Select the diagram (1, 2, or 3) that represents the shape of a red blood cell when placed in each of the following a to e: (9.6)
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a. 0.9% (m/v) NaCl solution

Verified step by step guidance

1. Understand the concept of osmosis and tonicity: Osmosis is the movement of water across a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration. Tonicity refers to the relative concentration of solutes in a solution compared to the inside of a cell, which affects the cell's shape.
2. Identify the type of solution: A 0.9% (m/v) NaCl solution is considered isotonic to human red blood cells. This means the solute concentration inside the red blood cell is equal to the solute concentration in the surrounding solution.
3. Predict the effect of an isotonic solution on a red blood cell: In an isotonic solution, there is no net movement of water into or out of the cell. The red blood cell maintains its normal shape, which is a biconcave disk.
4. Relate the information to the diagrams: Examine the provided diagrams (1, 2, or 3) and identify which one represents the normal biconcave shape of a red blood cell. This shape corresponds to the cell in an isotonic solution.
5. Select the correct diagram: Based on the understanding of isotonic solutions and the normal shape of red blood cells, choose the diagram that matches the description of a red blood cell in a 0.9% (m/v) NaCl solution.

Key Concepts

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. In the context of red blood cells, understanding osmosis is crucial for predicting how cells will behave in different solutions, such as isotonic, hypotonic, or hypertonic environments.

Isotonic Solutions

An isotonic solution has the same solute concentration as the inside of a cell, resulting in no net movement of water. For red blood cells, a 0.9% (m/v) NaCl solution is isotonic, meaning the cells will maintain their normal biconcave shape without swelling or shrinking.

Cellular Response to Solutions

Cells respond differently to various solute concentrations. In hypotonic solutions, cells may swell and potentially burst, while in hypertonic solutions, they may shrink. Understanding these responses is essential for predicting the shape of red blood cells in different saline environments.