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: OCR Biology A (H020), AS-level, 2.1.5 Biological membranes. Topic: Plasma Membrane.
Key terms in this lesson
- phospholipid bilayer
- Two layers of phospholipid molecules arranged with hydrophilic heads facing outwards and hydrophobic tails facing inwards, forming the basic structure of cell membranes.
- 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
- A measure of the tendency of water molecules to move out of a solution; pure water has a water potential of zero and adding solute lowers it.
More in Plasma Membrane
- Solvents
- Diffusion
- Diffusion Across Membranes
- Facilitated Diffusion
- Active Transport
- Bulk Transport
- Osmosis
- Osmosis in Plant Cells
All 18 lessons in Plasma Membrane · All OCR AS-level Biology topics