PHIS 206 Lecture Notes - Lecture 18: Carbonic Anhydrase, Acidosis, Hypercapnia
2 May 2018
School
Department
Course
Professor
Lecture 18: Gas Transport and Regulation
Exchange Explanation
• Diagram
• Blood that leaves the lungs looks like the lungs (fresh air, not used), blood that’s leaving
the tissues looks like the tissues (stale, dry, etc) → exchange
• Venous blood = high CO2 levels, low O2 levels
• Arterial blood = high O2 levels, low CO2 levels
Oxygen Carrying by Hemoglobin
• Hemoglobin-O2 Binding
o Hb can bind 4 O2 molecules
o Typically, only the 4th of 4 O2 molecules dissociates in a trip around the
bloodstream
o A minor amount of O2 is carried in a simple dissolved form
o ANY MOLECULE OF HEMOGLOBIN CAN CARRY 4 O2
o Even though hemoglobin can carry 4 oxygens, it only lets 1 go (only offloads the
last one) → when Po2 of blood is 40 (reasonable, normal breathing)
o More o2 can come off if you’re near death or other extreme measures
o Oxygen has to come off the hemoglobin to be able to be used
Oxygen Pickup and Alveolar Air
• The air in the alveoli (alveolar air) has a rather constant level of O2 during breathing
cycle
• Blood arriving in the pulmonary capillaries equilibrates with this alveolar air
• w/o hemoglobin, we do not have the ability to carry enough oxygen to live
Shift
• Change in Affinity
o Leftward Shift → Like
o Rightward Shift → Release
o Oxygen bound to Hb can’t reach the tissues → rightward shifts are beneficial
• PO2 of 100, we are fully saturated
• We expect about a PO2 of 70 or 75 (don’t really remember)
• Leftward shift, hemoglobin likes oxygen more - binds stronger?
• Rightward shift, hemoglobin more readily releases oxygen
• Rightward shift could be triggered by increase in acidity, ….. On graph
CO2 Transport
• Three methods of transport of CO2 in the blood:
o Dissolved CO2 (about 5%)
o CO2 bound to proteins in RBC or plasma (about 20%)
o CO2 carried as bicarbonate (HCO3^-) (about 75%)
• Carbonic anhydrase = fastest enzyme in your body
find more resources at oneclass.com
find more resources at oneclass.com
