Published September 01, 2023 by

Hemoglobin : Definition, Structure, Synthesis, Destruction and Functions


Hemoglobin is a protein that transports oxygen to bodily tissues and organs and carbon dioxide back to the lungs from the lungs in red blood cells. Haemoglobin (Hb) was accidentally discovered in 1840 by Hunefeld in the samples of earthworm blood kept between two glass slides.


The protein hemoglobin is tetrameric in structure. Two polypeptide chain "𝜶" and "𝝱" subunits make up the most prevalent type of adult haemoglobin. Each polypeptide chains are connected by a heme prosthetic group.

• 𝜶 subunit : 𝜶 subunit is made up of polypeptide chain of 141 amino acids.

• 𝝱 subunit : It is made up of a numer of 146 amino corrosive deposits includes in  beta polypeptide chain.

Each polypeptide chain is attached with a prosthetic iron component called the heme group. The centre of the porphyrin ring might include iron.

The quaternary structure has strong connections between the subunits and. Haemoglobin partially separates after a moderate urea treatment, although 𝜶 and  𝝱 dimers remain intact. The subunits are attached by hydrogen bonds, the majority of which are hydrophobic interactions, as well as a few ion pairs or salt bridges.

Haemoglobin typically exists in two states: the R state and the T state. Deoxyhaemoglobin is primarily found in the T state, whereas oxygen has a larger affinity for the R state.

Varients of Hemoglobin 

Genetic variations in specific genes, or globins, which convert the amino acid result in haemoglobin variants. They might have an impact on that particular quality's reliability, design, behaviour, or creation rate. Haemoglobin (Hb) comes in a variety of forms.The most common blood types among them are typically HbA, HbA2, HbF, HbS, HbE, HbC, HbH, and HbM. In healthy individuals, only little quantities of HbA and HbA2 are present. Additionally, some people may have small amounts of HbF.

see molecular formula of hemoglobin 

Ordinary range of Hb in human body

The following are the typical proportions of various molecules in adult haemoglobin:

•HbA: 0.95 to 0.98 (from 95% to 98%).

•HbA2: 0.02 to 0.03 (2% to 3%)

•HbE: 0.008 to 0.02 percent HbF absence

• HbC: Missing 

• HbS: Absence

These HbF particle levels are typical in infants and early children:

• HbF (after six months): 50–80% (0.5–0.8) only 8% • HbF (more than six months): 1% to 2% Hb

Synthesis, Transport, Storage and Destruction of Hb


Haemoglobin is produced by erythrocytes in the bone marrow and circulates with them until they are destroyed. After being divided in the spleen, some of its components, including iron, are then utilised deep inside the marrow.

Haemoglobin is produced biochemically by a complex series of processes, substrates, and enzymes.

The two key phases in the production of haemoglobin are globin synthesis and heme synthesis. Globin chain synthesis occurs by hereditary record and interpretation in the cytoplasm of erythrocytes. Numerous studies have demonstrated that the presence of heme influences globin quality record. The genes for the beta chain are located on chromosome 16, and the genes for the alpha chain are located on chromosome 11. Heme production involves both the cytoplasm and the mitochondria of the erythrocyte. The process starts in the mitochondria since only one of the precursors may be detected there. The third phase, which leads to the formation of heme, is also a mitochondrial process because the concentration of heme influences this reaction. Starting with glycine and succinyl coenzyme A, a protoporphyrin IX ring is created. The protoporphyrin attaches to a Fe2+ ion to produce the final heme molecule.

A series of diseases known as porphyrias cause an accumulation of heme synthesis intermediates in the blood, tissues, and urine, which has clinically important effects. This occurs because of a lack of an enzyme or substrate.


Haemoglobin (Hgb or Hb) is the main oxygen transporter in humans. Only 2% of the total oxygen transported in the blood is free; the majority, around 98%, is bonded to haemoglobin. Red blood cells contain molecules called haemoglobin that take up and transport the oxygen. These oxygen-rich cells go through blood arteries from the lungs to the left side of the heart. After that, the blood is circulated throughout the body. Red platelets are modified to fit the oxygen-carrying vessel.


In this stage of absorption, iron and oxygen combine and are transported into the blood's plasma through binding to transferrin. From there, transferrin and iron are utilised to create haemoglobin, which is then stored in the liver, spleen, and bone marrow for later usage by all body cells.

Hb Excretion and Destruction

Haemoglobin is nearly instantly phagocytized by macrophages in various body areas, including Kupffer cells in the liver, bone marrow, and spleen macrophages, when red blood cells burst and release haemoglobin. A disorder known as autoimmune hemolytic anaemia occurs when the immune system erroneously destroys your own red blood cells because it thinks they are foreign. red cell flaws that are inherited, such as thalassemia, sickle cell anaemia, and a deficiency of G6PD.

Erythrocytes are removed via the reticulo-endothelial system. Globin chains are broken down into amino acids and then reassembled back into globin chains. Iron is once more used by the bone marrow to produce haemoglobin. The breakage of the ring, which results in the formation of the linear tetrapyrrole molecule biliverdin, is the first stage of prototoporphyrin breakdown. Next, biliverdin is changed into bilirubin. Bilirubin is bound to albumin and transferred to the liver where it is conjugated with glucuronic acid. The small intestine and bile are used to get rid of this. The GI tract converts bilirubin into stercobilin, some of which is then reabsorbed into the plasma and excreted by the kidney as urobilinogen in urine. Trace amounts of free haemoglobin may be released into the plasma.

Hb's Functions

1.Transporting oxygen from the lungs or gills to other bodily tissues is hemoglobin's main job. To permit aerobic respiration, which powers the animal's metabolism and makes it simpler to carry carbon dioxide back to the lungs, it releases oxygen there.

2. It buffers the blood's PH and tries to keep up with it.

3. Physical dynamic catabolities' sources.

4. Gives the blood a reddish tint.

5. Genetic resistance to malaria.