8 Respiration 3 Gas transport in Blood

8 Respiration 3 Gas transport in Blood - 2 O than O 2 is....

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Respiration I. Gas exchange A. Cellular versus organismal B. Requirements for organismal gas exchange C. Diffusion of gases in air versus water II. Respiration in animals via specialized organs: A. Gills B. Lungs - structure and ventilation III. Gas transport in blood
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Gas Transport in Blood Problem: O 2 is not very soluble in water (0.7%) compared to air (21%) How can enough O 2 be transported in blood? Solution: Instead of transporting dissolved O 2 , blood transports O 2 bound to respiratory pigments like hemoglobin. Hemoglobin exhibits cooperative binding via allosteric interactions Heme group Iron atom O 2 loaded in lungs O 2 unloaded In tissues Polypeptide chain O 2 O 2
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O 2 unloaded to tissues at rest O 2 unloaded to tissues during exercise 100 40 0 20 60 80 0 40 80 100 O 2 saturation of hemoglobin (%) 20 60 Tissues during exercise Tissues at rest Lungs P O 2 (mm Hg) (a) P O 2 and hemoglobin dissociation at pH 7.4 Fig. 42.29a - Oxygen Dissociation Curve for Hemoglobin • Cooperative binding of O 2 to hemoglobin results in S-shaped curve.
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Fig. 42.30: CO 2 transport in blood • CO 2 is more soluble in H
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Unformatted text preview: 2 O than O 2 is. 7% of CO 2 released by cells is transported as dissolved CO 2 . 23% of CO 2 released by cells binds to Hb (on amino groups, NOT on heme group). 70% of CO 2 transported as bicarbonate ion. CO 2 + H 2 O <-> H 2 CO 3 <-> H + + HCO 3-(carbonic acid) (bicarbonate) Bicarbonate Reaction: Diffusion determines the direction of the bicarbonate reaction. H + released or consumed during bicarbonate reaction result in lower pH (higher [H + ]) in active tissues. Fig. 42.29b: The Bohr Shift O 2 saturation of hemoglobin (%) 40 20 60 80 40 80 100 20 60 100 P O 2 (mm Hg) (b) pH and hemoglobin dissociation pH 7.4 pH 7.2 Hemoglobin retains less O 2 at lower pH (higher CO 2 concentration) The O 2 dissociation curve for Hb shifts to the right at lower pH because [H + ] affect the conformation of Hb. Lower pH in active tissues allows more O 2 to be released in these tissues for the same pO ....
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8 Respiration 3 Gas transport in Blood - 2 O than O 2 is....

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