Passive Transport transport of molecules across the cell membrane that does not require energy! 3 Types: 3 Types: 1) Diffusion 2) Osmosis 3) Facilitated Diffusion

more less Diffusion = the movement of particles from an area where they are more concentrated to an area where they are less concentrated Type of passive transport; does NOT require energy! HIGH TO LOW uide/unit3/eustruct/passive_flash.html 1. Diffusion

2. Osmosis The cell membrane is permeable to water; water can move freely through it. Osmosis is the diffusion of water across the cell membrane. e/giannini/flashanimat/trans port/osmosis.swf

Examples: If you place a cell into a solution where the concentration of solute (salt or sugar) is HIGHER in the solution than in the cell, then water will move _________________ the cell. Picture: If you place a cell into a solution where the concentration of solute (salt or sugar) is LOWER in the solution than in the cell, then water will move _________________ the cell.

A cell has lots of sugars and salts inside it. If you place it in pure water, which way would the water flow? _____________________________ In animal cells, it would continue until the cell burst! In plant cells, the cell wall would keep it from bursting.

Turgor pressure: is the pressure on the cell walls from the amount of water moving into or out of the cell.

A cell has lots of sugars and salts inside it. However, if you placed it in pure sugar or salt, which way would water flow? ________________________________ The animal cell shrivels, and the plant cell’s cytoplasm is pulled away from the cell wall. This is called plasmolysis.

3. Facilitated Diffusion Facilitated means to “help” Some molecules (like glucose) are way too big to diffuse through the plasma membrane. These molecules move through membrane proteins that have a hole in the middle. These proteins are called channel proteins. This is still diffusion! Molecules can only move across the membrane to an area of lower concentration.