30.14
Sistema tampón de fosfato
El sistema tampón de fosfato es un mecanismo biológico fundamental para mantener la estabilidad del pH en el cuerpo. Este sistema funciona principalme…
El sistema tampón de fosfato es vital en la orina y el líquido intracelular.
Se compone de dihidrógeno fosfato de sodio y fosfato de hidrógeno de sodio.
Dado que el dihidrógeno fosfato de sodio es un ácido débil, no se disocia mucho en soluciones ácidas y neutras.
Sin embargo, cuando se introduce una base fuerte, como el hidróxido de sodio, en la solución, el fosfato de dihidrógeno de sodio se disocia para ceder iones de hidrógeno. Estos iones se unen con los iones de hidróxido, formando moléculas de agua.
Al mismo tiempo, también se forma hidrogenofosfato de sodio.
Dado que este proceso convierte el hidróxido de sodio en la base débil de hidrógeno fosfato de sodio, el pH de la solución aumenta solo modestamente.
El hidrogenofosfato de sodio no se disocia en condiciones alcalinas.
Pero, cuando se agrega un ácido fuerte como el ácido clorhídrico a la solución, el hidrogenofosfato de sodio absorbe los iones de hidrógeno, formando el dihidrógeno fosfato de sodio.
Dado que este proceso convierte el HCl en el ácido débil dihidrógeno fosfato de sodio, el pH de la solución se reduce solo ligeramente.
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Q1: What are the two main components of the phosphate buffer system?
The phosphate buffer system consists of sodium dihydrogen phosphate (NaH2PO4), which acts as a weak acid, and sodium hydrogen phosphate (Na2HPO4), which serves as a weak base. These two components work together to neutralize both strong acids and strong bases, maintaining pH stability in urine and intracellular fluid.
Q2: How does the phosphate buffer respond when a strong base is added?
When a strong base like sodium hydroxide is introduced, sodium dihydrogen phosphate donates hydrogen ions that bind with hydroxide ions, forming water molecules. This converts the strong base into sodium hydrogen phosphate, a weak base, so the pH rises only modestly instead of dramatically.
Q3: What happens to the phosphate buffer when a strong acid is added?
When a strong acid like hydrochloric acid is added, sodium hydrogen phosphate accepts hydrogen ions and forms sodium dihydrogen phosphate. This converts the strong acid into a weak acid, causing only a slight pH reduction rather than a significant drop.
Q4: Why doesn't sodium dihydrogen phosphate dissociate in neutral or acidic solutions?
Sodium dihydrogen phosphate is a weak acid that does not fully dissociate under neutral or acidic conditions. It remains largely intact in these environments, but when exposed to strong bases, it readily donates hydrogen ions to neutralize the base and stabilize pH.
Q5: Where does the phosphate buffer system function in the body?
The phosphate buffer system is vital in urine and intracellular fluid, playing a critical role in renal physiology. It helps excrete hydrogen ions and stabilize urine pH, contributing to the body's overall acid-base balance through renal regulation of acid base balance.
Q6: What is the relationship between sodium hydrogen phosphate and strong acids?
Sodium hydrogen phosphate, the weak base component, neutralizes strong acids by accepting hydrogen ions released by the acid. This reaction binds excess hydrogen ions and converts the strong acid into sodium dihydrogen phosphate, a weak acid, preventing significant pH reduction.
Q7: How does the phosphate buffer system maintain pH stability?
The phosphate buffer system minimizes pH changes through its dual capacity to neutralize both strong acids and strong bases. By converting strong acids into weak acids and strong bases into weak bases, it effectively stabilizes the solution's pH even when significant amounts of acid or base are introduced.