Oxygen Transport

Oxygen Transport - is not a simple linear one The loading...

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Oxygen Transport Henry's Law states that the solubility of a gas in a fluid is determined by how easily the gas dissolves in the fluid and the concentration of that gas at the air-water interface. The solubility coefficient of a gas in a specific fluid is immutable ; however, the partial pressure can easily change. The concentration of O 2 in arterial blood is about 20 ml/dl . 98.5% of that O 2 is bound to hemoglobin while 1.5% is dissolved in the plasma of the blood. Recall that each hemoglobin protein can bind to 4 O 2 molecules (4 O 2 /Hb). Hemoglobin bound to oxygen is called oxyhemoglobin , while hemoglobin not bound to oxygen is called deoxyhemoglobin . We can measure how much O 2 is bound to hemoglobin at different concentrations of oxygen and illustrate this information graphically. This is known as a oxyhemoglobin dissociation curve (see Figure 6 ). Figure 6 The relationship between hemoglobin saturation and P O2
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Unformatted text preview: is not a simple linear one. The loading of hemoglobin with oxygen displays cooperative binding or positive feedback. Binding with O 2 molecules causes the Hb to change shape; this shape change facilitates additional O 2 binding. The oxyhemoglobin dissociation curve shows that at the P O2 found in the alveoli (about 104 mmHg), Hb is ~100% loaded. This can be restated as: hemoglobin leaves the lungs fully saturated with oxygen (4 O 2 /Hb). At the P O2 found in the tissues (about 40 mmHg), O 2 dissociates from Hb, but as can be seen from the graph, Hb is still 75% saturated. Only 25% of the O 2 dissociates from Hb at normal P O2 of tissues. Hb has released only one O 2 molecule and three more are theoretically available. This provides the blood and tissues with a reservoir of oxygen that can be released when needed. The metabolic needs of the body can change the unloading of O 2 ....
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