Bell Work! 1. Why are vacuoles important to PLANTS? Passive and Active Transport Passive Transport Cells always move particles in or out of a cell. Cells can use passive transport to move molecules across a cell membrane WITHOUT using energy. Osmosis and diffusion are two types of passive transport. Diffusion Diffusion is the movement of molecules in a fluid or gas from an area of high concentration (lots of molecules) to an area of lower concentration (less molecules). Ex: Small lipids, oxygen, and carbon dioxide diffuse across a membrane. Osmosis Occurs when water moves from a higher concentration to an area with a lower concentration of water. Osmosis Animation Isotonic, Hypertonic and Hypotonic Isotonic: A solution (external to the cell) is isotonic to a cell if it has the same concentration of particles as the cell. Hypertonic: A hypertonic solution has a higher concentration of particles compared to the inside of a cell. Hypotonic: A hypotonic solution has a lower concentration of dissolved particles compared to the inside of a cell. Facilitated Diffusion Some molecules cant diffuse easily across a cell membrane. Facilitated diffusion is the diffusion of molecules across a membrane (down the concentration gradient) using transport proteins (proteins make it easier to move stuff). What is Active Transport? It drives molecules across a membrane from a region of low concentration to a region of high concentration. Active transport USES ENERGY called ATP Active Transport Continued It uses transport proteins to move substances against the concentration gradient Transportation of Materials in a Cell Endocytosis: process of taking large molecules into a cell by engulfing them in a membrane. Exocytosis: release of substances out of a cell by using vesicles that attach to the membrane to release contents. Phagocytosis Phagocytosis: means cell eating. Help to fight infection by eating bacteria and destroying them.