at alveoli, how are o2 and co2 exchanged?
rapid simple diffusion (high to low [ ])
pressure of an individual gas in a mixture proportional to [ ] = %xtotal air pressure (ex % of 760 mmHG)
atm air is a mixture of
79% nitrogen 21% oxygen .04% co2
henrys law for gases in solution...
the higher the solubility, the less pp the gas exerts PP=[ ] dissolved gas/solubility
gas diffusion rate is inversely proportional to
mol weight of gas diffusion distance
gas diffusion rate is directly proportional to
difference in pp solubility of gas in fluid surface area of fluid T of fluid
solubility coefficient for O2
SOLUBILITY COEFFICIENT FOR co2
.57 20x more soluble than o2 (.024)
blood to transport 30-100x more O2 than could be carried as dissolved gas
how much o2 is carried on Hb and how much is dissolved in blood?
Hb - 97% dissolved - 3%
2 alpha and 2 beta chains, each has a heme group with a central iron that reversibly binds O2
1 o2 atom binding increases binding affinity for additional molecules in Hb chain heme groups
increased CO2 leads to increased H+[ ] leads to greater release in oxygen (less hb affinity) at peripheral tissues (occurs in exercise)
when do you see bohr effect?
Hb oxygen binding is inversely related to
acidity and [co2]
to decrease oxygen affinity, -[H+] -[co2] -T -23BPG
increase them all
rbc chloride content is higher in venous circulation than arterial because the bicarbonate-chloride ion echanger transports bicarbonate into blood plasma and chloride ions into rbc
oxygen binding to Hb causes co2 to be released from blood ---- reversal of bohr -- allows o2 to be picked up oxygen makes hb more acidic --> Hb releases H H combines w bicarbonate to make carbonic acid --> water co2
henderson hasselbach eq
determines pH of solution from pCo2 and HCO3 pH = pK + log ([HCO3]/(s x pCO2)
rbc enzyme that catalyzes rxn of co2 and water to form bicarbonate and H - occurs in venous blood
resp. acidosis vs alkalosis
acidosis - pco2 rises due to suppression of ventilation or decreased perfusion (ards and anesthetic) alk - pco2 decreases due to increased ventilation (aspirin, high altitude)
what compensates for respiratory pH changes?
how does renal system compensate in acidosis? alkalosis?
acidosis - increases HCO3 to return to normal pH alk - renal function decreases HCO3-
bicarbonate buffer system
keeps blood plasma pH within small range (7.37venous - 7.41 arterial) despite CO2 changes acid-base homeostasis using carbonic anhydrase