Osmosis - SS1 Biology Lesson Note
In biology, osmosis refers to the movement of solvent molecules (usually water) across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration. It is a specific type of passive transport that plays a crucial role in maintaining the balance of water and solutes within cells and across biological systems.
Key characteristics of osmosis include:
1. Selectively Permeable Membrane: Osmosis occurs across a selectively permeable membrane that allows the passage of solvent molecules (such as water) while restricting the movement of solute molecules.
2. Concentration Gradient: Osmosis is driven by a
concentration gradient of solute particles. Water molecules move from regions of lower solute concentration (hypotonic) to regions of higher solute concentration (hypertonic) to equalize the solute concentrations on both sides of the membrane.
3. Water Movement: Osmosis specifically refers to the movement of water molecules. It is important to note that osmosis does not involve the movement of solute particles themselves.
4. Equilibrium: Osmosis continues until an equilibrium is reached, where there is an equal concentration of water molecules on both sides of the membrane. At equilibrium, there is no net movement of water, although individual water molecules continue to move back and forth.
5. Osmotic Pressure: The movement of water through osmosis generates osmotic pressure. This pressure can cause changes in cell volume and exert influence on biological structures and processes.
Osmosis is critical for various biological functions, including the regulation of water balance and cell shape. It is particularly important in processes such as osmoregulation in organisms, the absorption of water by plant roots, the movement of water in plant vascular tissues, and the maintenance of proper cell turgor pressure.
In biological systems, solutions can be categorized as isotonic, hypotonic, or hypertonic:
§ Isotonic Solution: An isotonic solution has the same concentration of solutes as the cell. In this case, there is no net movement of water, and the cell maintains its shape and volume.
§ Hypotonic Solution: A hypotonic solution has a lower concentration of solutes compared to the cell. Water moves into the cell through osmosis, causing the cell to swell and potentially burst (lyse).
§ Hypertonic Solution: A hypertonic solution has a higher concentration of solutes compared to the cell. Water moves out of the cell through osmosis, causing the cell to shrink (plasmolysis).
Understanding osmosis is essential for comprehending processes such as hydration, waste elimination, and the regulation of water balance in living organisms.
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