THermo 2

Question 1

Define the equilibrium constant.

Answer 1

K eq = concentration of product / concentration of reactants;

the concentrations are at equilibrium.

Question 2

How to calculate K part in the free energy of transfer?

Answer 2

k part = M oct / M aq

Question 3

What value is associated with biological activity of a drug?

Answer 3

log K part;

= log P

Question 4

What are the ranges for log P?

Answer 4

• optimal log P for oral/intestinal absorption is ~1.3 - 1.8.
• Most orally taken drugs have 0 < log P < 3.
• very high log P leads to toxic build-up in fatty tissues;
• very low log P leads to low absorption

Question 5

What are the two constants in protein-ligand binding?

Answer 5

association: K a;
dissociation: K b.
(product over reactant)

Question 6

How to calculate what fraction of protein have drug bound?

Answer 6

% drug bound = Y

Y = [PL] / ([P] +[PL]) = [L] / Kd + [L]

Question 7

What are the two constants in Acid-Base Equilibrium? How are they connected?

Answer 7

Ka Kb = Kw

pKa + pKb = 14

Question 8

What is the neutral form for weak acids?

Answer 8

A- is charged form, HA is neutral form.

Question 9

What is neutral form for weak bases?

Answer 9

B - neutral form;

bH+ - charged form

Question 10

What does the hydrophilic group do?

Answer 10

It is polar/charged; it has specific interactions with proteins.