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 red blood cells, which include an important substance - hemoglobin. In this article, we will look at the types and compounds of hemoglobin.
What is hemoglobin
Hemoglobin is a component of red blood cells that belongs to the group of proteins. It consists of 96% of the protein substance of globin and 4% of the substance with an atom of 2-valent iron - heme. In 1 cell of an erythrocyte, it contains about 280 million molecules, which forms the red color of blood.
The main property of hemoglobin is the ability of iron to attach and release 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 blood hemoglobin
At different stages of human developmentthe composition of hemoglobin differs in the structure of polypeptide chains. Depending on which polypeptide chains the hemoglobin structure contains, the types of hemoglobin in humans are as follows:
- Adult hemoglobin (HbA) occurs in dominant amounts (about 98-99% of total blood) in adults. HbA consists of 2 and 2 polypeptide chains. Each of the amino acid helices contains a heme component with an atom responsible for the affinity for the oxygen molecule. HbA has less oxygen affinity than other types of hemoglobin, but at the same time it is more resistant to pH and t fluctuations.
- Fetal (HbF) is synthesized in the fetus in the womb starting from 6-7 weeks of pregnancy with its subsequent replacement with HbA. Already from the 1st month of life, the synthesis of HbF slows down, the total blood volume increases, and the synthesis of HbA increases, which by the age of three years of a child's life reaches the percentage of the blood composition of an adult. Fetal hemoglobin differs from an adult in the composition of globin chains; instead of a chain, there is a type of helix here. HbF, compared to HbA, is less resistant 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 under the influencegenetic defects occurs abnormal synthesis of hemoglobin cells. Pathological types of hemoglobin differ from physiological ones in the composition of polypeptide bonds, or rather, in their mutation.
As a result of DNA mutation, the synthesis of erythrocyte components is carried out not with glutamine, but with valine amino acid. This "frame" substitution leads to the formation of a type 2 protein structure with a "sticky" site on the surface that is able to appropriate structures of its own kind. Thus, the polymerization of HbS molecules occurs and, as a result, the sedimentation of heavy and poorly transported erythrocytes in the blood vessels. This deviation is called "sickle anemia".
Norms of hemoglobin content in humans
The content of protein respiratory structures in the blood of people may differ depending on gender, age category, lifestyle and some other features, such as pregnancy.
Normal values of hemoglobin content in the blood, not considered a pathological abnormality:
- Men - 130-150 g/L.
- Women - 120-140 g/l.
- In children up to a year 100-140 g/l, and in the first month these values can reach up to 220 g/l due to the increased concentration of fetal hemoglobin. In children from one year to 6 years - 110-145 g / l, and from 6 years of age - 115-150 g / l, regardless of the sex of the child.
- During pregnancy, there is a decrease in the concentration of HbA to 110 g/l, which, however, is not considered anemia.
- In older people, the trend is considered the normreduction by 5 units from the declared norm, depending on the gender of the patient.
According to the age limit, the composition of blood, which simultaneously contains different types of hemoglobin, also differs. So, for example, in an adult, the natural ratio is 99% HbA and up to 1% HbF. In children under one year old, the percentage of HbF is significantly higher than in adults, which is explained by the gradual breakdown of the initially existing form of fetal hemoglobin.
Physiological Forms
Since the respiratory red pigment is continuously involved in gas exchange processes in the body, its main property is the ability to form compounds with molecules of various 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 occurs in the respiratory organs, in the alveoli of the lungs. Oxygenated red blood cells stain the blood in a scarlet color, which is 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 moment when red cells give oxygen to tissues, but have not yet had time to take carbon dioxide from them.
- Carboxyhemoglobin (Hb) is formed when carbon dioxide is removed from the tissues and carried to the lungs, completing the process of human respiration. Carboxyhemoglobin gives venous blood a dark color - burgundy.
Pathological connections
Erythrocytes can attach not only gases involved in the respiratory process, but also others, forming pathological types of hemoglobin that pose a danger to human he alth and even life. These compounds have a low degree of decomposition, therefore, they 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 who has inhaled carbon monoxide. Blocks the ability of red cells to carry oxygen to tissues. Even a slight concentration of carbon monoxide in the air of 0.07% can be fatal.
- Methemoglobin (HbMet) is formed by poisoning with nitrobenzene compounds, examples of which are aliphatic solvents of resins, ethers, cellulose, widely used in the textile industry. Nitrates, when interacting with hemoglobin, convert the 2-valent iron contained in the heme into 3-valent iron, which also leads to hypoxia.
Hemoglobin diagnostics
To detect the concentration of globin respiratory structures in human blood, qualitative and quantitative types of analyzes are carried out. Hemoglobin is also examined for the amount of iron ions it contains.
The main quantitative method for determining the concentration of hemoglobin today is colorimetric analysis. It is a study of the color saturation of biological material when a special color is added to it.reagent.
Qualitative methods include the study of blood for the content of the ratio of HbA and HbF types in it. Qualitative analysis also includes determining the amount of glycosylated hemoglobin molecules (compounds with carbons) in the blood - the method is used to diagnose diabetes mellitus.
Deviation of hemoglobin concentration from the norm
HbA balance can vary both below and above normal. In any case, this leads to negative consequences. When HbA drops below the established norm, a pathological syndrome occurs, which is called "iron deficiency anemia". It is expressed by lethargy, loss of strength, inattention. It negatively affects the nervous system, it is especially dangerous in childhood, as it often causes a lag in psycho-motor development.
Elevated hemoglobin is not a separate disease, but rather a syndrome that indicates various pathologies, such as diabetes, pulmonary insufficiency, heart disease, kidney disease, an excess of folic acid or B vitamins, oncology, etc.
