- A Bound to plasma albumin proteins according to standard texts
- B Dissolved directly in blood plasma in most observed cases
- C As bicarbonate ions in plasma under typical physiological conditions
- D Bound to haemoglobin within red blood cells
Correct answer: D. Bound to haemoglobin within red blood cells
Explanation: About 97% of oxygen in blood is transported bound to haemoglobin as oxyhaemoglobin within red blood cells; only a small fraction dissolves directly in plasma.
Concept context
The mechanics of breathing, lung volumes, gas transport in blood, the Bohr effect, and respiratory regulation.