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Flap 2 |
| O2 transport | oxygen is transported in blood in two ways:
dissolved in plasma (only 1.5% because O2 is poorly soluble in plasma)
bound to hemoglobin inside RBCs (98.5% is carried this way)
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| Hemoglobin | hemoglobin (Hb) is a protein composed of 4 polypeptide chain subunits
each subunit is bound to an iron-containing heme group
since iron ions serve as oxygen-binding sites, each hemoglobin can rapidly and reversibly bind 4 oxygen molecules
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| Hemoglobin II | a hemoglobin molecule bound with oxygen is called oxyhemoglobin (HbO2)
a hemoglobin molecule that has released its oxygen is called deoxyhemoglobin (HHb)
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| Hemoglobin and Oxygen Transport | when the first oxygen molecule binds the first iron molecule, the hemoglobin changes shape and the affinity for the other 3 oxygen molecules progressively increases |
| Hemoglobin and Oxygen Transport II | similarly, when the first oxygen is unloaded, the affinity for oxygen is decreased and it becomes progressively easier for the other 3 oxygen molecules to dissociate from the hemoglobin |
| Hemoglobin and Oxygen Transport III |
hemoglobin is fully saturated when all four heme groups are bound to oxygen
if fewer than all four heme groups are bound, the hemoglobin is said to be partially saturated
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