Homework2key_001FA07

Homework2key_001FA07 - BILD 2 FALL 2007 Homework#2 Dr Towb...

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BILD 2 FALL 2007 Dr. Towb Homework #2 10/12/07 1) Water can hold only about 5ml dissolved oxygen/liter at body temperature, yet our body can use 2 liters dissolved oxygen/minute during intense exercise. How does our body manage this? Rather than simply dissolving oxygen in the blood plasma, oxygen is transported with the use of the respiratory pigment – hemoglobin, contained within erythrocytes (essentially bags of hemoglobin). Hemoglobin can bind oxygen directly and reversibly, increasing the amount of oxygen the blood can deliver to about 200ml O 2 /L. 2) Where might countercurrent exchange systems be found, and what do they do? Explain how one works with the aid of a diagram. Countercurrent exchange systems can be found in the circulatory system of fish as well as in the thermoregulation of some endothermic marine mammals and birds. The countercurrent exchange system in fish gills is a very efficient means of extracting O 2 from the surrounding water in which little O 2 is dissolved. In this system, water is drawn in through the mouth and past the gills in the opposite direction of the blood flowing through the vessels. This causes the blood to encounter water with even higher O 2 concentrations as it moves past the gills, resulting in the continuous accumulation of O 2 in the blood. BLOOD WATER High [O] 2 Low [O] 2 Low [O] 2 Lowest [O] 2 Higher [O] 2 High [O] 2 Or, another answer: The countercurrent exchange system in the thermoregulation in marine mammals and birds prevents excessive heat loss by diverting heat in blood away from the body’s surface where heat
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Homework2key_001FA07 - BILD 2 FALL 2007 Homework#2 Dr Towb...

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