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This video shows the effect of different types of solution on red blood cells. Instead of using red blood cells, visking tubing models are used. Click here to watch the video.
Key Terms
Isotonic = Solution has the same water potential as the cells. Eg Cell buffer
Hypertonic = Solution has a lower water potential (ie a larger amount of solutes) than the cells. Eg Concentrated salt solution.
Hypotonic = Solution has a higher water potential (ie a lower amount of solutes) than the cells. Eg Dilute salt solution.
Osmosis in Animal Cells
(1) Animal cells placed in isotonic solution
No net gain or loss of water from the animal cells.
Animal cells do not change in size.
(2) Animal cells placed in hypertonic solution
Net loss of water from the animal cells. (Process is known as exosmosis.)
Animal cells shrink.
(3) Animal cells placed in hypotonic solution
Net gain of water from the animal cells. (Process is known as endosmosis.)
Animal cells expand and burst causing the cell contents to be released. (Process = lysis).
Figure 8 Effects of osmosis on red blood cells.
Osmosis in Plant Cells
Fig 9 Effect of osmosis on plant cells.
When placed in a solution with a higher water potential
Water flows through the plasma membrane and tonoplast into the central vacuole by osmosis. (Process = endosmosis) --> The cell expands.
Cell contents exert pressure on the cell wall and the pressure is known as turgor pressure.
Plant cell does not burst as the cell wall is stretched and pushes back against the cell contents. This pressure opposes the turgor pressure and prevents plant cells from bursting.
The cell is described as TURGID.
When placed in a solution with a lower water potential
Water moves out of cell vacuoles and tonoplasts of plant cells by osmosis (Process = exosmosis).
Volume of plant cells shrink.
Cell membrane pulls away from the cell wall leaving gaps between the cell wall and cell membrane. Process is known as PLASMOLYSIS.
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