Overview
This lecture explains osmosis, clarifies water concentration, and shows how these concepts apply to movement of water in and out of cells.
Diffusion Recap
- Diffusion is the net movement of particles from higher to lower concentration.
- Oxygen and glucose molecules enter cells by diffusing down their concentration gradient.
Osmosis: Definition and Explanation
- Osmosis is a special case of diffusion: the movement of water molecules.
- Osmosis occurs across a partially permeable membrane.
- Water moves from a region of higher water concentration to a region of lower water concentration.
Water Concentration and Solutes
- Water concentration refers to the amount of water compared to dissolved molecules (solutes) like sugars or salts.
- Adding more solute lowers a solution's water concentration.
- It’s the proportion of water to solute, not just water volume, that matters for concentration.
Application of Osmosis to Cells
- Cells have a partially permeable membrane separating inside from outside.
- If the outside of a cell has higher water concentration (fewer solutes) than the inside, water enters the cell by osmosis.
- Water moves from outside (high water concentration) to inside (low water concentration) down its concentration gradient.
Key Terms & Definitions
- Diffusion — Net movement of particles from higher to lower concentration.
- Osmosis — Net movement of water molecules across a partially permeable membrane from high to low water concentration.
- Solute — A substance dissolved in a liquid (like sugar or salt in water).
- Partially permeable membrane — A barrier that allows some substances (like water) to pass but not others.
- Water concentration — Proportion of water compared to dissolved solutes in a solution.
Action Items / Next Steps
- Optional: Review the previous video on diffusion for better understanding.
- Practice questions on osmosis and diffusion, if available.
- Watch related videos or follow the provided lesson link for further study.