Acid-base balance plays a huge role in the normal functioning of the human body. The blood circulating in the body is a mixture of living cells that are in a liquid habitat. The first security feature that controls the pH level in the blood is the buffer system. This is a physiological mechanism that ensures that the parameters of the acid-base balance are maintained by preventing pH drops. What it is and what varieties it has, we will find out 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. Buffers are bases (proteins and inorganic compounds) that bind or donate H+ and OH-, destroying the pH shift within 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 that is constantly moving is living cells,that exist in a liquid medium. Normal pH is 7, 37-7, 44. The binding of ions occurs with a certain 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.
Features of hemoglobin buffer
The hemoglobin buffer system is the most powerful of all, it is an alkali in the capillaries of tissues and an acid in such an internal organ 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 globin in its composition. When the hemoglobin buffer changes to another form (oxyhemoglobin), this form changes, and the acidic properties of the active substance also change.
The quality of reduced hemoglobin is less than that of carbonic acid, but becomes much better when it is oxidized. When the acidity of pH is acquired, hemoglobin combines hydrogen ions, it turns out that it is already reduced. When carbon dioxide is cleared from the lungs, the pH becomes alkaline. At this time, hemoglobin, which has been oxidized, acts as a proton donor, with the help of which the acid-base balance is balanced. So, the buffer, which consists of oxyhemoglobin and its potassium s alt, promotes the release of carbon dioxide from the body.
This buffer system performsan important role in the respiratory process, as it performs the transport function of transferring oxygen to the tissues and internal organs and removing carbon dioxide from them. The acid-base balance inside the erythrocytes is maintained 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 up oxygen, it turns into a fairly weak organic acid. The systems of oxyhemoglobin and hemoglobin are interconvertible, they exist as one.
Features of bicarbonate buffer
The bicarbonate buffer system is also powerful, but also the most controlled in the body. It accounts for about ten percent of the total buffer capacity. It has versatile properties that ensure 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).
Thus, the bicarbonate buffer system promotes a systematic process where a powerful acid enters the bloodstream. This mechanism binds the acid to the bicarbonate anions, forming carbonic acid and its s alt. When alkali enters the blood, the buffer binds to carbonic acid, forming a bicarbonate s alt. Since there is more sodium bicarbonate in human blood than carbonic acid, this buffer capacity will have a high acidity. In other words, hydrocarbon bufferthe system (bicarbonate) is very good at compensating for substances that increase the acidity of the blood. These include lactic acid, 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.
Features of phosphate buffer
The human phosphate buffer system occupies close to two percent of the total buffer capacity, which is related to the content of phosphates in the blood. This mechanism maintains the pH in the urine and the fluid that is inside the cells. The buffer consists of inorganic phosphates: monobasic (acts as an acid) and dibasic (acts as an alkali). At 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 an acid. This mechanism is more acidic than alkaline, so it perfectly neutralizes acidic metabolites, such as lactic acid, entering the human bloodstream.
Features of the protein buffer
Protein buffer does not play such a special role in stabilizing the acid-base balance, compared to other systems. It accounts for about seven percent of the total buffer capacity. Proteins are made up of molecules that combine to form 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, whichit is quite effective at a pH value of 7.2 to 7.4. A large proportion of proteins are represented by albumins and globulins. Since the protein charge is zero, at normal pH it is in the form of alkali and s alt. This buffer capacity depends on the number of proteins, their structure and free protons. This buffer can neutralize both acidic and alkaline products. But its capacity is more acidic than alkaline.
Features of erythrocytes
Normally, erythrocytes have a constant pH - 7, 25. Hydrocarbonate and phosphate buffers have an effect here. But in terms of power, they differ from those in the blood. In erythrocytes, the 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 pH value inside the erythrocytes. The protein buffer in erythrocytes is closely related to the bicarbonate system, since the ratio of acid and s alt here is less 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 s alt retains a stable value. Even if you add acid or alkali to them, the acid-base balance will not change. As an example, consider the acetate buffer, which consists of the acid CH3COOH and its s alt CH3COO. If you add a strong acid, then the base of the s alt will bind the H + ions and turn into acetic acid. S alt anion reductionbalanced by an increase in acid molecules. As a result, there is little change in the ratio of the acid to its s alt, so the pH changes quite imperceptibly.
