A. False It is carried as carbamino hemoglobin; carboxy hemoglobin is the combination of hemoglobin with carbon monoxide.
B. False It decreases as the oxygen dissociation curve is shifted to the right.
C. False HCO3- ions increase more; H+ ions are largely buffered by hemoglobin.
D. False Breathing 20 per cent CO2 causes respiratory depression; stimulation of respiration by CO2 is maximal when breathed at concentrations of around 5 per cent.
E. True CO2 content in arterial blood is about 500 ml/l; O2 content is about 200 ml/l.