2.4.8 Comparing Osmosis in Animal & Plant Cells

Key Differences Between Osmosis in Animal and Plant Cells:

Feature	Animal Cells	Plant Cells
Cell Wall	Absent – cannot resist changes in shape or volume.	Present – provides structural support and resists bursting.
Response in Hypotonic Solution	Water enters the cell; it swells and may burst (lysis).	Water enters the cell; it becomes turgid (swollen) but does not burst due to the cell wall.
Response in Isotonic Solution	No net movement of water; the cell maintains its normal shape.	No net movement of water; the cell remains in its normal state.
Response in Hypertonic Solution	Water leaves the cell; it shrinks and becomes crenated (wrinkled).	Water leaves the cell; the vacuole shrinks, and the membrane pulls away from the wall (plasmolysis).

Hypotonic Solution (Higher Water Potential Outside the Cell):

• Animal Cells:
  • Water enters by osmosis, causing the cell to swell.
  • If too much water enters, the cell bursts due to lack of a cell wall (lysis).
  • Example: Red blood cells in distilled water undergo haemolysis.
• Plant Cells:
  • Water enters by osmosis, and the cell becomes turgid.
  • The vacuole swells, and the cytoplasm presses against the cell wall.
  • The cell wall prevents bursting, maintaining structural integrity.

Isotonic Solution (Equal Water Potential Inside and Outside the Cell):

• Animal Cells:
  • No net movement of water.
  • Cells retain their normal shape and function.
• Plant Cells:
  • No net movement of water.
  • Cells remain in their normal state, not turgid or plasmolysed.

Hypertonic Solution (Lower Water Potential Outside the Cell):

• Animal Cells:
  • Water leaves the cell by osmosis, causing the cell to shrink and become crenated.
  • The cell loses function if dehydrated.
• Plant Cells:
  • Water leaves the cell, and the vacuole shrinks.
  • The cytoplasm pulls away from the cell wall (plasmolysis), which may damage the cell.
  • Plasmolysed cells lose turgor pressure, causing wilting in plants.

Importance of Osmosis in Both Cell Types:

1. Animal Cells:

• Osmosis maintains the balance of fluids and electrolytes, essential for processes like nerve impulses and muscle contractions.
• Prevents dehydration or overhydration.

2. Plant Cells:

• Maintains turgidity, which provides structural support for leaves and stems.
• Regulates water uptake for photosynthesis and nutrient transport.