Definition
The pH value indicates how acidic or basic a solution is. Usually the acid-base definition according to Brønsted is used: If particles can take up protons (H+ ions), then these are called proton acceptors, or bases; if particles can give off protons, then we speak of proton donors, or acids. Accordingly, the pH value depends on which substances are in a solution and how they react with each other.
Usually, pH-values vary between 0 and 14. If the pH is below 7, a solution is acidic; if the pH is above 7, we speak of a basic solution. A solution with pH 7, such as water, is neutral.
The stomach acid, for example, has a pH value of 1.0 (=strongly acidic), whereas the juice of the pancreas has a pH of about 8 (=basic). The pH value is strongly dependent on the composition of a solution: If the amount of acid increases, the solution becomes more acidic, the pH decreases and vice versa. For this reason, the pH value of the blood or the stomach, for example, can change depending on its location and metabolism.
It is also important that the pH value also has an influence on the activity of enzymes. While most enzymes are functional at a neutral pH, some enzymes, such as the digestive enzymes of the stomach, can only develop their function at a very low (i.e. acidic) pH. The pH value can also have a protective function against bacteria or pathogens.
PH value in blood
The pH value of the blood is important for many cell functions and should have a constant value between 7.35 and 7.45 to maintain good body function. To keep the pH constant, there are various buffer systems in the blood, the most effective of which is the carbonic acid buffer. Proteins, phosphate and hemoglobin also buffer the pH of the blood.
But what is a buffer? Most solutions become acidic when acid is added or basic when bases are added. Buffer solutions, on the other hand, can compensate well for the addition of an acid or a base within a certain range and can then keep the pH constant.
These buffer systems are extremely important because they allow the body to produce acids (waste products) without affecting the blood pH. If the buffer systems are not sufficient and the pH value falls below 7.35, then acidosis (=overacidification) is present. If the pH value exceeds 7.45, this is called alkalosis.
Acidosis and alkalosis can have serious consequences for the person affected, such as shortness of breath and circulatory arrest. To prevent this, the pH value of the blood is regulated by breathing and kidney function or kept constant by the buffer systems. Further detailed information to this topic receives you under: pH value in the bloodFallen by the metabolism increased protons out, then these can be compensated by increased abatmen by CO2 or by a decreased Bikarbonatausscheidung of the kidney.
On the other hand, the acid-base balance of the blood can also be brought out of balance by impairing kidney function or respiratory disorders. In this case a distinction is made between respiratory alkalosis/acidosis and metabolic alkalosis/acidosis. Respiratory alkalosis occurs when too much CO2 is breathed out, for example when hyperventilating.
Respiratory acidosis, on the other hand, occurs when not enough CO2 is breathed out, e.g. by breathing less. Metabolic alkalosis occurs when too many bases are produced or when acids are lost (e.g. when vomiting). Metabolic acidosis is mainly caused by renal insufficiency (too little acid excretion) or diabetes mellitus in the form of so-called ketoacidosis. Untreated, ketoacidosis can lead to coma and possibly death. To a certain extent, a metabolic derailment can be compensated by respiration and vice versa.
