What are the two conditions that law of mass action must follow to be at equilibrium?

Answer 4

1. Net concentrations of hormone, receptor and receptor binding do not change
2. Kon[R][H]=Koff[HR]

Question 5

What is formula for the dissociation constant?

Answer 5

Koff/Kon= Kd

Question 6

What does the dissociation constant measure?

Answer 6

The affinity of hormone to receptors

Question 7

What is the receptor’s affinity if Kd is high?

Answer 7

Low affinity

Question 8

What is the receptor’s affinity if Kd is low?

Answer 8

High affinity

Question 9

What is the name of the method to measure Kd experimentally?

Answer 9

Grind and Bind

Question 10

During “grind and bind,” what is constant and what varies?

Answer 10

The tissue amount must be constant and vary the amount of radiolabeled hormone

Question 11

Why must you quickly separate free and receptor bound hormone during grind and bind?

Answer 11

Because it was start to dissociate

Question 12

During bind and grind, what do you measure?

Answer 12

Amount of receptor-bound radiolabeled hormone

Question 13

On a graph with bind and grind, you have to find what?

Answer 13

Bmax

Question 14

What is Bmax?

Answer 14

The binding capacity

Question 15

Kd is what percentage of Bmax?

Answer 15

50%

Question 16

What is Kd?

Answer 16

The concentration of hormone needed to occupy 50% of present receptors at equilibrium

Question 17

True or false. Kd changes with the concentration of receptors.

Answer 17

False. Kd does not change with the concentration of receptors.