Hemoglobin is a coordinate compound in which the central metal atom is?

KPSC Staff Nurse - 2015

Biochemistry & Nutrition

Easy

Appeared in: KPSC Staff Nurse - 2015

Explanation

Hemoglobin is a protein responsible for oxygen transport in the blood.
Each hemoglobin molecule contains four heme groups, and at the center of each heme group is a single atom of iron (Fe).
The iron atom is in the ferrous (Fe²⁺) state, which allows it to bind reversibly with one molecule of oxygen.
This iron-oxygen bond is what enables hemoglobin to pick up oxygen in the lungs and deliver it to the body's tissues.

Option A: Sodium is an essential electrolyte responsible for fluid balance and nerve function, but it is not a structural component of the hemoglobin molecule.
Option B: Magnesium is the central metal atom in chlorophyll, the pigment that enables photosynthesis in plants. It is not part of hemoglobin.
Option C: Manganese is an important trace element that acts as a cofactor for various enzymes (e.g., arginase, isocitrate dehydrogenase), but it is not the central metal in hemoglobin.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Structure and Composition of Hemoglobin as background academic context rather than a clinical decision trigger.
Understanding that iron is central to hemoglobin is fundamental for comprehending conditions like iron-deficiency anemia, the most common type of anemia worldwide. A nurse must be able to recognize its signs (pallor, fatigue) and educate patients on iron-rich diets and supplements.
Knowledge of hemoglobin's structure is also key to understanding toxic exposures. For example, carbon monoxide (CO) has a much higher affinity for the heme iron than oxygen, leading to CO poisoning and severe hypoxia.
What if? If a patient presents with cyanosis (bluish skin) that doesn't improve with oxygen therapy, the nurse should consider methemoglobinemia. In this condition, the heme iron is oxidized to Fe³⁺, which cannot bind oxygen. This is a medical emergency requiring specific interventions like methylene blue administration.

How to Approach the Question

First, identify the key terms in the question: 'Hemoglobin' and 'central metal atom'.
This is a factual recall question that tests your knowledge of the basic biochemical structure of a vital protein.
Access your memory about the composition of blood and red blood cells. Recall that hemoglobin is the primary protein involved in oxygen transport.
Systematically evaluate each option. Think about the biological role of each metal listed.
Eliminate options known for other primary functions (e.g., Sodium as an electrolyte, Magnesium in chlorophyll).
Select the option that is famously associated with hemoglobin and oxygen transport, which is Iron.

Concept Tested & Keywords

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E6 Harper's Illustrated Biochemistry2023 (pp 26-793 of 813) pp. 34-36, 84-86

E6 Physiology Guyton 4SAE Part 1 p. 183-184