The Amount of 02 normally carried by 100 ml of pure blood, is A. 40 ml B. 10 ml C. 20 ml D. 30 ml

The correct answer is C. 20 ml.
The amount of oxygen (O₂) carried by 100 ml of pure blood is approximately 20 ml under normal physiological conditions. This oxygen is primarily transported in the blood in two ways:
1. Bound to Hemoglobin:
• Each molecule of hemoglobin can bind up to four molecules of oxygen.
• On average, 1 gram of hemoglobin binds 1.34 ml of oxygen.
• Normal blood contains about 15 grams of hemoglobin per 100 ml.
• Therefore, hemoglobin carries 15 × 1.34 = ~20 ml of oxygen per 100 ml of blood when fully saturated.
2. Dissolved in Plasma:
• A very small amount of oxygen is dissolved directly in the plasma.
• This contributes only about 0.3 ml of oxygen per 100 ml of blood at normal atmospheric pressure.
Total Oxygen Carried:
• The majority of oxygen (around 98%) is carried bound to hemoglobin, with a small fraction dissolved in the plasma.
• Thus, 20 ml of oxygen per 100 ml of blood is the standard amount carried under normal physiological conditions.
Why Other Options Are Incorrect:
• A. 40 ml: This is too high; normal blood cannot carry this much oxygen due to the saturation limits of hemoglobin.
• B. 10 ml: This is too low for normal blood oxygen levels.
• D. 30 ml: This is higher than the oxygen-carrying capacity of normal hemoglobin under typical conditions.
The amount of oxygen normally carried by 100 ml of pure blood is approximately 20 ml, making C. 20 ml the correct answer.