Question

Why do red blood cells swell up and burst when placed in pure water?

Short answer

Red blood cells swell and burst in pure water due to osmosis, as water enters the cells, leading to increased pressure.

Step-by-step solution

Understanding Osmosis

Osmosis is the movement of water across a semipermeable membrane, from an area of low solute concentration to an area of high solute concentration. The red blood cell membrane allows water to pass through but not larger solutes.

Comparing Solute Concentrations

Red blood cells have a higher concentration of solutes (like salts, proteins, and ions) inside them compared to pure water, which has no solutes.

Water Movement Direction

When red blood cells are placed in pure water, water moves into the cells via osmosis because water flows towards the higher concentration of solutes inside the cells.

Effect of Water Influx

As water continues to enter the cells, the pressure builds up inside, causing the red blood cells to swell.

Bursting of Red Blood Cells

If the influx of water is substantial, the cell membrane cannot hold the increasing volume, leading to the bursting of the red blood cells, a process known as hemolysis.

Key concepts

Red Blood Cells

Red blood cells, or erythrocytes, are a crucial component of our blood. They carry oxygen from our lungs to the rest of our body and return carbon dioxide to the lungs for exhalation. This process is vital for maintaining our body's overall function. Red blood cells are characterized by their distinctive biconcave shape, which increases their surface area.

This shape is significant because it aids in the efficient exchange of gases. The cell membrane surrounding red blood cells is flexible, allowing them to travel through narrow blood vessels. However, this membrane is also semipermeable, meaning it selectively allows certain substances, like water and gases, to pass while blocking others.

Semipermeable Membrane

A semipermeable membrane is essential for maintaining cellular integrity and is found in all cells, including red blood cells. These membranes selectively allow certain molecules or ions to pass through while blocking others, playing a key role in cellular processes, including osmosis.

In the case of red blood cells, the semipermeable membrane permits water and small solutes to pass but prevents larger molecules, such as proteins, from crossing. This selective permeability is crucial for maintaining the cell’s internal environment and ensuring it functions correctly.

• Allows water and small molecules to move between the cell and surrounding environment.
• Restricts access of larger, potentially harmful molecules.

Understanding the role of these membranes helps us grasp how cells interact with their environment and how various processes are controlled within the body.

Hemolysis

Hemolysis is the process where red blood cells burst open, releasing their contents into the surrounding fluid. This phenomenon occurs under certain conditions, such as when red blood cells are placed in a hypotonic solution like pure water.

Due to osmosis, water enters the cell where the solute concentration is higher. As water continues to flow in, the cell swells and pressure builds up against the cell membrane. If the membrane cannot withstand this pressure, it ruptures, leading to hemolysis.

• Occurs when red blood cells are placed in a solution with too low solute concentration.
• Continued water influx causes the cell to swell beyond its capacity.
• Results in the release of the cell's internal components.

Understanding hemolysis helps us prevent and manage its impact in medical settings, ensuring patient safety.