Question

During single circulation of the blood from lungs to the tissues and back through the circulatory system, the percentage of haemoglobin giving up its oxygen to the tissue is:

• A. 50%
• B. 25%
• C. 75%
• D. 80%

Answer 1

The correct option is B 25%

Blood contains specialized cells known as erythrocytes. These are flattened discs, which gives them a greater surface area to exchange oxygen and carbon dioxide in the lungs and with body cells. It carries oxygen efficiently due to the presence of the protein haemoglobin which has an iron atom at its centre. When bound to oxygen, this haem group is known as oxyhaemoglobin. One molecule of haemoglobin can bind four oxygen molecules in a reversible way. So, the correct answer is option B.