Normal adult haemoglobin contains? & x20;

Two alpha chains and two beta chains

One alpha chain and one beta chain

One alpha chain and two beta chains

One beta chain and two alpha chains

SJH Nursing Officer - 2019

Biochemistry & Nutrition

Easy

Normal adult haemoglobin contains?

Appeared in: SJH Nursing Officer - 2019

Normal adult hemoglobin (HbA) is the most common type of hemoglobin in adults, making up over 95% of the total.
HbA is a tetrameric protein, meaning it is composed of four polypeptide chains.
The specific structure of HbA consists of two alpha (α) globin chains and two beta (β) globin chains.
This composition is denoted as α₂β₂, which is essential for its function of reversibly binding and transporting oxygen.

Option A: This describes a dimer (two chains), not the correct tetramer (four chains) structure of hemoglobin.
Option B: This describes an incorrect ratio of chains (one alpha, two beta). Hemoglobin requires a balanced 2:2 ratio of alpha-like and beta-like chains.
Option C: This describes an incorrect ratio of chains (two alpha, one beta). A complete hemoglobin tetramer requires two beta-like chains to pair with the two alpha chains.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Composition of normal adult hemoglobin (HbA) as background academic context rather than a clinical decision trigger.
Understanding the normal structure of hemoglobin is fundamental for diagnosing hemoglobinopathies. For example, in sickle cell disease, a mutation affects the beta-globin chain, while in thalassemias, there is a reduced production of either alpha or beta chains.
Nurses monitor hemoglobin levels as a key indicator of a patient's oxygen-carrying capacity. Abnormal levels can signify anemia, bleeding, or other systemic diseases.
What if? If a patient's lab results showed a significantly elevated level of Hemoglobin F (HbF) in adulthood, a nurse should suspect an underlying condition like β-thalassemia or hereditary persistence of fetal hemoglobin, as HbF production is normally suppressed after infancy.

How to Approach the Question

Identify the core of the question: it asks for the composition of 'normal adult haemoglobin'.
Recall the basic structure of hemoglobin. It's a protein made of four subunits (a tetramer).
Remember the different types of globin chains: alpha (α), beta (β), gamma (γ), and delta (δ).
Associate 'adult' hemoglobin (HbA) with the most common combination, which is α₂β₂.
Evaluate the options based on this knowledge. Option D correctly identifies two alpha and two beta chains.

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Practise the full SJH Nursing Officer - 2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.