anim_gas_transport _answer_key.doc

Gas Transport To complete this worksheet, select: Module: Gas Exchange and pH Balance Activity: Animations Title: Gas Transport Introduction 1. Summarize blood’s role with regard to transporting oxygen and carbon dioxide. The blood serves as a medium for gas transport throughout the body. Oxygen is only available in the lungs. Because the partial pressure of oxygen is higher in the alveoli than in the blood, oxygen diffuses into the blood and is transported to the systemic cells. Cells generate carbon dioxide during metabolism and the blood transports the carbon dioxide to the lungs for removal. Oxygen Transport 2. Contrast the two ways oxygen is transported in blood. Dissolved in Blood Plasma Only about 3% of the oxygen is dissolved in the blood plasma. Bonded to Hemoglobin 97% of the oxygen is bound to hemoglobin in the form of oxyhemoglobin. 3. Describe the important role of the heme groups within each hemoglobin molecule. Hemoglobin consists of iron and 4 polypeptide chains. Each of the polypeptide chains contains an iron-bearing heme group. The heme group has an affinity for and binds to oxygen. 4. Define each of the following: deoxyhemoglobin –hemoglobin not bound with oxygen. oxyhemoglobin - hemoglobin bound with oxygen 5. What is the oxygen association reaction that occurs in the lungs? O2 + Hb-H Hb-02 + H+ 6. What is the oxygen dissociation reaction that occurs at the tissue cells? Hb-02 + H+ O2 + Hb-H Factors That Affect Hemoglobin’s Saturation With Oxygen 7. Name the factors that affect hemoglobin’s saturation with oxygen. Once completely saturated, the molecule is called oxyhemoglobin. The affecting factors are partial pressure of oxygen, partial pressure of carbon dioxide, BPG, hemoglobin type, pH and temperature. Oxygen-Hemoglobin Dissociation Curve 8. PO2 is a primary factor influencing the degree of hemoglobin saturation. Explain how PO2 in the lungs and tissue cells determines whether oxygen binding or dissociation occurs with hemoglobin. The partial pressure of oxygen is a primary factor influencing the degree of saturation of hemoglobin. The partial pressure of oxygen determines the number of oxygen molecules that can bind to dissociate from hemoglobin. As blood passes through the alveoli, the blood capillaries, oxygen will bind to all available sites of hemoglobin and form oxyhemoglobin because of the high PO2 in the alveoli space. Blood in vessels coming from the lungs is highly saturated with oxygen. When the oxygen rich blood reaches the tissues, where oxygen levels is low, oxygen detaches from the hemoglobin and is unloaded to the tissues. Hemoglobin’s Affinity for Oxygen 9. a. Describe the Bohr Effect. The Bohr effect addresses the effect of pH on dissociation of oxygen from hemoglobin. Increased metabolic acids enhance the dissociation of oxyhemoglobin and the unloading of oxygen. Low pH increases the unloading of oxygen to actively metabolizing cells. b. In contrast to the Bohr Effect, how does elevated pH affect hemoglobin’s oxygen affinity? Increasing pH increases the affinity of oxygen for hemoglobin thereby lowering the unloading of oxygen to the tissue cells. 10. a. Actively metabolizing cells aerobically use oxygen and produce carbon dioxide. Describe how increasing levels of blood carbon dioxide affect hemoglobin’s oxygen affinity? Where (in the body) does this occur? Carbon dioxide produced from metabolically active tissues binds with water and form carbonic acids which lowers the pH and decreases the affinity of oxygen for hemoglobin, thus promoting dissociation of oxygen from hemoglobin. This occurs at the cellular/tissue level and allows oxygen to be available for metabolizing cells. b. Explain CO2’s affect on oxygen loading in the alveolar spaces. Decreased carbon dioxide availability, as in the alveolar spaces of the lung, increases the affinity of hemoglobin for oxygen and promotes oxygen loading and transport. 11. Describe how body temperature affects O2 association with hemoglobin. Temperature has a limited effect of the association and dissociation of oxygen with hemoglobin. Under normal temperatures, hemoglobin’s ability is unaffected. However, at the metabolically active tissue level, blood temperature is increased and increases the thermal motion of molecules thereby promoting the unloading of oxygen fueling aerobically active cells. Explain the affect of BPG on O2 association with hemoglobin. BPG, or bisphosphoglycerate is a product of anaerobic metabolism and accumulates in RBC’s in low oxygen situations. Hormones such as thyroxin, human growth hormone and epinephrine as well as testosterone can increase the production of BPG. The higher the levels of BPG in the RBC, the more oxygen that is unloaded from the hemoglobin. Carbon Dioxide Transport 13. Name the three ways CO2 can be transported by the blood and the percentage for each mechanism. 23% bound to hemoglobin 7% dissolved in solution 70% as bicarbonate ions 14. Explain carbaminohemoglobin formation and function. Carbaminohemoglobin forms at metabolically active cells. Here CO2 + HbHb-CO2, At the lungs the CO2 dissociates from the hemoglobin molecule Hb-CO2 CO2 + Hb. Carbon dioxide diffuses out of the blood cell and into the plasma in the pulmonary capillaries and then enters the alveolar space. 15. a. Explain bicarbonate ion formation and how it is used to transport carbon dioxide. Carbon dioxide produced by cells diffuses into the RBC and combines with water. Under the influence of an enzyme, carbonic anhydrase, carbonic acid is formed which quickly dissociates into bicarbonate and free hydrogen ions. b. Define the chloride shift and explain why it occurs. The bicarbonate ions that are formed diffuse out of the red blood cell into the blood plasma. Negatively charged chloride ions move into the cell to balance the movement of the negatively charged bicarbonate ions out of the cell. This maintains the electrical balance in the cell.