Animal cells are enclosed in a cell membrane made of a phospholipid bilayer.The cytoplasm has various solutes dissolved in it so has a negative water potential.The diameter of a red blood cell is about 7μm. If a red blood cell is placed in pure water, water will move into the cell by osmosis.The cell membrane cannot stretch much so it will break (lysis) and the contents of the cell will be released.In red blood cells this is called haemolysis.If a red blood cell is placed in a solution with a lower water potential, water will leave the cytoplasm and the cell will shrink (crenation).It is necessary for animal cells to be in a medium with the same water potential to prevent damage by osmosis.
Osmosis in Animal Cells
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Specification: AQA Biology (7401), AS-level, 3.2.3 Transport across cell membranes. Topic: Transport Across Cell Membranes.
Key terms in this lesson
- phospholipid
- A lipid in which one fatty acid is replaced by a phosphate group, giving a hydrophilic head and hydrophobic tails.
- osmosis
- The net movement of water molecules from a region of higher water potential to a region of lower water potential through a selectively permeable membrane.
- water potential
- The pressure created by water molecules, a measure of the tendency of water to move out of a solution; pure water has a water potential of zero and solutes make it more negative.
More in Transport Across Cell Membranes
- Protein Channels
- Carrier Proteins
- Water Potential Ψ
- Osmosis
- Osmosis in Plant Cells
- Active Transport
- Sodium-Potassium Pump
- Increasing the Rate of Movement across a Membrane
All 22 lessons in Transport Across Cell Membranes · All AQA AS-level Biology topics