lec 21.docx

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Biological Sciences
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Peter A.Bowler

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e109 11/21/12 Physiology in the news LanceArmstrong “doping”—accused of using Erythropoietin (EPO) to increase his number of red blood cells in his circulatory system, which carry oxygen. -Lance implemented a number of means to avoid detection of EPO use: 1. microdosing: using smaller amounts of EPO to reduce the clearance time of the drug 2. intravenous injections: injecting the drug directly in the vein rather than subcutaneousy to reduce clearance time 3. saline, plasma or glycerol infusions if your hematocrit is unusually high (over 50%) 4. Blood transfusion/blood doping: extraction of an athlete’s own blood pre-competition and re- infusion of that blood shortly before or during competition to increase the athlete’s oxygen carrying red blood cells + by increasing the number of circulating red blood cells, transfusions increase the oxygen carrying capacity of the blood and enhance endurance and recovery (raises the supply of oxygen available to your muscles) +increases the volume of the blood in your system—inject back in a higher hematocrit (greater volume fraction of red blood cells)—increasing the hematocrit with your own red blood cells Effect of pH Fig 18-9 pH 7.4 = normal (partial pressure of oxygen around 22 mmHg for normal binding curves=unload about 40% of the oxygen) If the pH is slightly higher or lower, this changes the binding affinity of the hemoglobin to the oxygen Shifting the curve to the right facilitates the unloading of oxygen from Hemoglobin (a more acidic environment facilitates unloading); if the pH is lower (more acidic), the percent oxygen saturation of hemoglobin is lower and therefore holds onto less oxygen and unloads more of it to the tissue cells. pH changes based on local conditions (100 mmHg for lungs and 20 mmHg for the tissues) Clicker question: At higher temperatures, oxygen loading in the lungs is facilitated (greater/made easier). False b/c the saturation is lower. This means that oxygen loading is not facilitated or made easier/greater at higher temperatures. Clicker question: At higher temperatures, oxygen unloading in the tissues is facilitated. True Chronic hypoxia leads to increase in 2,3-DPG in red blood cells 2,3-DPG occurs inside red blood cells (where the hemoglobin is) that affects oxygen- hemoglobin binding (2,3-DPG does not cross the cell membrane) If there’s no 2,3-DPG at all in the vicinity of hemoglobin in a red blood cell, the oxygen is bound much more tightly to hemoglobin and much harder to come off -Chronic hypoxia: long-term exposure to lower levels of oxygen; can result from exposure to high altitude (total pressure is less up there, so the partial pressure of oxygen is lower) = increase in level of 2,3-DPG and EPO at higher altitudes in your red blood cell -The shifting of a curve to the right facilitates the unloading of oxygen from hemoglobin from the tissues Clicker question: At higher Partial pressure of CO2, oxygen loading in the lungs (at Partial pressure = 100 mmHg is facilitated) False b/c it’s same or less but NOT more oxygen unloading facilitated Clicker question: At higher Partial pressure of CO2, oxygen unloading in the tissues (at partial pressure of oxygen =40 mmHg) is facilitated. True Fetal hemoglobin vs. Maternal hemoglobin -Fetal hemoglobin: the fetus does not have direct access to the oxygen in the environment; +can only get oxygen from mom’s blood supply from the placenta +oxygen will move FROM mother’s blood to baby’s blood (as the two are brought into close proximity in the placenta) down its partial pressure gradient +Fetal hemoglobin has a greater affinity for oxygen, so oxygen will move from mother’s
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