Question

When blood cells are placed in 1% (w/v) NaCl aqueous solution:

• A. Cell will burst
• B. Cell will shrink
• C. Cell will swell
• D. Cell remains as such

Hint:

Key Exam Tip:
When dealing with osmosis and cell behavior:
• Hypertonic Solution: Higher solute concentration outside the cell $\implies$ water moves out $\implies$ cell shrinks (crenation).
• Hypotonic Solution: Lower solute concentration outside the cell $\implies$ water moves in $\implies$ cell swells and may burst (hemolysis).
• Isotonic Solution: Equal solute concentration $\implies$ no net water movement $\implies$ cell maintains shape. For red blood cells, 0.9% NaCl is approximately isotonic.

Answer 1

The Correct Option is B

The behavior of blood cells when placed in a solution of varying concentration is governed by the principle of osmosis. Osmosis is the net movement of solvent molecules (in this case, water) through a selectively permeable membrane from a region of higher solvent concentration (lower solute concentration) to a region of lower solvent concentration (higher solute concentration). Blood cells have a semipermeable membrane. The concentration of the solution is given as 1% (w/v) NaCl. This concentration is generally considered hypertonic relative to the cytoplasm of mammalian red blood cells, which has an approximate osmotic concentration equivalent to 0.9% NaCl.
• Hypertonic Solution (1% NaCl): When blood cells are placed in a hypertonic solution, the concentration of solutes (NaCl) outside the cells is higher than inside the cells. Consequently, the concentration of water is lower outside the cells than inside. Water will move by osmosis from the region of higher water concentration (inside the cell) to the region of lower water concentration (outside the cell) across the cell membrane. This loss of water causes the cell to shrink, a process known as crenation.
• Hypotonic Solution: If the blood cells were placed in a hypotonic solution (e.g., pure water or a very dilute salt solution, < 0.9% NaCl), water would move into the cells, causing them to swell. In extreme cases, they could burst (hemolysis).
• Isotonic Solution (approx. 0.9% NaCl): In an isotonic solution, the solute concentration outside the cells is equal to that inside the cells. There is no net movement of water, and the cells maintain their normal shape and volume. Since the given solution is 1% NaCl, which is hypertonic, water will leave the blood cells, causing them to shrink. Final Answer: \(\boxed{b}\)