Question

B. Molecular size:

What is the initial osmotic gradient when the RBC’s are placed in 300 mM methanol? What molecules contribute to the osmolarity of the cytoplasm? of the surrounding solution? Does the osmotic gradient change over time as the RBC’s remain in the 300 mM methanol solution? In this scenario, which molecules are moving across the membrane, the methanol or the molecules inside the cell? What causes these molecules to move? How do they cross the membrane? What affects their rate of movement? Why doesn’t lysis occur in all of the solutions?

Answer 1

Answer.

a). When the RBC's are placed in 300mM methanol solution, the methanol molecules will move inside the RBC's cytoplasm as the RBC's cytoplasm lacks methanol molecules.

b). The solute in RBC's cytoplasm are salts and dissolved gases which contribute towards the osmolarity of cytoplasm.

c). The methanol molecules / ions formed in the methanol solution will contribute towards the osmolarity of the surrounding solution.

d). Yes, the osmotic gradient will change until the cytoplasm and the surrounding reach equilibrium.

e). The methanol molecules are moving inside the cell as there is a conc. gradient and membrane is permeable to methaol molecules and not to the salts inside the cell.

f). The membrane is made up of phospholipids and alcohol molecules are permeable to phospholipid layer. so they easily cross the membrane. The osmotic gradient affects the rate of movement.

g). The lysis doenn't occur because the osmolarity reaches equlibrium in both surrounding and the cytoplasm. Lysis would have occurred if the osmotic gradient was high.