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🔎 Hemoglobin – Definition and Explanations


L’hemoglobin is a protein whose main function is the transport of oxygen in the human body and in other vertebrates (The vertebrates form a subdivision of the animal kingdom. This taxon, which in its…). L’hemoglobin (Hemoglobin is a protein whose main function is the transport of…) is found primarily inside the red blood cells of the blood (Blood is a liquid connective tissue made up of free cell populations, including the…) which gives them their color (Color is the eye’s subjective perception of one or more wave frequencies…) red (The color red responds to different definitions, depending on the chromatic system we are doing…). Hemoglobin is made up of four globins and four heme molecules. The name hemoglobin comes from two words: heme and globin. It is symbolized by “Hb”. A molecule (A molecule is an electrically neutral chemical assembly of at least two atoms, which…) of heme consists of a ion (An ion is an electrically charged chemical species. The term comes from the English,…) iron (Iron is a chemical element, symbol Fe and atomic number 26. It is…) complexed with a porphyrin.


Percentage (A percentage is a way of expressing a proportion or a fraction of a whole. A…) of hemoglobin having fixed dioxygen (Dioxygen is a molecule composed of two oxygen atoms, denoted O2,…)depends on pressure (Pressure is a fundamental physical notion. You can think of it as a reported force…) partial in oxygen.

In terrestrial vertebrates, the hemoglobin of the blood binds the dioxygen of theair (Air is the mixture of gases that make up the Earth’s atmosphere. It is odorless and…) lungs. Thanks to the blood circulation (Blood circulation is a type of closed-circuit circulatory system that ensures…)the oxygenated hemoglobin will be transported to thetogether (In set theory, a set intuitively designates a collection…) other organs, to subsequently release the dioxygen which will be consumed by the cells that have it need (Needs are at the level of the interaction between the individual and the environment. It is…). Hemoglobin allows the blood to hold more oxygen than it could by simple dissolution.

Oxygen binding


In the tetrameric form of normal hemoglobin, binding with oxygen, or oxyhemoglobin formation, is a cooperative, or allosteric, process where hemoglobin’s binding affinity for oxygen is affected by saturation. in oxygen of the molecule. This has the consequence that the curve (In geometry, the word curve, or curved line designates certain subsets of…) oxygen affinity for hemoglobin has the shape of a sigmoid (S-shaped curve), unlike a non-cooperative (Mickaelian) process where it has a hyperbolic shape.

The affinity of hemoglobin for oxygen decreases in the presence of carbon dioxide (Carbon dioxide, commonly known as carbon dioxide or carbon dioxide, is a…)at low pH and when the temperature (Temperature is a physical quantity measured using a thermometer and…) increase. These chemical properties are essential to life since they allow a better release of dioxygen in active tissues (ex: the muscular (Muscles are a contractile form of animal tissue. They are one of four types…) in exercise, by the production of metabolites develops a pH acid (An acid is a chemical compound generally defined by its reactions…), its temperature increases affirming the dissociation of dioxygen from heme). The dioxide of carbon (Carbon is a chemical element of the family of crystallogens, symbol C,…) reacts with thewater (Water is a ubiquitous chemical compound on Earth, essential for all…) to form bicarbonate via the reaction:

CO2 +H2O ↔ HCO3 +H+

By this reaction we see that blood with a high level of carbon dioxide also has a lower pH. Hemoglobin can bind protons and carbon dioxide which induced (The armature is a generally electromagnetic device used in electrical engineering responsible for…) a change of conformation (In chemistry, the conformation of a molecule is the spatial arrangement of the atoms that compose it….) in the protein (A protein is a biological macromolecule composed of one or more…) which facilitates the release of oxygen. the proton (The proton is a subatomic particle carrying an elementary electric charge…) can bind at different places along the protein, whereas carbon dioxide binds on the alpha-amino group in forming (In intonation, fundamental frequency changes are perceived as variations of…) a carbamate. This control (The word control can have several meanings. It can be used as a synonym of examination, of…) is called the Bohr effect. Similarly, when the level of carbon dioxide in the blood drops (for example near the lungs), the carbon dioxide is released, increasing the protein’s affinity for oxygen. This control of oxygen’s affinity for binding to hemoglobin and releasing carbon dioxide is known as the Haldane effect.

Oxygen binding is also affected by molecules such as 2,3-diphosphoglycerate, which decreases the affinity of hemoglobin for oxygen. In people acclimatized to high altitudes, the concentration of 2,3-diphosphoglycerate in the blood is greater, which allows hemoglobin to deliver greater amounts of oxygen to tissues in low oxygen atmospheres.

Hemoglobin poisons

On the other hand, with the carbon monoxide (Carbon monoxide is one of the oxides of carbon. Its formula is written CO and its formula…) CO, hemoglobin forms a stable compound, carboxyhemoglobin; furthermore, the affinity of hemoglobin for carbon monoxide is greater than that for oxygen, which means that CO effectively competes with oxygen during oxidation pulmonary (The lungworts are plants of the Boraginaceae family belonging to the genus…). CO is therefore an antagonist of O2which can thus cause tissue hypoxia: its inhalation at high doses causes discomfort, headaches (headaches), then asthenia (intense weakness) and finally the dead (Death is the final state of a biological organism that ceases to live (even if…) by asphyxia (Asphyxia is a medical term meaning the more or less long stoppage of circulation…). Severe CO poisoning is treated by prolonged immersion in a hyperbaric chamber, thus reducing the half-life of carboxyhemoglobin.

In addition, oxidizing agents such as nitrates in water or vegetables can oxidize ferrous iron (Fe2+) of ferric iron heme (Fe3+), making it unable to bind oxygen. Hemoglobin is then called methemoglobin. The treatment consists of the administration of blue (Blue (from Old High German “blao” = brilliant) is one of the three colours…) of methylene.

Finally, the ion cyanide (Cyanides are the compounds of the anion CN-, formed from a carbon atom bonded by…) NC is also an inhibitor of hemoglobin oxidation, as is sulfide (In chemistry, a sulfide is a chemical compound or the combination of sulfur with a degree…) ofhydrogen (Hydrogen is a chemical element with symbol H and atomic number 1.) H2S.