#Osmosis #biology #textbook #igcse

Pg:- 46,47,48

Ch:- 3

Osmosis is a natural process where water moves across a selectively permeable membrane. This process is crucial for maintaining the balance of fluids in cells and is essential for life.

• The Basics: Osmosis refers to the movement of water from an area of low solute concentration (where there’s a lot of water compared to solutes like salt or sugar) to an area of high solute concentration (where there’s less water compared to solutes). This movement continues until there’s an equal concentration of water and solutes on both sides of the membrane.

• Selective Permeability: The membrane acts like a bouncer at a club, letting water in and out while keeping other substances (like salts or sugars) in check. This property is what makes osmosis so vital for cell function.

• Phospholipid Bilayer: The fundamental structure of cell membranes is made up of phospholipids. This bilayer structure creates a barrier that selectively allows certain molecules to pass through.

• Concentration Gradient: Osmosis is influenced by the concentration gradient, which is the difference in solute concentrations across the membrane. Water moves from areas with less solute (more water) to areas with more solute (less water).

• Dynamic Equilibrium: The goal of osmosis is to reach a state of equilibrium, where the concentrations of solute and water are balanced on both sides of the membrane. This ensures that cells stay healthy and maintain their shape.

• Real-Life Examples:

  • Raisins in Water: When you place a raisin in water, it swells up because water moves into the raisin, where there’s a higher concentration of solutes (sugars) compared to the water outside. This demonstrates osmosis in action.

  • Plant Cells: Plants use osmosis to absorb water from the soil. When the soil is moist, water moves into the roots, helping the plant stay turgid and upright.

• Importance in Biology: Osmosis plays a critical role in various biological processes, including:

  • Nutrient Absorption: Cells take in water and nutrients essential for survival.

  • Waste Removal: Water helps flush out waste products from cells.

  • Homeostasis: Osmosis helps maintain the internal environment of cells, allowing them to function properly.

• Osmotic Pressure: This is the pressure needed to stop the flow of water through the membrane. It’s a crucial factor in how cells regulate their internal environment.