The bursting of a red blood cell placed  in a hypotonic solution is called

Step 1: Analyze the question A red blood cell is placed in a hypotonic solution, meaning the solution has a lower solute concentration (more water) than the cell's cytoplasm. We need the term for the cell bursting.

Step 2: The concept Water moves by osmosis from a region of high water potential to one of low water potential, across a partially permeable membrane.

• In a hypotonic solution, water enters the red blood cell.
• The cell swells. Animal cells have no cell wall, so the membrane eventually ruptures and the cell bursts.

Step 3: Examine each option

• A. Crenation: the shrinking and shriveling of a red blood cell in a hypertonic solution. This is the opposite process.
• B. Haemolysis: the bursting of red blood cells, releasing haemoglobin. It fits the question exactly.
• C. Plasmolysis: the shrinking of the protoplast away from the cell wall in a plant cell placed in a hypertonic solution.
• D. Cytolysis: the bursting of any cell by osmotic swelling. It is a general term, and it is technically also true for a red blood cell. But when the cell is specifically a red blood cell, the standard term is haemolysis.

Step 4: Answer The question specifically names a red blood cell, so the precise term is haemolysis (haemo = blood, lysis = breaking).

Note: Cytolysis (D) is a broader term that could also describe this event, so the question is a little loose. The examiners clearly want the term specific to red blood cells, which is haemolysis.

Exam tip:

• Hypotonic + red blood cell → swell and burst → haemolysis
• Hypertonic + red blood cell → shrink → crenation
• Hypertonic + plant cell → plasmolysis
• Hypotonic + plant cell → becomes turgid (the cell wall prevents bursting)

Remember: "Haemo" = blood. If the question says red blood cells, think haemolysis.