Homeostasis – Maintaining a Balance • Cells must keep the proper concentration of nutrients and water and eliminate wastes. • The cell membrane is selectively permeable – it will allow some things to pass through, while blocking other things.
Types of Cellular Transport • 1. Passive transport – no energy is needed to move particles. • Diffusion – movement of particles from an area of high concentration to an area of low concentration. • Facilitated diffusion – embedded proteins act as tunnels allowing particles to “fall” through. • Channel Proteins • Carrier Proteins
Osmosis – a special type of diffusion • Diffusion of water across a selectively permeable membrane. • Occurs until water is balanced on both sides of the membrane.
2. Active transport – energy is needed (by the mitochondria) to move particles. The particles move from a low concentration to a high concentration. • Endocytosis– taking something into the cell. • Exocytosis – expelling something from the cell.
Cell Concentrations - Tonicity • Hypertonic solutions – more dissolved solute. • Hypotonic solutions – less dissolved solute. • Isotonic solutions – the same dissolved solute. http://www.zerobio.com/flashmx/tonicity.swf