Carbon Dioxide in the Blood Flashcards
How much more CO2 is there in arterial blood than O2?
2.5 times as much
What is the role of CO2 in the arterial blood?
Not present as a waste product
Used as a buffer to control pH
Reacts with water = carbonic acid (H2CO3) = H+, HCO3 (bicarb)
What is the normal range for pH?
7.35-7.45
How does carbon dioxide react in plasma?
CO2 + H20 < —- > H+ + HCO3-
Reversible
Determines pH
What happens if pCO2 rises?
pH falls = more acidic
What happens if pCO2 falls?
pH rises = more alkaline
The amount of CO2 dissolving in the blood depends on what?
Partial pressure of CO2
Rate of breathing
Where does the high levels of bicarb in the blood come from?
Dissociating CO2
Production in RBCs
What is the henderson-hasselbalch equation?
Calculate pH of plasma
pH = pk + log ( [HCO3] / (pCO2 x 0.23) )
What enzyme is present in RBCs that allows for high production of HCO3?
Carbonic anhydrase
Reaction proceeds in the forward direction because H+ is mopped up by Hb
The amount of HCO3 that RBCs can produce is dependent on what?
Levels of binding of H+ to Hb
What determines the pH of arterial blood?
Ratio between [HCO3] and pCO2
1) rate of breathing = level of CO2 present
2) kidney excretion = level of HCO3 present
How does the venous blood give up the correct amount of CO2 to the lungs?
Hb picks up O2 = R state = gives up extra H+ = H+ reacts with HCO3 = CO2 to be breathed out
The amount of H+ bound the Hb depends on what?
More O2 = R state = less H+ bind Hb (lungs)
Less O2 = T state = more H+ bind Hb (tissue)
How can venous blood transport more CO2?
Less O2 = Hb T state = more H+ bind Hb
More H+ that binds Hb = more HCO3 prod = more CO2 being carried in its reacted form
