Gas Exchange

How Does Air Enter Our Bodies? -Trachea -Enters the Bronchial tree -Tubes become increasingly smaller -Final destination: alveoli

What Are Alveoli? Tiny Air sacs in lungs (300 Million of them) Surface Area is equivalent to a tennis court. The alveoli is the primary location of gas exchange. Capillaries (blue and red) wrap around alveolar sac. Alveoli is where air meets blood.

How is Gas Exchange Possible? Simple Diffusion. Diffusion does not occur along concentration gradient. Gas exchange is made possible by Pressure Gradients

Pressure Gradients? When discussing movement of gases, a more applicable way of measuring gradients is to use pressure gradients, not concentration gradients. These pressure gradients are the result of Partial Pressure. As molecules run into the walls with the energy inherent in them, pressure is created.

So How do Pressure Gradients Relate to Gas Exchange? The Pressure gradient created from the partial pressure in the alveoli prompts simple diffusion from the alveoli to the capillaries. http://www.youtube.com/watch?v=DoSTehS7iq8&feature=player_embedded The air we breathe consists of Oxygen, Nitrogen, Carbon Dioxide, and Water vapor. Because Oxygen and Carbon Dioxide are small, polar, molecules, they are able to passively diffuse.

But Wait, There’s a Problem Oxygen and Carbon Dioxide cannot dissolve in blood These molecules need assistance from Hemoglobin Hemoglobin is a, “protein-based component of red blood cells,” responsible for the transport of oxygen. Oxygen becomes bound to the Heme groups of the hemoglobin. One atom of Iron in the center of each heme attracts and binds the oxygen. Oxygen binds to each heme site (four of them)

Anemia Anemia can be though of as “Iron poor blood.” The lack of iron in blood results in less oxygen being transported. (Recall that oxygen binds with hemoglobin by its attraction to Iron.) Symptoms of Anemia are feeling cold, dizzy, and irritable. Cures: Iron rich foods such as asparagus, Squash, bananas

Carbon Dioxide Transport 10% remains in blood 30% binds with hemoglobin to form Carbamino Hemoglobin (HbCO2) 60% is transported as bicarbonate (HCO3-) CO2 + H20 yields H2CO3 yields HCO3- Carbonic Acid Bicarbonate This reaction only occurs 1 in 1,000 times in blood. Carbonic Anhdrase increases this reaction number by 250 times. The rapid rate of conversion from CO2 HCO3- reduces CO2 in blood and maintains the gradient to prompt further diffusion of CO2 into blood to be converted.

Bibliography Unknown, . "Anemia." Medline Plus. 12 Nov 2009. National Heart, Lung and Blood Institution, Web. 6 Nov 2009. <http://www.nlm.nih.gov/medlineplus/anemia.html>. Pollick, Michael. "What is Hemoglobin?." Wise Geek. Conjecture Corporation, Web. 6 Nov 2009. <http://www.wisegeek.com/what-is-hemoglobin.htm>. "REVIEW OF PARTIAL PRESSURE." RESPIRATION PHYSIOLOGY: ALVEOLAR GAS EXCHANGE. 2004. AC Brown, Web. 6 Nov 2009. <http://www.acbrown.com/lung/Lectures/RsAlvl/RsAlvlPrtl.htm>.