Question

Carbon dioxide 

A. Is carried as carboxyhaemoglobin on the haemoglobin molecule.

B. Uptake by the blood increases its oxygen-binding power. 

C. Uptake by the blood leads to similar increases in H⁺ and HCO₃^-  ion concentrations. 

D. Stimulates ventilation when breathed at a concentration of 20 per cent. 

E. Content is greater than oxygen content in arterial blood.

Answer 1

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.