The amount of hemoglobin in blood is one of the important health markers. Following statements are made regarding hemoglobin degradation when older red blood cells (RBCs) are destroyed by tissue macrophages:

A. The globin protein of the hemoglobin is split off and is converted first to bilirubin by the action of heme oxygenase.
B. The globin protein of the hemoglobin is split off and is converted first to biliverdin by the action of heme oxygenase.
C. Carbon monoxide (CO) is formed in the process.
D. Nitric oxide (NO) is formed in the process.

Which one of the following represents the correct combination of statements?

Correct option is B

Explanation-

Statement A - The globin protein of the hemoglobin is split off and heme is converted first to bilirubin by the action of heme oxygenase  - INCORRECT
Heme oxygenase first converts heme to biliverdin, not bilirubin. Biliverdin is later converted to bilirubin by biliverdin reductase.
​Statement B -  The globin protein of the hemoglobin is split off and heme is converted first to biliverdin by the action of heme oxygenase - CORRECT
This is the correct sequence:
      (i)  Hemoglobin → globin + heme
      (ii) Heme → biliverdin (by heme oxygenase) + Fe²⁺ + CO
      (iii) Biliverdin → bilirubin (by biliverdin reductase)
Statement C - Carbon monoxide (CO) is formed in the process  - CORRECT
The heme oxygenase reaction releases CO as a byproduct. This is one of the few endogenous sources of CO in humans.
Statement D -  Nitric oxide (NO) is formed in the process - INCORRECT
NO is not produced during heme degradation. NO is synthesized separately by nitric oxide synthase (NOS) from arginine.

Final Answer:
Correct statements: B and C (Option b)