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Option H. Gaseous Exchange Mrs. jackie Define partial pressure Diffusion of gas, whether present in air or dissolve in water depends on differences in a quantity called partial pressure Define as the pressure that one component of a mixture of gases would exert if it were alone in a container Example At sea level the atm exerts a total pressure of 760mm Hg. Since the atm s 21% oxygen the partial pressure of O2 is 0.21*760 or about 160mmhg. This is the portion of atmospheric pressure contributed by O2 hence the term atmospheric pressure. The partial pressure of CO2 is 0.23mmHg Partial Pressure continues When water is exposed to air the amount of gas that dissolves in the water is proportional to its partial pressure in the air and its solubility in water. An equilibrium is reach when gas molecules enter and leave the solution at the same rate At this point the gas is said to have the same partial pressure in solution as it does in the air. Explain the oxygen dissociation curves of adult and fetal hemoglobin and myoglobin. AS oxygen enters the blood stream by diffusing from the alveoli into the capillaries, it diffuses into red blood cells and combines with hemoglobin When hemoglobin takes the first molecule of oxygen, it takes the next one at a faster rate and the third one is taken even faster. This means that the affinity of hemoglobin to oxygen increases as it takes more and more oxygen This results in the curve relating the availability of oxygen to saturation of hemoglobin with oxygen to be sigmoidal. Explain the oxygen dissociation curves of adult and fetal hemoglobin and myoglobin. As shown in the graph The saturation of hemoglobin with oxygen increases as the partial pressure of oxygen increases. Hemoglobin become completely saturated at an oxygen partial pressure of about 100mmHg When the partial pressure of oxygen drops as in the case of the capillaries near the working tissues and cells, hemoglobin releases oxygen to the cells. Hence hemoglobin associated with oxygen with oxygen has a high PO2 as in the case of capillaries in the alveoli area, Its dissociates its oxygen when oxygen has a low P)2 as in the case of the capillaries in the area of body tissues and cells. The case of fetal hemoglobin Fetal hemoglobin curve is shifted to the left due to its higher affinity to bind with oxygen. The curve is shifted to the left which means that fetal hemoglobin has higher affinity to oxygen and so it associates with oxygen more readily. The case of myoglobin Myoglobin is the hemoglobin of muscles Its has greater affinity to oxygen and so its binds it with a high rate Is does not dissociate its oxygen unless the PO2 drops very low. It starts to release its oxygen when the muscle is exhaust Describe how carbon dioxide is carried by the blood including the action of carbonic anhydrase, chloride shift and buffering by plasma proteins. Carbon dioxide is carried in the blood as a bicarbonate ion. A small amount is carried by the amino groups of the polypeptides of hemoglobin. CO2 enters a red blood cell and reacts with water, resulting in the formation of carbonic acid. This molecules dissociates into hydrogen carbonate and hydrogen ions Describe how carbon dioxide is carried by the blood including the action of carbonic anhydrase, chloride shift and buffering by plasma proteins. Hemoglobin has a high affinity to oxygen and so its reacts with it a high rate, hence hemoglobin leaves its oxygen and takes up a hydrogen ion instead This frees oxygen molecules, and so they diffuse out of the blood cells into the liver cell which has lower concentration of O2 Carbonate ions build up and so they start to diffuse out into the plasma. In trade for these ions, chloride ions enter the red blood cell. This is called the chloride shift to maintain a normal distribution of ions. Describe how carbon dioxide is carried by the blood including the action of carbonic anhydrase, chloride shift and buffering by plasma proteins Carbonic anhydrase Converts carbon dioxide into bicarbonates and protons. Explain the role of the Bohr shift in the supply of oxygen to respiring tissues When oxygen enters the blood cell and carbon dioxide leaves the blood cell CO2 levels increases in the liver cell More CO2 diffuses into the blood cell and more O2 is released by hemoglobin Hence an increase of CO2 causes higher dissociation of oxygen to the cells A higher CO2 level causes the oxygen dissociation curve to shift to the right. This is called the Bohr shift. Explain the role of the Bohr shift in the supply of oxygen to respiring tissues Since a higher CO2 results in higher H When the acidity of the blood increase the graph is shifted to the right. This effect helps tissues get more oxygen since shifting to the right means more dissociation of oxygen to the tissues. Explain how and why ventilation rate varies with exercise When there are changes in carbon dioxide concentration there in a decrease in blood pH This is detected by chemosensor in the aorta and carotid arteries Chemosensors send impulses to the breathing center of the brain Nerve impulses are then sent to the diaphragm and the intercostal muscles to increase the concentration or relaxation rates.