Topic 2 The Respiratory System: Chemistry of Gas Exchange

Question 1

• Has 4 polypeptide subunits with each hosting a heme cofactor (organic molecule with iron atom in center)
• Each iron atom binds with one O2 molecule
• Exhibits cooperativity: when one O2 binds, the rest of the O2 molecules bind easier
• When one O2 is released, the rest are released easier

Answer 1

1. Hemoglobin

Question 2

• Lungs are O2 rich and want to hang on to it, but the tissues are O2 poor (lower O2 pressure) so hemoglobin will release O2 to tissues

Answer 2

2. As O2 pressure increases, O2 saturation of hemoglobin increases

Question 3

• Oxygen dissociation curve shows percentage of hemoglobin bound to O2 at various partial pressures of O2
• Curve shifted right (O2 released easier) when an increase in CO2, decrease in pH, increase in 2,3-DPG, or increase in temp
• Bohr Effect: Hemoglobin binding affinity decreases under conditions of low pH (high CO2/high H+) which leads to O2 loads released by hemoglobin since both O2 and H+ compete for hemoglobin binging sites

Answer 3

3. O2 saturation of hemoglobin also depends on CO2 pressure, pH, and temperature of blood

Question 4

• Chloride shift occurs to balance bicarbonate entering and leaving cell
• Carbonic anhydrase is in RBCs so at the tissues, to balance bicarbonate diffusing out of the cells, Cl- enters

Answer 4

Note