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bild2midtermreview - BILD2 Winter2009

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Review questions for Midterm 2 BILD 2 Winter 2009 What are the general principles of gas exchange? What are important features of respiratory surfaces? Explain how fish gills maximize the transfer of oxygen from water to blood. Gills are specialized outfoldings of a body surface for gas exchange; parallel tubes carry out exchange, opposite flow of blood and H2O. There is a diffusion gradient that favors the transfer of O2 to blood. Gills remove 80% of oxygen from H20. Water enters the fish’s mouth and flows perpendicular to the gill filaments: counter current exchange Filament structure: [O2 rich blood | lamelia | O2 poor blood] so from left to right, the O2 gradient is high to low. Water flow: ------------------ V V V V V -O2 Blood Flow ----------------- Describe the structure of the mammalian lung. Large surface area Air nose trachea 2 brochi bronchioles alveoli (where activity occurs) What is an aveolus and what does it do? Explain both structure and function. An alveolus is a thin walled air sac and the site of gas exchange. O2 is released into the circulatory system while CO2 is released into the lung. How do we breathe? (what are the mechanics of negative pressure ventilation?) Inhalation: diaphragm contracts (moves down) to expand the chest cavity; Rib cage expands as the rib muscles contract . Increases the volume in the lung so that the alveoli pressure is less than the atmospheric pressure. Exhalation: Volume decreases, air pushed out. Rib cage gets smaller, diaphragm pushed up. What is the definition of partial pressure? Partial pressure is the pressure of a component in a mixture of gases. Blood as high P CO2 and low P O2, so it exchanges with the lungs to give away off CO2 and take in O2. What are the differences between the partial pressure of oxygen and carbon dioxide in tissues vs. lungs? Tissue: low oxygen, high CO2 Lungs: high oxygen, lower CO2
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How is oxygen transported in the body? Oxygen is transported via Hemoglobin in the red blood cell Hemoglobin allows 4 oxygen molecules to bind to it. Draw out an oxygen dissociation curve for hemoglobin. What is cooperative binding? Cooperative binding: Oxygen binds to the first site in hemoglobin, changing its shape of the other subunits so that oxygen can bind to them. Raises oxygen affinity, reverse also happens. Why is this important for oxygen pick up and release? It raises/lowers oxygen affinity. Once one is loaded/unloaded, the three others are likely to follow How does pH affect oxygen binding and why? At a lower pH, hemoglobin is more likely to give up oxygen, so it shifts the curve to the right. HOMO. How is carbon dioxide transported in the blood? What happens in the lungs? At tissues? CO2 is produced in the tissues and diffuses into the blood. Some of it binds to hemoglobin, most of it is converted to HCO3- (bicarobate) The bicarbonate enters the plasma where it is transported to the lungs via a RBC. Inside the RBC, it is in the form of Carbonic Acid H2CO3. Then it is released into the lung as CO2.
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