Bicarbonate is the major form of carbon dioxide at normal pH.Combines with water to form carbonic acid, and hydrogen and bicarbonate ions.Carbon dioxide transport in the blood (fig 13-9).Curves shift right, indicating a decreased hemoglobin-oxygen affinity.Sigmoidal shape reflects the subunit cooperativity (first molecule of oxygen has a harder time binding).Oxygen dissociation curves (fig 13-4) demonstrate the % saturation as a result of the partial pressure of oxygen.
Because capacity differs among individuals, content is expressed as % saturation.Content is equal to the amount of oxygen in solution (a very small portion) plus the bound oxygen).Capacity is equal to content when the blood is saturated (all sites are bound to oxygen).carboxyhemoglobin - carbon monoxide is bound (200 x greater affinity that oxygen).hemoglobin - four oxygen molecules bind to four heme units.oxygen has a higher solubility at lower temperatures.some fishes don't have respiratory pigments, but they live in arctic waters.3% volume w/out hemoglobin, 20% volume with hemoglobin Combine with oxygen to increase the blood oxygen content.Increased metabolism means more aerobic enzymes, more cristae, and mitochondria.Rates of exchange are dependent on metabolism.Diffusion of gases across capillary walls (to / from blood and cells).Insects use a tracheal system, allowing direct exchange with tissues (no blood needed).High carbon dioxide concentration in systemic veins, pulmonary arteries.High oxygen conc in systemic arteries, pulmonary veins.Large surface area (human lungs 50-100 square meters).Diffusion of oxygen and carbon dioxide across the respiratory epithelium.Keeps a large diffusion gradient across the shortest possible distance.Fresh supply of air/water at respiratory surface.
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