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Acid-base balance
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pH measures how acidic or how alkaline a liquid is. Blood lives in a narrow band, between 7.35 and 7.45. Below 7.35 it is called acidemia, and above 7.45, alkalemia.
Two systems push it back. The lungs do it by removing carbon dioxide with every exhalation, and when they compensate for a metabolic disorder they work fast: minutes to hours. The kidneys do it another way, by reabsorbing bicarbonate, the substance that buffers acid, and excreting the fixed acids in the urine, the ones the lungs cannot exhale. That one takes days. They are two valves on different clocks: the lung valve turns in hours, the kidney valve in days.
And if pH leaves that band, things stop working. Proteins denature, meaning they lose the shape they need in order to work. And hemoglobin, the protein that carries oxygen inside the red blood cell, loses its affinity for oxygen when pH falls: it releases it more easily.
In brief
Acid-base balance keeps the body's pH between 7.35 and 7.45: below that is acidemia, above it is alkalemia.
When compensating for a metabolic disorder, the lungs blow off carbon dioxide and correct within minutes to hours; the kidneys, by reabsorbing bicarbonate and excreting fixed acids, take days.
Two valves on different clocks: one turns in hours, the other in days.
Outside that range proteins denature, and as pH falls hemoglobin loses its affinity for oxygen.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Acid Base Balance, StatPearlsPublished
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