Most common Hemoglobin in normal adult is: March 2005
**Core Concept**
In adults, hemoglobin is a tetrameric protein composed of two alpha-globin and two beta-globin chains. Hemoglobin's primary function is to transport oxygen from the lungs to peripheral tissues. The normal adult hemoglobin is a specific type that has a particular structure and function.
**Why the Correct Answer is Right**
The most common hemoglobin in a normal adult is Hemoglobin A (HbA), a tetrameric protein composed of two alpha-globin and two beta-globin chains. HbA is responsible for transporting oxygen from the lungs to the peripheral tissues. It is a product of beta-globin gene expression in erythrocytes. HbA has a specific structure that allows it to bind oxygen reversibly and release it to tissues.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify the type of hemoglobin. Hemoglobin A2 (HbA2) is a minor component of adult hemoglobin, making up about 2-3% of the total hemoglobin.
* **Option B:** This option is incorrect because it does not correspond to any known type of hemoglobin in adults. Hemoglobin F (HbF), also known as fetal hemoglobin, is a major component of fetal hemoglobin but is not the most common hemoglobin in adults.
* **Option C:** This option is incorrect because it is not a specific type of hemoglobin. Hemoglobin variants, such as Hemoglobin S (HbS) and Hemoglobin C (HbC), are abnormal forms of hemoglobin but are not the most common form in normal adults.
**Clinical Pearl / High-Yield Fact**
Remember that Hemoglobin A (HbA) is the most common hemoglobin in normal adults, and its structure and function are critical for maintaining proper oxygen transport. Abnormal hemoglobins, such as HbS, can lead to conditions like sickle cell disease.
**Correct Answer: A. Hemoglobin A (HbA)**