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Transcript
Transporting Materials Across the Cell Membrane Osmosis, Diffusion, and Active Transport Demonstration • Sketch a diagram of the beaker and water • Get a colored pencil and draw what happens the instant the dye hits the water Diffusion • Is the movement of materials from a region of high concentration to a region of low concentration • Equilibrium is reached when the concentrations are equal • You experience this when burnt toast from the kitchen wafts down to your room Demonstration, cont’d • Observe the beaker with dye now • How is it different from when the dye first went in? Osmosis • Is the movement of water from a region of high concentration to a region of low concentration until equilibrium is reached • You experience osmosis when lettuce left out on the counter wilts – the water is moving from high conc (in lettuce) to low conc (in air) • Both diffusion and osmosis are passive – do not require ATP (energy) Cell Membrane • Is composed of a double layer of lipid molecules in which proteins are embedded • Cell membrane regulates passage of substances into and out of the cell and is said to be a selectively permeable membrane, meaning not all substances will pass through it Cell Membrane Cell Membrane • Many substances can pass freely through the cell membrane, such as water, CO2 and O2 • Other substances are too large to fit through the pores and need help. Carrier proteins aid in moving large molecules from the outside to the inside of the cell. This is called… Facilitated Diffusion Demonstration Note that molecules are moving from a region of high conc to a region of low conc. Therefore, this is still diffusion. http://bio.winona.msus.edu/berg/ANIMTNS/FacDiff.htm How Facilitated Diffusion Works • http://highered.mcgrawhill.com/sites/0072495855/student_ view0/chapter2/animation__how_fac ilitated_diffusion_works.html Active Transport • Sometimes substances that need to get into cells are in higher conc in the cells – diffusion won’t work • Some materials are transported against a conc gradient (from low to high). In these cases energy must be used. Energy in cells is ATP. Active Transport • Active transport is the movement of a substance from a region of low conc to a region of high conc with the expenditure of energy • Without active transport, your kidneys would not reabsorb precious water, your muscles would not contract, and your nerves could not carry impulses. Active Transport Carrier proteins require energy in the form of ATP to move the substances across the membrane Endocytosis • Very large molecules must sometimes get into the cell but will not fit through the pores nor the carrier proteins • Endocytosis is a process where a cell engulfs large particles by extending its cytoplasm around the particle, trapping the particle in a vacuole. Endocytosis Two types: 1) Phagocytosis is when the cell engulfs solid particles 2) Pinocytosis is when the cell engulfs liquid droplets. Exocytosis • Exocytosis is the process by which large molecules are transported out of the cell, such as waste materials. • The Golgi complex packages the departing substances into vesicles, which fuse with the cell membrane and rupture, dumping their contents to the outside. Exocytosis Endocytosis/Exocytosis Animation • http://highered.mcgrawhill.com/olc/dl/120068/bio02.swf Summary Passive Active (no ATP required) (ATP required) Diffusion Active Transport Osmosis Endocytosis Facilitated Diffusion Exocytosis