Mechanism of action of buffer systems
When acidic or alkaline products enter the bloodstream, the buffer maintains a constant pH value until the incoming products are excreted or used in metabolic processes. There are four buffers in human blood, each of which consists of two parts: an acid and its s alt, as well as a strong alkali.
The effect of the buffer is due to the fact that it binds and neutralizes the ions that come with the composition corresponding to it. Since in nature the body most of all encounters under-oxidized metabolic products, the properties of the buffer are more anti-acid than anti-alkaline.
Each buffer system has its own principle of operation. When the pH level drops below 7.0, their vigorous activity begins. They begin to bind excess free hydrogen ions, forming complexes that move oxygen. It, 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 excretion.
In the human body, only four buffer systems play an important role in maintaining acid-base balance, but there are other buffers, such as the acetate buffer system, which has a weak acid (donor) and its s alt (acceptor). The ability of these mechanismsto resist changes in pH when acid or s alt enters the blood is limited. They maintain acid-base balance only when a strong acid or alkali is supplied in a certain amount. If it is exceeded, the pH will change dramatically, the buffer system will cease to function.
Buffers efficiency
Buffers of blood and erythrocytes have different efficiency. In the latter, it is higher, since there is a hemoglobin buffer here. The decrease in the number of ions occurs in the direction from the cell to the intercellular environment, and then to the blood. This suggests that the largest buffer capacity is in the blood, and the intracellular environment has a smaller one.
When cells are metabolized, acids appear that pass into the interstitial fluid. This happens the easier, the more of them appear in the cells, 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 still play a role here, which react by swelling to the accumulation of acid, they absorb it and release erythrocytes from hydrogen ions. This ability is due to its absorption property.
Interaction of buffers in the body
All the mechanisms that are in the body are interconnected. Blood buffers consist of several systems, the contribution of which to maintaining the acid-base balance is different. When blood enters the lungs, it receives oxygen.by binding to hemoglobin in red blood cells, forming oxyhemoglobin (acid), which maintains the pH level. With the assistance of carbonic anhydrase, there is a parallel purification of the blood of the lungs from carbon dioxide, which in erythrocytes is presented in the form of a weak dibasic carbonic acid and carbaminohemoglobin, and in the blood - carbon dioxide and water.
With a decrease in the amount of weak dibasic carbonic acid in erythrocytes, it penetrates from the blood into the erythrocyte, and the blood is cleansed of carbon dioxide. Thus, a weak dibasic carbonic acid constantly passes from the cells into the blood, and inactive chloride anions enter the erythrocytes from the blood to maintain neutrality. As a result, red blood cells are more acidic than plasma. All buffer systems are justified by the proton donor-acceptor ratio (4:20), which is associated with the peculiarities of the metabolism of the human body, which forms a greater number of acidic products than alkaline ones. The indicator of acid buffer capacities is very important here.
Exchange processes in tissues
Acid-base balance is maintained by buffers and metabolic transformations in body tissues. This is assisted by biochemical and physico-chemical processes. They contribute to the loss of acid-base properties of metabolic products, their binding, the formation of new compounds that are quickly excreted from the body. For example, a large amount of lactic acid is excreted into glycogen, organic acids are neutralized by sodium s alts. Strongacids and alkalis dissolve in lipids, and organic acids oxidize to form carbonic acid.
Thus, the buffer system is the first assistant in the normalization of 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 introduction and removal of hydrogen and carbon dioxide ions, which helps maintain a constant pH level in the blood.
If there is a failure in the work of buffer systems, then a person develops pathologies such as alkalosis or acidosis. All buffer systems are interconnected and aimed at maintaining a stable acid-base balance. The human body constantly produces a large number of acidic products, which is equivalent to thirty liters of strong acid.
The constancy of reactions inside the body is provided 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 develop various pathologies that can lead to coma or death.
