Question

Shortly explain how oxygen and carbon dioxide is transported to all parts of our body. Mention the significance of hemoglobin.

Answer 1

Oxygen transport: Oxygen is carried by the blood in two forms.
1. Solution: Being slightly soluble in water, a small amount of oxygen (about 3%) travels as its solution in plasma.
2. Oxyhaemoglobin: Bulk of oxygen (about 97%) diffuses from the plasma into the red blood corpuscles. Here it loosely joins with the haemoglobin to form bright red oxyhaemoglobin. The process is called oxygenation. Single haemoglobin molecule can combine with four oxygen molecules. Thus, an oxyhaemoglobin molecule may carry one to four oxygen molecules, depending on its degree of saturation with oxygen.
Carbon dioxide transport: Carbon dioxide is carried by the blood in three forms.
1. Physical solution: A very small amount of carbon dioxide (about 7%) dissolves in the plasma and is carried as physical solution.
2. Bicarbonate ions: About 70% of carbon dioxide released by respiring tissue cells diffuse into the plasma and then into red blood corpuscles. Here, CO₂ combines with water to form carbonic acid. The reaction is catalyzed by a zinc containing enzyme carbonic anhydrase. Carbonic acid dissociates into bicarbonate ions and hydrogen ions. Hydrogen ions are picked by proteins and bicarbonate ions are joined by bases (Na⁺, K⁺) to maintain pH of the blood.
3. Carbaminohaemoglobin: About 23% of CO₂ entering the RBCs loosely combines with the amino group of the reduced haemoglobin to form carbaminohaemoglobin. The reaction releases oxygen from oxyhaemoglobin.
Significance of haemoglobin
Haemoglobin present in red blood cells combines loosely and reversibly with oxygen present in the lungs and then release this oxygen in the tissue capillaries.