Problem 14 - Biology: The Unity and Diversity of Life

Question

Immerse a human red blood cell in a hypotonic solution, and water ____. a. diffuses into the cell b. diffuses out of the cell c. shows no net movement d. moves in by endocytosis

Step-by-Step Solution

Answer

In a hypotonic solution, water diffuses into the cell.

Step 1: Understanding the Concepts

To solve this exercise, we need to understand how water movement occurs in cells when placed in different types of solutions: isotonic, hypertonic, and hypotonic. A hypotonic solution has a lower solute concentration compared to the inside of the cell, leading to water movement dynamics based on osmosis.

Step 2: Analyzing Osmosis

In a hypotonic solution, water will always move from the area of lower solute concentration (the solution) to the area of higher solute concentration (inside the cell) due to osmosis. This is to equalize the solute concentrations on both sides of the cell membrane.

Step 3: Conclusion

With a hypotonic solution, the external environment is more diluted than the cell's interior. Therefore, water will move into the cell, causing it to swell and possibly burst. The correct answer is option a: water diffuses into the cell.

Key Concepts

Hypotonic Solution

A hypotonic solution occurs when the concentration of solutes outside the cell is lower than the concentration inside the cell. This creates an imbalance that leads to the movement of water across the cell membrane. Key features of a hypotonic solution include:

• Lower concentration of solutes compared to the cell's interior
• More water outside the cell than inside

When a cell, such as a red blood cell, is placed in a hypotonic solution, it will begin to absorb water. The process happens through osmosis, which is the movement of water across a semi-permeable membrane—from an area of lower solute concentration to an area of higher solute concentration. In simple terms, the hypotonic solution attempts to even out the concentration differences by sending water into the cell, which can lead to the cell swelling.

Water Movement

Water movement is a natural phenomenon driven by the process of osmosis. It is crucial for the maintenance of cell structure and function. In the context of osmosis, water will always move from an area where it is more concentrated to an area where it is less concentrated. This movement is regulated by:

• Concentration differences on either side of a semi-permeable membrane
• The selective permeability of the cell membrane, allowing water through

In a hypotonic environment, water would move into the cell due to the lower concentration of solutes outside. This influx of water increases the cell's internal pressure, known as turgor pressure, which can result in the cell expanding and potentially bursting if too much water enters.

Red Blood Cell

Red blood cells, or erythrocytes, are specialized cells in the human body primarily responsible for oxygen transport. These cells are particularly sensitive to changes in surrounding solution concentrations because they lack a rigid cell wall. When red blood cells are immersed in a hypotonic solution:

• Water enters the cell by osmosis
• The cell swells due to increased water intake

Unlike plant cells that have a cell wall to provide structural support and prevent bursting, red blood cells can rupture—a process known as hemolysis—if the swelling is excessive. Understanding this behavior is vital in fields like medicine and biology, where cell integrity and the effects of osmotic imbalances are commonly observed.