Question

You are given a solution into which you drop some red blood cells. The solution contains 350mOsMNaCl in water. The cells contain an ICF concentration of nonpenetrating solutes (NPS) equal to 350mOsM. Which of the following statements is correct regarding osmotic concentration and tonicity in this situation? (Note: NaCl is a NPS and dissociates into Na+&Cl−; however, I have already put all units of concentration into mOsM for you).

a)the cell is hyposmotic and hypotonic to the solution
b)the cell is hyperosmotic and hypertonic to the solution
c)the cell is isosmotic and isotonic to the solution
d)the tonicity cannot be determined

Answer 1

The cells are isosmotic and isotonic to the solution as both have the same osmolarity, resulting in no net water movement and the maintenance of normal cell volume and shape.

Step-by-step explanation:

The correct statement regarding the osmotic concentration and tonicity when red blood cells with an intracellular fluid (ICF) concentration of nonpenetrating solutes (NPS) equal to 350 mOsM are placed into a solution containing 350 mOsM NaCl is (c) the cell is isosmotic and isotonic to the solution. Since NaCl dissociates into Na+ and Cl−, each NaCl unit contributes to two particles, which has already been accounted for in the mOsM measure provided. An isotonic solution means that the extracellular fluid has the same osmolarity as the cells, resulting in no net movement of water into or out of the cells. This allows the cells to maintain their normal volume and shape.

In contrast, cells in a hypotonic solution would swell, as water would enter the cell to equilibrate the osmolar imbalance, and in a hypertonic solution, cells would shrink because water would exit the cell.