Question

Explain the movement of O2 and CO2 in each of the following locations below. Explain in terms of partial pressure (general, do not need to know exact numbers!) and the physiological reasons behind the differences in pressure/movement. (6 pts) a. At the lung capillaries (external respiration) b. At the body tissues

Answer 1

-CO2(in dissolved form) cozK Slow CO2 + H2O <-----H2CO3 <-----HCO3- + H coz of HCO3- reverse In the lungs hemoglobin get oxygenated. This oxyhemoglobin remove CO2 from carbiaminohemoglobin and also removes H+ from the Hb. The H+ which is removed in this, is added to HCO3- thus carbonic acid is produced. This carbonic acid in the presence of carbonic anhydrase or in its absence is converted to CO2 and H20. Thus the released CO2 from the blood goes to the alveoli. This occurs because pCO2 of the venous blood is 45mm Hg and that of the alveoli is 40mmHg so that CO2 can easily diffuse through the membrane While O2 transport can be; - - In physically dissolved form as the po2 of the alveoli is 104mmHg while that of the arterial blood is 100mmHg. Thus 02 can easily diffuse through the membrane from alveoli to blood - In RBC O2 is mainly transported as combining with the Hb. At the po2 of 100mmHg, 97.5% of Hb is saturated with O2 and the maximum amount of O2 carried by 1g of Hb is 1.34ml coef of fast chloride shift CO2 + H2O <----H2CO3 <-----H+ + HCO3- carbonic anhydrase Cl- CO2 + H2O <----HbCO2(carbamino hemoglobin) 02 02 + HHb -------> HbO2 + H+

CO2 (PCO2 = >50mmHg) CO2(PCO2 = 45mmHg, so diffuses) slow CO2 + H2O ------> H2CO3 ------> H+ + HCO3- CC In the blood pO2 is 100mmHg in arterial blood and that in the tissue is more than 30mmHg so that 02 diffuses to the tissue Also the pCo2 of the blood is 45mmHg in the venous blood and pCO2 is in the tissue is more than 50mmHg so that CO2 will diffuse to the blood from the tissue CO2 in the RBC combine with Hb to form carbaminoHb Also combine with water to form carbonic acid, which then dissociates to H+ and HCO3-. The H+ combine with Hb to form HHb coz CO2 + H2O fast--> H2CO3 -----> H+ + HCO3- carbonic anhydrase CO2 + Hb <---------> HDCO2 CO2 HBO2 -----> O2 + Hb (PO2 = >30mmHg) 02 s 02 (pO2 = 100mmHg) arterial blood so that 02 get diffuse to the tissue

to maintain the pressure difference in the body the gases are transported across the body