Structure, compounds and main types of hemoglobin
The circulatory system performs a transport function in the body of all warm-blooded animals, delivering nutrients and oxygen to the tissues. Transportation of oxygen and carbon dioxide is carried out thanks to the red blood cells, which contain an important substance - hemoglobin. In this article we will consider the types and compounds of hemoglobin.
What is hemoglobin
Hemoglobin is a component of red blood cells belonging to a group of proteins. It consists of 96% of the globin protein substance and 4% of the substance with the 2-valent iron atom - heme. In 1 cell of the erythrocyte it contains about 280 million molecules, which forms the red color of the blood.
The main property of hemoglobin is the ability of the iron to attach and cleave gases, forming the movement of oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs. Thus, its role in the process of gas exchange in the body is irreplaceable.
Structure and types of human hemoglobin
At different stages of the human body, the composition of hemoglobin differs in the structure of polypeptide chains. Depending on which polypeptide chain contains the hemoglobin structure, the hemoglobin species in humans are as follows:
- Adult hemoglobin( HbA) occurs in a dominant amount( about 98-99% of the total in the blood) in adults. HbA consists of 2 and 2 polypeptide chains. Each of the amino acid spirals contains a heme component with an atom responsible for the affinity with the oxygen molecule. HbA has a lower affinity for oxygen than other types of hemoglobin, but at the same time it is more resistant to fluctuations in pH and t.
- Fetal( HbF) is synthesized in the fetus even in the womb starting from 6-7 weeks of pregnancy with subsequent replacement with HbA.From the first month of life, the synthesis of HbF slows down, the total volume of blood increases, and the synthesis of HbA, which by the age of three of the child's life reaches the percentage of the composition of the blood of an adult. Fetal hemoglobin from an adult differs in the composition of globin chains, instead of a chain, a spiral type is present here. HbF, in comparison with HbA, has a lesser degree of resistance to changes in blood pH and fluctuations in body temperature.
- Embryonic( HbE).The primary form of the respiratory protein is produced in the embryo even before the formation of the placenta( already in the first week of pregnancy) and lasts up to 6-7 weeks. The structure is distinguished by the presence of chains and ζ-types.
Pathological types of hemoglobin
In some cases, an abnormal synthesis of hemoglobin cells occurs under the influence of genetic defects. Pathological types of hemoglobin from physiological differ in the composition of polypeptide bonds, or rather, their mutation.
As a result of DNA mutation, the synthesis of erythrocyte components is carried out not with glutamic, but with valine amino acid. This "personnel" replacement leads to the formation of a protein structure of type 2 with a "sticky" patch on the surface, capable of appropriating structures like themselves. Thus, the polymerization of HbS molecules occurs and, as a consequence, the sedimentation of heavy and poorly transported red blood cells in blood vessels. This deviation is called "sickle-cell anemia".
Norms of hemoglobin in humans
The content of protein respiratory structures in the blood in people can differ depending on sex, age category, lifestyle and some other characteristics, such as pregnancy.
Normal values of hemoglobin in the blood, not considered a pathological deviation:
- In men - 130-150 g / l.
- For women - 120-140 g / l.
- Children under the age of 100-140 g / l, and in the first month these values can reach up to 220 g / l due to increased concentrations of fetal hemoglobin. Children from 1 to 6 years old - 110-145 g / l, and from 6 years of age - 115-150 g / l, regardless of the sex of the child.
- In pregnancy, the concentration of HbA is reduced to 110 g / l, which however is not considered an anemia.
- In elderly people, the trend is to decrease by 5 units from the stated rate depending on the sex of the patient.
In terms of age qualification, the composition of blood, which simultaneously contains different types of hemoglobin, differs. For example, in an adult human, the natural ratio is 99% HbA and up to 1% HbF.In children up to a year, the percentage of HbF is significantly higher than in adults, which is explained by the gradual disintegration of the initially available form of fetal hemoglobin.
Since the respiratory red pigment continuously participates in gas-exchange processes in the body, its main property is the ability to form compounds with molecules of different gases. As a result of such reactions, physiological types of hemoglobin are created, which are considered normal.
- Oxyhemoglobin( Hb) is a compound with an oxygen molecule. The process takes place in the respiratory organs, in the alveoli of the lungs. Oxygenated red corpuscles stain blood in a scarlet color, called arterial, and moves from the lungs to the tissues, enriching them with oxygen, necessary for oxidative processes.
- Deoxyhemoglobin( HbH) - reduced hemoglobin is formed at the time when red bodies give off oxygen to tissues, but have not yet had time to take away carbon dioxide from them.
- Carboxyhemoglobin( Hb) is formed by removing carbon dioxide from tissues and bringing it to the lungs, completing the process of human respiration. Carboxyhemoglobin gives venous blood a dark color - burgundy.
Erythrocytes can attach not only gases involved in the respiratory process, but also others, forming pathological hemoglobin species that pose a threat to human health and even life. These compounds have a low degree of decomposition, therefore lead to oxygen starvation of tissues and serious violations of the respiratory process.
- Carbhemoglobin( HbCO) is an extremely dangerous compound in the blood of a person breathing in carbon monoxide. Blocks the ability of red bodies to carry oxygen to tissues. Even an insignificant concentration of carbon monoxide in the air of 0.07% can lead to a lethal outcome.
- Methemoglobin( HbMet) is formed by poisoning with nitrobenzene compounds, examples of which are aliphatic solvents of resins, esters, cellulose, widely applicable in the textile industry. Nitrates, when interacting with hemoglobin, convert the valence iron contained in the heme to a 3 valence iron, which also leads to hypoxia.
Diagnosis of hemoglobin
To determine the concentration of globin respiratory structures in human blood, qualitative and quantitative assays are carried out. Hemoglobin is also examined for the amount of iron ions in it.
The main quantitative method for determining hemoglobin concentration today is colorimetric analysis. It is an investigation of the color saturation of a biological material when a special reagent is added to it.
Qualitative methods include a blood test for the content of HbA and HbF types in it. Also qualitative analysis includes the determination of the amount of blood in the blood of molecules glycosylated hemoglobin( compounds with carbon) - the method is used to diagnose diabetes.
Deviation of hemoglobin concentration from normal
The balance of HbA can vary both below and above normal. In any case, this leads to negative consequences. With a decrease in HbA below the established norm, a pathological syndrome arises, which is called "iron-deficiency anemia".It is expressed by lethargy, loss of strength, inattention. Negatively affects the nervous system, especially dangerous in childhood, because it is often the reason for the lag in the psycho-motor development.
Elevated hemoglobin is not a separate disease, it is rather a syndrome that indicates various pathologies, such as diabetes mellitus, pulmonary insufficiency, heart disease, kidney disease, an overabundance of folic acid or B vitamins, oncology, etc.