Diffusion • Particles naturally travel from areas where they are crowded to areas where they are less crowded. http://www.indiana.edu/~phys215/lecture/lecnotes/lecgraphics/diffusion.gif • Diffusion is the movement of particles from an area where their concentration is high to an area where their concentration is low.
Osmosis • All living organisms depend on water • Living cells are surrounded by and filled with fluid that is made up mostly of water • The diffusion of water across a cell membrane is so important to life processes that it has been given a special name – osmosis. http://www.himalayancrystalsalt.com/wellness/osmosis.gif
*Checkpoint* • What would happen to a grape if you placed in a dish full of pure water? • What would happen to a grape if you placed it in water mixed with a large amount of sugar? >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> http://www.ndpteachers.org/perit/osmosis2.gif
Moving Small Particles • Some particles (such as water and oxygen) are small enough to diffuse directly through the cell membrane • Others (such as sugar and amino acids) are too large to squeeze through the membrane and require protein “doorways” in order to enter or leave the cell. http://fig.cox.miami.edu/~cmallery/150/memb/c8x16types-transport.jpg
Passive Transport • Passive transport is the diffusion of particles through proteins. • These particles move from an area of high concentration to an area of low concentration. • Requires NO ENERGY http://discover.edventures.com/images/termlib/p/passive_transport/support.gif
Active Transport • Active transport is the movement of particles through proteins against the normal direction of diffusion. • Particles are moved from an area of low concentration to an area of high concentration • Requires ATP
Moving Large Particles • Endocytosis • Means “within the cell” • Cell membrane surrounds a particle and once the particle is completely surrounded, the vesicle pinches off and enters the cell. http://jan.ucc.nau.edu/~lrm22/lessons/endocytosis/endocytosis.gif
Moving Large Particles • Exocytosis • Vesicles inside the cell travel to the cell membrane and fuse with it to release the particles. http://upload.wikimedia.org/wikipedia/commons/thumb/1/16/Exocytosis_types.svg/399px-Exocytosis_types.svg.png