Are the following solutions isotonic, hypotonic, or hypertonic compared with a red blood cell?
c. 0.9% (m/v) NaCl

Verified step by step guidance

1. Understand the concept of tonicity: Tonicity refers to the relative concentration of solutes in a solution compared to another solution. In this case, we are comparing the NaCl solution to the fluid inside a red blood cell. A solution can be isotonic (same concentration), hypotonic (lower concentration), or hypertonic (higher concentration).
2. Recall the isotonic concentration for red blood cells: The isotonic concentration of NaCl for red blood cells is 0.9% (m/v). This means that a solution with 0.9% (m/v) NaCl will not cause water to move into or out of the red blood cells.
3. Compare the given solution's concentration to the isotonic concentration: The problem states that the solution is 0.9% (m/v) NaCl. Compare this value to the isotonic concentration of 0.9% (m/v).
4. Determine the tonicity: If the given solution's concentration is equal to 0.9% (m/v), it is isotonic. If it is less than 0.9% (m/v), it is hypotonic, and if it is greater than 0.9% (m/v), it is hypertonic.
5. Conclude based on the comparison: Since the given solution is 0.9% (m/v) NaCl, it matches the isotonic concentration for red blood cells. Therefore, the solution is isotonic.

Key Concepts

Tonicity

Tonicity refers to the ability of a solution to affect the volume and pressure of a cell by osmosis. It is classified into three categories: isotonic, hypotonic, and hypertonic, based on the relative concentration of solutes in the solution compared to the cell's interior. Understanding tonicity is crucial for predicting how cells will respond to different solutions.

Isotonic Solutions

An isotonic solution has the same solute concentration as the inside of a cell, resulting in no net movement of water across the cell membrane. For red blood cells, an isotonic solution maintains their shape and function, preventing swelling or shrinking. A common example is a 0.9% (m/v) NaCl solution, which is often used in medical settings.

Osmosis

Osmosis is the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. This process is vital for maintaining cellular homeostasis. In the context of red blood cells, understanding osmosis helps explain how different solutions can lead to cell lysis in hypotonic solutions or crenation in hypertonic solutions.