Lecture 4

Question 1

Explain osmotic pressure in terms of concentration of solute.

Answer 1

Higher the conc of solute, the larger the osmotic pressure.

Question 2

Equation for osmotic pressure

Answer 2

Van’t Hoff equation

ㅠ = nRTC

Question 3

What is the purpose of osmotic coefficient (phi) added to Van’t Hoff equation?

Answer 3

In concentrated solution, ions doesn’t complete dissociate. So osmotic coefficient measure of how well a solute in solution dissociates.
0-1 ; 1=complete dissociation

Question 4

What does Fick’s Law of Diffusion for water tell about the relationship between concentration gradient and net flux?

Answer 4

Bigger the concentration gradient, bigger the flux.

Question 5

what does theta mean in Fick’s law of diffusion for water?

Answer 5

reflection coefficient of solute

Question 6

what does theta = 0 mean in Fick’s Law of diffusion for water?

Answer 6

the solute is not reflected thus totally permeable.

Question 7

When theta = 0, is there flux of water between two compartments

Answer 7

No, there is no net water flux, because solute can penetrate.

Question 8

When theta = 1, is there flux of water between two compartments?

Answer 8

Yes, water will move to higher concentrated solution, which leads to increased volume in that compartment.

Question 9

When solute is penetratable, solution is isotonic, because there is no water movement, but to be more accurate, there is shrinkage of cell in the beginning then returns to isotonic shape. Why?

Answer 9

Its because the solute penetrates slower than water. So in the beginning, intracellular fluid is hyposmolar so water moves out of the cell to hyperosmolar solution. As a result cell shrink, but urea slowly moves into the cell, as a result, water returns into the cell, becoming isotonic.