A huge role for the normal functioning of the human body is played by acid-base balance. The blood circulating in the body is a mixture of living cells that are in a liquid environment. The first line of protection that controls the pH level in the blood is the buffer system . This is a physiological mechanism that ensures the preservation of acid-base balance parameters, preventing pH changes. What is it and what are the varieties, we learn below.
Description
The buffer system is a unique mechanism. There are several of them in the human body, and they all consist of plasma and blood cells. The buffers are bases (proteins and inorganic compounds) that bind or give off H + and OH-, destroying the pH shift for thirty seconds. The ability of a buffer to maintain an acid-base balance depends on the number of elements of which it is composed.
Types of Blood Buffers
Blood, which is constantly moving, is a living cell that exists in a liquid medium. The pH is normally 7.37-7.44. A bunch of ions occurs in a specific buffer, the classification of buffer systems is given below. It itself consists of plasma and blood cells and can be phosphate, protein, bicarbonate or hemoglobin. All these systems have a fairly simple mechanism of action. Their activity is aimed at regulating the level of ions in the blood.
Hemoglobin Buffer Features
The hemoglobin buffer system is the most powerful of all, it is an alkali in the capillaries of tissues and acid in an internal organ such as the lungs. It accounts for about seventy-five percent of the total buffer capacity. This mechanism is involved in many processes that occur in human blood, and has a globin in its composition. When the hemoglobin buffer passes into another form (oxyhemoglobin), a change in this form is observed, and the acid properties of the active substance also change.
The quality of reduced hemoglobin is lower than that of carbonic acid, but it becomes much better when it is oxidized. When pH is acquired, hemoglobin combines hydrogen ions, it turns out that it is already reduced. When carbon dioxide is purged in the lungs, the pH is alkaline. At this time, hemoglobin, which is oxidized, acts as a proton donor, with the help of which the balance of the acid-base balance occurs. So, the buffer, which consists of oxyhemoglobin and its potassium salt, promotes the release of carbon dioxide from the body.
This buffer system plays an important role in the respiratory process, as it performs a transport function to transfer oxygen to tissues and internal organs and remove carbon dioxide from them. The acid-base balance inside the red blood cells is kept at a constant level, therefore, in the blood as well.
Thus, when the blood is saturated with oxygen, hemoglobin turns into a strong acid, and when it gives oxygen, it turns into a rather weak organic acid. The systems of oxyhemoglobin and hemoglobin are interconverting, they exist as a whole.
Features of bicarbonate buffer
The bicarbonate buffer system is also powerful, but also the most manageable in the body. It accounts for about ten percent of the total buffer capacity. It has universal properties that provide its two-way effectiveness. This buffer contains a conjugated acid-base pair, which consists of molecules such as carbonic acid ( proton source ) and anion bicarbonate (proton acceptor).
So, the bicarbonate buffer system promotes a systematic process, where powerful acid enters the bloodstream. This mechanism binds acid with bicarbonate anions, forming carbonic acid and its salt. When alkali enters the blood, the buffer binds to carbonic acid, forming a bicarbonate salt. Since sodium bicarbonate in human blood is greater than carbonic acid, this buffer capacity will have high acidity. In other words, a hydrocarbonate buffer system (bicarbonate) Very well compensates for substances that increase blood acidity. Lactic acid also belongs to them, the concentration of which increases with intense physical exertion, and this buffer reacts very quickly to changes in the acid-base balance in the blood.
Phosphate Buffer Features
The human phosphate buffer system occupies nearly two percent of the entire buffer capacity, which is associated with the content of phosphates in the blood. This mechanism maintains the pH in the urine and fluid that is inside the cells. The buffer consists of inorganic phosphates: monobasic (acts as an acid) and dibasic (acts as an alkali). At a normal pH, the ratio of acid to base is 1: 4. With an increase in the number of hydrogen ions, the phosphate buffer system binds to them, forming acid. This mechanism is more acidic than alkaline, so it perfectly neutralizes acid metabolites entering the bloodstream, for example, lactic acid.
Protein Buffer Features
Protein buffer does not play such a special role in stabilizing the acid-base balance, in comparison with other systems. It accounts for about seven percent of the total buffer capacity. Proteins are made up of molecules that combine into acid-base compounds. In an acidic environment, they act as alkalis that bind acids; in an alkaline environment, everything happens the other way around.
This leads to the formation of a protein buffer system , which is quite effective at a pH value from 7.2 to 7.4. A large proportion of proteins is represented by albumin and globulin. Since the protein charge is zero, then at a normal pH, it is in the form of alkali and salt. This buffer capacity depends on the amount of proteins, their structure and free protons. This buffer can neutralize both acidic and alkaline products. But its capacity is more acidic than alkaline.
Erythrocyte features
Red blood cells normally have a constant pH of 7.25. Here bicarbonate and phosphate buffers act. But in power they differ from those in the blood. In erythrocytes, protein buffer plays a special role in providing organs and tissues with oxygen, as well as removing carbon dioxide from them. In addition, it maintains a constant value within the erythrocytes pH. The protein buffer in red blood cells is closely related to the hydrocarbonate system, since the ratio of acid to salt is lower than in the blood.
