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Adjustment to Metabolic Needs of Tissues

Adjustment to Metabolic Needs of Tissues - Metabolically...

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Adjustment to Metabolic Needs of Tissues Oxygen Unloading Metabolically active tissues consume oxygen to replace the energy used to do work. So metabolically active tissues have a lower P O2 than non-working tissues. At this lower P O2 , more oxygen will be unloaded from Hb. Using Figure 6 , at a P O2 of 20 mmHg, Hb is only 25% saturated (it has released 2 additional oxygen molecules to replenish the oxygen used by these tissues). Metabolically active tissues have increased temperatures and higher P CO2 levels -- at these higher temperatures and higher acidity , Hb will unload O 2 more readily (the curve shifts to the right) (see Figure 7 ). Other factors may increase oxygen unloading from Hb. The metabolite bisphosphoglycerate , which can be increased during fever and in response to hormonal activation, binds to Hb and causes HbO 2 to release O 2 . Figure 7 Carbon Dioxide loading
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Unformatted text preview: Metabolically active tissues also affect how the blood carries CO 2 . A small portion of total CO 2 will dissolve directly in the plasma of the blood. About 20 - 25% of the CO 2 carried by the blood will bind to Hb. Low levels of HbO 2 (during activity) enables the Hb to transport more CO 2 , known as the Haldane effect. HbO 2 does not bind to CO 2 as well as deoxyhemoglobin ; so the more O 2 that is unloaded from Hb, the more CO 2 can be bound to Hb. Furthermore, HHb binds more H + than HbO 2 which shifts the CO 2 + H 2 O --> H 2 CO 3--> HCO 3-+ H + reaction to the right enabling an increased conversion of CO 2 into carbonic acid and bicarbonate. The majority of CO 2 produced by the body will be converted into HCO 3-and dissolve in the plasma. This conversion changes the pH of the blood and can alter the respiratory rate....
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