* Simple Diffusion: The movement of a substance from an area of high concentration to an area of low concentration, following the concentration gradient. This requires no energy input. Think of how a drop of food coloring spreads out in a glass of water.
* Facilitated Diffusion: Similar to simple diffusion, but it uses transport proteins embedded in the cell membrane to help substances cross the membrane. This is still passive, as it doesn't require the cell to expend energy, but the transport protein acts as a facilitator.
* Osmosis: The movement of water across a semipermeable membrane from an area of high water concentration (low solute concentration) to an area of low water concentration (high solute concentration). This is driven by the difference in water potential and doesn't require the cell to use energy.
Important Note: While these processes are considered passive, they still rely on the cell maintaining its membrane structure and the proper function of the transport proteins involved in facilitated diffusion.
Let me know if you want a more detailed explanation of any of these processes!