Buffer system example
Solutions of strong acids and alkalis, which have weak reactions, have a variable pH. But the mixture of acetic acid with its salt retains a stable value. Even if you add acid or alkali to them, the acid-base balance will not change. An example is the acetate buffer, which consists of the acid CH 3 COOH and its salt CH 3 COO. If you add strong acid, then the base of the salt will bind H + ions and turn into acetic acid. A decrease in salt anion levels is balanced by an increase in acid molecules. As a result of this, there is a slight change in the ratio of acid to its salt, so the pH changes completely unnoticed.
The mechanism of action of buffer systems
When acidic or alkaline products enter the bloodstream, the buffer provides a constant pH value until the products that are released are removed or used in metabolic processes. Four buffers are represented in human blood, each of which consists of two parts: acid and its salt, as well as strong alkali.
The effect of the buffer is determined by the fact that it binds and neutralizes the ions that enter its corresponding composition. Since in nature the body is most likely to encounter under-oxidized metabolic products, the buffer has more acidic properties than anti-alkaline ones.
Each buffer system has its own principle of operation. With a decrease in pH below 7.0, their vigorous activity begins. They begin to bind excess free hydrogen ions, forming complexes that transport oxygen. He, in turn, moves to the digestive system, lungs, skin, kidneys, and so on. Such transportation of acidic and alkaline products contributes to their unloading and removal.
In the human body, only four buffer systems play important roles in maintaining the acid-base balance, but there are other buffers, for example, the acetate buffer system, which has a weak acid (donor) and its salt (acceptor). The ability of these mechanisms to withstand changes in pH when acid or salt enters the bloodstream is limited. They maintain acid-base balance only when a strong acid or alkali comes in a certain amount. If it is exceeded, the pH will change dramatically, the buffer system will cease to function.
Buffer Efficiency
Blood and red blood cell buffers have different efficiencies. In the latter, it is higher, since there is a hemoglobin buffer. The decrease in the number of ions occurs in the direction from the cell to the intercellular medium, and then to the blood. This suggests that the largest buffer capacity in the blood, and the intracellular environment has a smaller one.
With metabolism, acids appear in the cells that pass into the intercellular fluid. This happens the easier as they appear in the cells more, since an excess of hydrogen ions increases the permeability of the cell membrane. We already know the classification of buffer systems . In erythrocytes, they have more effective properties, since collagen fibers play a role here, which react by swelling to the accumulation of acid, they absorb it and release red blood cells from hydrogen ions. This ability is determined by the absorption property.
The interaction of buffers in the body
All the mechanisms that are in the body are interconnected. Blood buffers consist of several systems whose contribution to maintaining the acid-base balance is different. When blood enters the lungs, it receives oxygen by binding it to hemoglobin in red blood cells, forming oxyhemoglobin (acid), which maintains the pH level. With the assistance of carbonic anhydrase, a parallel purification of the blood of lungs from carbon dioxide occurs, which in erythrocytes is represented as a weak dibasic carbonic acid and carbaminogemoglobin, and in the blood - carbon dioxide and water.
With a decrease in the amount of weak dibasic carbonic acid in red blood cells, it penetrates from the blood into the red blood cell, and the blood is cleansed of carbon dioxide. Thus, weak dibasic carbonic acid constantly passes from the cells into the blood, and inactive chloride anions come from the blood to red blood cells to maintain neutrality. As a result, the medium in red blood cells is more acidic than in plasma. All buffer systems are justified by the proton donor – acceptor ratio (4:20), which is associated with the peculiarities of the human body metabolism, which forms a greater number of acidic products than alkaline ones. Very important here is the indicator of acid buffer capacities.
Tissue metabolic processes
The acid-base balance is maintained by buffers and metabolic transformations in body tissues. This is helped by biochemical and physicochemical processes. They contribute to the loss of acid-base properties of metabolic products, their binding, the formation of new compounds that are rapidly excreted from the body. For example, a large amount of lactic acid is excreted into glycogen, organic acids are neutralized by sodium salts. Strong acids and alkalis dissolve in lipids, and organic acids undergo oxidation to form carbonic acid.
Thus, the buffer system is the first assistant in normalizing the acid-base balance in the human body. PH stability is necessary for the normal functioning of biological molecules and structures, organs and tissues. Under normal conditions, buffer processes maintain a balance between the appearance and removal of hydrogen ions and carbon dioxide, which helps to ensure a constant pH level in the blood.
If there is a malfunction in the functioning of the buffer systems, then a person has pathologies such as alkalosis or acidosis. All buffer systems are interconnected and aimed at maintaining a stable acid-base balance. A large number of acidic products are constantly formed in the human body, which is equivalent to thirty liters of strong acid.
The constancy of reactions within the body is ensured by powerful buffers: phosphate, protein, hemoglobin and bicarbonate. There are other buffer systems, but these are the main and most necessary for a living organism. Without their help, a person will begin to develop various pathologies that can lead to a coma or death.