Question

Oxyhaemoglobin is converted into haemoglobin during the internal respiration because

• A. An enzyme splits oxyhaemoglobin
• B. Oxygen tension in tissues is less than capillary blood reaching tissues
• C. CO${}_2$ tension is low in blood that reaches tissues
• D. Oxyhaemoglobin is unstable

Answer 1

Answer: (B)

Oxygen tension in tissues is less than capillary blood reaching tissues

A small amount of oxygen does dissolve in the blood and is transported in the bloodstream, but it is only about 1.5% of the total amount. The majority of oxygen molecules are carried from the lungs to the body’s tissues by a specialized transport system, which relies on the erythrocyte—the red blood cell. Heme is the portion of hemoglobin that contains iron, and it is heme that binds oxygen. One hemoglobin molecule contains iron-containing heme molecules, and because of this, each hemoglobin molecule is capable of carrying up to four molecules of oxygen. As oxygen diffuses across the respiratory membrane from the alveolus to the capillary, it also diffuses into the red blood cell and is bound by hemoglobin. The following reversible chemical reaction describes the production of the final product, oxyhemoglobin (Hb–O2), which is formed when oxygen binds to hemoglobin.

So, the correct option is 'Oxygen tension in tissues is less than capillary blood reaching tissues'.