Question

Which of the following statements is/are true about the gas content of human blood?

A. Most of the oxygen contained in human blood is bound to hemoglobin rather than in solution and this bound hemoglobin does not contribute directly to the partial pressure of oxygen in the blood

B. Most of the carbon dioxide contained in human blood is in solution in the plasma, with only a small fraction present as bicarbonate

C. The percent saturation of hemoglobin in human blood in alveolar capillaries would be expected to double if the partial pressure of oxygen in the alveolar spaces is doubled from 0.13 atm to 0.26 atm

D. Two of the three answers given are correct

Answer 1

Answer: A. Most of the oxygen contained in human blood is bound to hemoglobin rather than in solution and this bound hemoglobin does not contribute directly to the partial pressure of oxygen in the blood

Explanation:

Option B is incorrect because around 60% of the CO2 is transported as bicarbonate. while 30% is bound to haemoglobin and a mere 10% is dissolved in blood plasma

Option C is incorrect because Around 98.5% of oxygen is transported with the help of Haemoglogin and the remaining small fraction is carried as dissolved oxygen in blood.

At 0.13atm (or 98 mm Hg), the curve of % saturation of haemoglobin vs. partial pressure of oxygen has reached saturation. Hence, even though pressure is doubled, saturation will not change.

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