Question

All of the following statements are false about red blood cells that have been added to a flask of saturated NaCl solution, except that
A. The cells will undergo mitosis
B. The cells will increase in volume
C. The cell will lose water
D. The cells are hypertonic relative to the surrounding medium
E. The concentration of NaCl is tower outside the cells than inside

Answer 1

Hint: Here the answer can be given by the concept of osmosis. Osmosis is a very important procedure as it works in biological systems because biological membranes are semipermeable. These membranes are impermeable to large and polar molecules such as ions, proteins, and polysaccharides.

Complete answer:
Let’s see the definition and working principle of osmosis.
Osmosis: Osmosis is a procedure in which solvent molecules move through a selectable permeable membrane into a higher concentration of solute. This procedure works in a way that equalizes the solute concentration on the two sides.
Here most of the time solvent is water and solute can be any other solution. Osmosis works only in a situation where two solutions have been separated by a selectable permeable membrane.
Coming back to our question, when the red blood cells are added into the flask of saturated/ concentrated NaCl, the process of osmosis takes place. The plasma membrane of red blood cells works as a selectable membrane and water molecules can be easily transferred. In NaCl concentrated solution, there are less amounts of water molecules present while in the red blood cell, the number of water molecules is much higher. So when the red blood cells come in contact with saturated NaCl, the water molecule from red blood cells moves to NaCl solution as they are in higher concentration in red blood cells.
So, the correct answer is C, the cell will lose water.

Note:
Due to osmosis, three kinds of red blood cells can be seen such as hypertonic, isotonic, and hypotonic. Here in our question, the red blood cells lose water and gain a hypertonic situation. When placed in water, red blood cells gain water molecules and become hypotonic.