2. Oxygen Transport in the blood  Not very soluble in fluids  Can be carried two ways –Physical solution, dissolved in the fluid portion of the blood –In combination with hemoglobin, an iron-protein molecule within RBC

3. @PO 2 of 100, 0.3 ml of gaseous oxygen dissolves in 100 ml of plasma, 3 ml/liter

4. @Q of 5 l/min, 15 ml of oxygen carried through body/minute  This would sustain life for about 4 sec  Random movement of dissolved oxygen establishes the PO 2 of the blood and tissue fluids  This pressure of dissolved oxygen establishes the PO 2 of the blood and tissue fluids  This pressure of dissolved oxygen is important in the regulation of breathing  It also determines the loading and subsequent release of oxygen from hemoglobin in the lungs and tissues (respectively)

5. Oxygen combined with hemoglobin  Increases oxygen carrying capacity 65-70 times  For each liter of blood, 19.7 ml of oxygen are captured (temporarily) by hemoglobin  Each of the four iron atoms in the hemoglobin molecule can loosely bind one molecule of oxygen  Hb 4 + 4O 2 ↔ Hb 4 O 8

6.  Requires no enzyme  Occurs without a change in the valance of Fe ++ (as would be found in oxidation)  The oxygenation of hemoglobin to oxyhemoglobin depends entirely on the PO 2 in the solution

7. Oxygen-carrying capacity of Hemoglobin  Males have 15-16 g of Hb/100 ml of blood  Females have 5-10% less, about 14 g/100 ml  Gender difference may account for some lower values in maximal aerobic capacity even after differences in body fat and size are accounted for  Each gram of Hb can combine loosely with 1.34 ml of oxygen  If Hb content of blood is known, the oxygen carrying capacity can be calculated:  Blood’s capacity = Hb X O 2 capacity of Hb

8.  20 ml/O 2 /100 ml = 15 X 1.34 O 2 /g  Usually ~20 ml of oxygen is carried with Hb in each 100 ml of blood when Hb is fully saturated  If there are significant decreases in Fe in the RBC, decreases in the oxygen-carrying capacity of the blood, decrease the ability to sustain mild aerobic capacity (anemia)

9. PO 2 in the lung  Hemoglobin is about 98% saturated with O 2 at alveolar PO 2 of 100 mm Hg  Therefore, each 100 ml of blood leaving the alveolus has about 19.7 ml of O 2 carried by hemoglobin  Remember, 0.3 ml of oxygen is dissolved in the plasma component of the blood  This plasma PO 2 regulates the loading and unloading of Hb

10. O 2 dissociation curve (Oxyhemoglobin dissociation curve)  Saturation of Hb changes little until the pressure of oxygen falls to about 60 mm Hg  This flat, upper portion of the oxyhemoglobin dissociation curve provides a margin of safety  @~75 mm Hg (altitude or lung disease) saturation is lowered by ~ 6%  If PO 2 is lowered to 60 mm Hg, hemoglobin is still 90% saturated

11. PO 2 in the tissues  Differences in oxygen content of arterial and mixed venous blood is the arteriovenous difference, or the (a-v)O 2 difference  @ rest (a-v)O 2 difference is ~4-5 ml of oxygen/100 ml of blood  Large amounts of oxygen remains bound to the hemoglobin, providing a reserve  This reserve can provide immediate oxygen, if the demand suddenly increases

12.  When the cells need O 2 (exercise), the tissue PO 2 lowers, leading to a rapid release of a large quantity of oxygen  During vigorous exercise, extracellular PO 2 decreases to about 15 mm Hg, only 5 ml of O 2 remain bound to Hb  (a-v)O 2 difference increases to about 15 ml of O 2 /100 ml blood

13.  If tissue PO 2 falls to 3 mm Hg during exhaustive exercise, almost all of the oxygen is released from the blood that perfuses the active tissue  Without any increase in local blood flow, amount of O 2 released to muscles can increase almost 3X above resting, due to more complete unloading of Hb  A working muscle can extract 100% of O 2