Each hemoglobin contains
**Core Concept**
The question is testing knowledge of the structure and composition of **hemoglobin**, a crucial protein in red blood cells responsible for oxygen transport. Hemoglobin is composed of **heme** and **globin** parts. Understanding the basic structure of hemoglobin is fundamental in physiology and biochemistry.
**Why the Correct Answer is Right**
Each hemoglobin molecule contains four **heme groups** and four **globin chains**. The heme groups are the sites where oxygen binds, and the globin chains provide the structure that holds these heme groups in place. This composition allows hemoglobin to efficiently transport oxygen from the lungs to the body's tissues.
**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because it does not accurately reflect the composition of hemoglobin.
**Option B:** Similarly, this option does not correctly describe the components of hemoglobin.
**Option C:** This choice is also incorrect as it misrepresents the structure of hemoglobin.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that normal adult hemoglobin (HbA) is composed of two alpha and two beta globin chains, and each chain is associated with a heme group. This knowledge is essential for understanding various hemoglobinopathies.
**Correct Answer:** D. 4 heme groups