B6A6GasExchange

B6A6GasExchange - Gas Exchange WHY RESPIRE? Gas Exchange in...

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Gas Exchange Heyer 1 Gas Exchange Gas Exchange in Animals in Animals WHY RESPIRE? • Mitochondria need O 2 to make ATP. C 6 H 12 O 6 + O 2 Ë CO 2 + H 2 O + Energy ATP • CO 2 by-product must be removed “Organismal Respiration” vs. “Cellular Respiration” • External gas exchange: ÿ environmental gases / tissues • Internal gas exchange ÿ tissues / tissues q Cell membranes are permeable to simple diffusion of dissolved O 2 and CO 2 • Cellular Respiration: using the oxygen to drive ATP production – The more cells (more body mass), the more O 2 needed ( oxygen demand ) SIZE MATTERS cutaneous exchange (protozoans, sponges, cnidarians, flatworms) flowing over surface • Surfaces must be moist for exchange to occur! SIZE MATTERS Size of rice grain Newborn Julia Creek Dunnart get 90% of O 2 from skin. v Size matters! v So does activity level. v Larger, faster animals need tricks to speed up exchange of gases How do animals get enough O 2 ?
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Gas Exchange Heyer 2 Diffusion of Dissolved Gases FICK’S LAW • GILLS vs. LUNGS • AQUATIC RESPIRATION • TERRESTRIAL RESPIRATION • RESPIRATORY PIGMENTS FICK’S LAW Fick’s law of diffusion of a gas across a fluid membrane: Rate of diffusion = KA(P 2 –P 1 ) / D Wherein: ß K = a temperature-dependent diffusion constant. ß A = the surface area available for diffusion. ß (P 2 –P 1 ) = The difference in concentration (partial pressure) of the gas across the membrane. ß D = the distance over which diffusion must take place. Adolf Fick, 1858 FICK’S LAW Fick’s law of diffusion of a gas across a fluid membrane: Rate of diffusion = KA(P 2 –P 1 ) / D Therefore, since: ß The diffusion is of dissolved gases across a fluid membrane ÿ The respiratory surface must stay wet! FICK’S LAW Fick’s law of diffusion of a gas across a fluid membrane: Rate of diffusion = KA(P 2 –P 1 ) / D Therefore, since: ß K = a temperature-dependent diffusion constant. ÿ Temperature is important! FICK’S LAW Fick’s law of diffusion of a gas across a fluid membrane: Rate of diffusion = KA(P 2 –P 1 ) / D Therefore, since: ß A = the surface area available for diffusion. ß D = the distance over which diffusion must take place. ÿ How can gas exchange rate be increased? ÿ Increase surface area and decrease thickness of respiratory surfaces as much as possible!
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This note was uploaded on 09/02/2011 for the course BIOL 6a taught by Professor Staff during the Fall '10 term at DeAnza College.

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B6A6GasExchange - Gas Exchange WHY RESPIRE? Gas Exchange in...

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