Question

Carbon dioxide is primarily carried throughout the body...

Select one:

a. By dissolving into plasma

b. By binding to hemoglobin

c. As bicarbonate

d. By binding to myoglobin

e. By dissolving into red blood cells

Answer 1

Carbon dioxide is produced by cell metabolism in the mitochondria in the cells of the tissues in the body.

the formed carbon dioxide is transported in the body in three ways:

(i) dissolved in solution;

(ii) buffered with water as carbonic acid;

(iii) bound to proteins, particularly hemoglobin.

majorly up to 75% of carbon dioxide is transport in the red blood cell and 25% in the plasma.

The small amount in plasma is due to lack of carbonic anhydrase in plasma so the solubility in water is slow hence the option a: By dissolving into plasma is false.

carbon dioxide can bind to plasma proteins or can enter red blood cells and bind to hemoglobin but in this form, only 10 percent of the carbon dioxide is transported. Hence the option b:  By binding to hemoglobin is false.

the majority of carbon dioxide nearly 85 percent is carried as bicarbonate. In this, the carbon dioxide diffuses into the red blood cells and gets converted into carbonic acid (H2CO3) by the action of an enzyme carbonic anhydrase. Since, the Carbonic acid is unstable, it immediately dissociates into bicarbonate ions (HCO−3)(HCO3−) and hydrogen (H+) ions. Since carbon dioxide is quickly converted into bicarbonate ions, this reaction allows for the continued uptake of carbon dioxide into the blood down its concentration gradient. hence the option c: As bicarbonate is true

coming to the option d: By binding to myoglobin; myoglobin is the protein present in the muscle cells that carries oxygen inside the muscle. hence this option is not true.

the options e. By dissolving into red blood cells is also not true because when the carbon dioxide enters into RBC it gets converted into bicarbonate.