Passive Transport • transport of molecules across the cell membrane that does not require energy! • 3 Types: 1) Diffusion 2) Osmosis 3) Facilitated Diffusion 1. Diffusion • 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 http://student.ccbcmd.e du/courses/bio141/lecg uide/unit3/eustruct/pas sive_flash.html 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. http://www.stolaf.edu/peopl e/giannini/flashanimat/trans port/osmosis.swf • 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. • Picture: http://www.nclark.net/osmosisPocus.gif Real Life Ex: • 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. Real Life Ex: • 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.