Hematology — Which mineral is required as an essential component of blood hemoglobin for oxygen transport?

Introduction / Context:
Hemoglobin in red blood cells transports oxygen from lungs to tissues. Its oxygen-binding capacity depends on a specific metal atom embedded in the heme prosthetic group. This question asks you to identify that mineral component essential for functional hemoglobin.

Given Data / Assumptions:

• Heme consists of protoporphyrin IX chelating a divalent metal ion.
• Reversible oxygen binding requires correct oxidation state and coordination.
• Deficiency of the metal leads to impaired erythropoiesis and anemia.

Concept / Approach:
Iron (Fe2+) sits at the center of heme groups within hemoglobin, directly coordinating oxygen. Iron deficiency compromises hemoglobin synthesis, resulting in microcytic, hypochromic anemia with fatigue, pallor, and reduced exercise tolerance. Adequate dietary iron and proper absorption/regulation (hepcidin pathway) are critical to maintain erythron iron supply.

Step-by-Step Solution:

Verification / Alternative check:
Laboratory indices (low ferritin, low transferrin saturation, low mean corpuscular volume) confirm iron-deficiency anemia; iron repletion restores hemoglobin and oxygen-carrying capacity.

Why Other Options Are Wrong:

• Magnesium/Calcium: important in many processes, but not the heme metal.
• Copper: assists iron mobilization (ceruloplasmin) but is not part of hemoglobin’s heme.
• Cobalt: central to vitamin B12, not to hemoglobin heme.

Common Pitfalls:
Confusing cofactors aiding iron metabolism (copper, vitamin C) with the heme iron itself. Only iron binds oxygen within hemoglobin.

Final Answer:
Iron.