Transport of carbon dioxide in the blood

Question 1

co2 and toxicity

Answer 1

waste product - generates H+
large changes in H+ conc if not buffered lead to significant changes in pH - altering teritary structures of proteins/enzymes

Question 2

co2 generated in resting person

Answer 2

metabolism generates ~ 200ml of co2 per minute

Question 3

co2 solubility

Answer 3

much more soluble in water than oxygen, so blood carries more dissolved co2 than o2
only 10% dissolves in plasma and erythrocytes - must be carried in other forms

Question 4

25-30% co2 molecules

Answer 4

react reversibly with amino groups of hemoglobin to form carbaminohemoglobin
CO2 + Hb HbCO2
deoxyhemoglobin has greater affinity for co2 than oxyhemoglobin

Question 5

60-65% co2 molecules

Answer 5

converted to HCO3-
CO2 + H2O H2CO3 HCO3- + H+
first reaction is rate limiting and very slow unless catalysed by enzyme carbonic anhydrase - present in erythrocytes, not plasma

Question 6

chloride shift

Answer 6

HCO3- moves out of erythrocytes and into plasma via a transporter which exchanges one HCO3- for one Cl-
maintains electroneutrality
favours above reaction to right

Question 7

total blood carbon dioxide

Answer 7

sum of amounts of dissolved carbon dioxide, HCO3- and carbaminohemoglobin

Question 8

co2 in systemic venous blood

Answer 8

blood Pco2 is higher than alveolar Pco2, so it diffuses from blood to alveoli
drives reactions to left
HCO3- and H+ combine to form H2CO3, which dissociates into H20 and CO2
HbCO2 generates Hb and CO2
this CO2 diffuses into alveoli