Question

Carbon dioxide is transported in blood mainly as:

• A. Carbaminohaemoglobin
• B. Dissolved \(CO_2\)
• C. Bicarbonate ions
• D. Carbonic acid

Hint:

The enzyme Carbonic Anhydrase is essential for the rapid conversion of \(CO_2\) into bicarbonate. It is found in extremely high concentrations within Red Blood Cells.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Carbon dioxide (\(CO_2\)) is a waste product of cellular respiration. It is transported from the tissues to the lungs through the bloodstream in three different chemical forms.

Step 2: Detailed Explanation:
The distribution of \(CO_2\) transport is as follows:
1. As Bicarbonate ions (\(HCO_3^-\)): This is the major form, accounting for about \(70\%\) of \(CO_2\) transport. Within the RBCs, \(CO_2\) reacts with water to form carbonic acid (\(H_2CO_3\)) via the enzyme carbonic anhydrase. This acid then dissociates into bicarbonate and hydrogen ions.
2. As Carbaminohaemoglobin: About \(20-25\%\) of \(CO_2\) binds directly to the amino groups of the haemoglobin protein.
3. In Dissolved Form: About \(7\%\) of \(CO_2\) is transported simply dissolved in the plasma.

Step 3: Final Answer:
Carbon dioxide is transported mainly in the form of bicarbonate ions.