Hemoglobin and the Oxygen-Dissociation Curve (IB)

- "Partial Pressures" of O2 and CO2 are measurements of their concentrations

- As O2 binds, conformational change makes it easier for other O2's to join (4 in total, 4 heme groups per hemoglobin)

- As O2 leaves, makes it easier for other O2's to leave

- When CO2 is produced it diffuses into RBC, where it reacts with H2O and is converted into Carbonic Acid via carbonic anhydrase enzyme, ****the acid then dissociates into H+ and HCO3-

- The H+ ions made the blood more acidic which causes oxyhemoglobin to dissociate and release O2

- The HCO3- ions are pumped through the membrane of the RBC and into the plasma where they combine with Na+ to form NaHCO3

- To ensure that the RBCs remain uncharged, Cl- ions pass into them. This is known as the chloride shift!

- When the RBCs reach the lungs, the NaHCO3 combines with H+ to form H2O, CO2, and Na+

- The CO2 is then released from the body during exhalation

Partial Pressure of CO2

- As cells respire, the pO2 decreases, and the pCO2 increases

- An increase in the pCO2 causes Oxyhemoglobin to give up its O2 more readily

- This is because when the CO2 is converted to acid it produces H+ ions which lowers the pH of the blood

- The Oxyhemoglobin then dissociates, giving up its O2 so that the Hb can bind to the H+ ions to prevent a change in pH

- Therefore Hb acts as a buffer by taking up the H+ ions and forming "Hemoglobinic Acid"

BOHR EFFECT (shift in affinity graph)

- more oxygen released with increase in CO2 and lowering of pH levels

- as pCO2 increases, the dissociation curve shifts to the right & down

So Overall:

- When O2 diffuses into the lungs there is a high PP of O2, so it will load onto Hb forming Oxyhemoglobin

- The O2 is then carried in the blood to respiring cells that have a low pO2 and a high pCO2

- So the Oxyhemoglobin releases the O2 because of the low pO2 and ALSO because of the high pCO2 which causes a DROP in pH

- The O2 is used by cells for respiration and the Hb binds to the H+ ions to prevent changes in pH

The composition and O2 carrying capacity differs among organisms...

Leslie: http://www.interactive-biology.com/2643/061-the-bohr-effect/

Transport of Respiratory Gases: http://www.youtube.com/watch?v=Qrvrs6RXxwY

Biochem dude: http://www.youtube.com/watch?v=DgelvyH7iB8&feature=related