Transport of Carbon Dioxide MCQ - Practice Questions with Answers

1) Nearly 20-25 percent of CO2 is transported by RBCs:

• The carbon dioxide that enters the RBCs forms a reversible compound with an amino group (NH2) of the globin part of haemoglobin.
• The compound so formed is called carbaminohemoglobin. 

2) 70 percent of it is carried as bicarbonate:

• In the RBCs, a zinc enzyme carbonic anhydrase speeds up the formation of carbonic acid.
• Carbonic acid is a weak acid and quickly dissociates into hydrogen and bicarbonate ions.
• The hydrogen ions are buffered by the haemoglobin to form the haemoglobinic acid.
• As bicarbonate ions accumulate in the RBCs, some of them diffuse out into the plasma to prevent the formation of CO2 in the RBCs. 
• In order to maintain the ionic balance of blood plasma, the chloride ions diffuse into the RBCs.
• This phenomenon is called the chloride shift or Hamburger Phenomenon
• The bicarbonate ions in the plasma combine with sodium ions to form sodium bicarbonate. These form an important buffering system.
• The chloride ions combine with potassium ions to form potassium chloride.

3) About 7 percent of CO2 is carried in a dissolved state through plasma:

• Some amount of carbon dioxide forms carbonic acid in the plasma.