What is the purpose of the buffer systems of living organisms and what is the principle of their functioning?

Buffer systems maintain a certain pH (acidity indicator) of the medium in biological fluids. The principle of operation is that the pH of the medium depends on the concentration of protons in this medium (H +). The buffer system is capable of absorbing or releasing protons depending on their entry into the medium from the outside or, on the contrary, removal from the medium, while the pH will not change. The presence of buffer systems is necessary in a living organism, since due to changes in environmental conditions, the pH can vary greatly, and most enzymes work only at a certain pH value.
Examples of buffer systems:
carbonate-bicarbonate (mixture of Na2CO3 and NaHCO3)
phosphate (a mixture of K2HPO4 and KH2PO4).

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