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Carbon dioxide and Oxygen transport. Oxygen Transport. Oxygen is transported in the blood by hemoglobin in the red blood cells (RBC) Hb + O 2 --> HbO 2 (oxyhemoglobin) Recall: hemoglobin is a tertiary protein (4 globular proteins) bound to heme (iron pigment).
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Oxygen Transport • Oxygen is transported in the blood by hemoglobin in the red blood cells (RBC) • Hb + O2 --> HbO2 (oxyhemoglobin) • Recall: hemoglobin is a tertiary protein (4 globular proteins) bound to heme (iron pigment)
Carbon dioxide is carried in the blood three ways • ~70% is carried as the bicarbonate ion (HCO3-) • Dissolved in the plasma • Bound to hemoglobin (in RBC) as carbaminohemoglobin.
Bicarbonate ion • H2O + CO2 --> H2CO3 --> H+ + HCO3-
Carbaminohemoglobin • Hb + CO2 --> HbCO2 • Binds to a different site than oxygen, but changes the shape of the protein so that less O2 can bind to the Hb • If high [CO2] and low pH, then CO2 binds and O2 is released. • If low [CO2] and high pH, then CO2 is released and O2 binds to hemoglobin.
Gas Exchange • External Respiration (in lungs) • Gas exchange between alveolar air and blood • O2 and CO2 move by diffusion with the pressure gradient (high to low) • PO2 in air > PO2 in capillaries • PCO2 in air< PCO2 in lungs
What does that mean in terms of Hb? Bicarbonate equilibrium?
2. Internal Respiration • Gas exchange between blood capillaries and tissues • PO2 in blood > PO2 in tissues • PCO2 in tissues > PCO2 in blood • H+ combines with Hb in blood --> HHb (reduced Hb)
What does that mean in terms of Hb? Bicarbonate equilibrium?