Question

1. Osmotic Pressure:

1. You are trying to make artificial blood cells. You have managed to get pure lipids to form spherical bags (cells) of radius 10 μm, filled with hemoglobin. The first time you did this, you transferred the cells into pure water and they promptly burst, spilling the contents. Eventually you found that transferring them into a 1 mM salt solution prevents bursting, leaving the cell spherical and full of hemoglobin and water.

1. Explain the reason why the cells burst when you transferred them into pure water.
2. If 1 mM is good, then would 2 mM be twice as good? What do you think would happen if you try this? Explain.
3. Later you decide that you don’t want salt outside because it makes your solution electrically conducting due to the dissociation of salts solution. Therefore, you decided to use glucose solution instead. How many moles per liter (M solution) of glucose you should try?

2. The osmotic pressure of blood plasma proteins is usually expressed as about 28 mm of mercury (760 mm of mercury ≈ 1.01 x 10⁵ Pa) at body temperature of 37 ˚C.

1. Estimate the concentration of plasma proteins (in mM).
2. If the quantity of plasma protein present has been measured to be about 60 g/L, estimate the average molar mass (in g/mol) for these plasma proteins, assuming the validity of the dilute limit.

Answer 1

Ans A: The osmosis is process of movement of solute from lesser concentration to higher concentration across the semipermiable membrane and osmotic pressure is a minimum required pressure to prevent the osmosis process.

a. In this situation, when cells are transferred to the pure water, the cells burst because the osmotic pressure difference between water and artificial cell.

b. In this situation, when cells are placed in 1mM salt solution the cells are stable because of the balanced osmotic pressure.

If we add same cells in a higher salt concentration solution (2mM) then cells may burst due to the salt solution causes increase in osmotic pressure

c. To calculte osmotic pressure the van hoff factor is considered.

The van hoff factor of glucose is 1 and if we consider salt is an NaCl, The van hoff factor of Nacl is 2.

So, to equalize the osmotic pressure we need doubled concentration of glucose as compared to salt

Thats why we require 2mM of glucose solution to replace the salt.