The pH of blood and tissue fluid I human remains constant at about 7.4 in spite of metabolic activities which produce hydrogen ions. Explain how this constancy is maintained by the kidney.
- In the cells of proximal convolute tubule, carbon dioxide reacts with water to form carbonic acid. the reaction is catalyzed by carbonic anhydrase enzyme
- Carbonic acid dissociated into hydrogen and bicarbonate ions.
- The hydrogen ions are pumped into the lumen by an ATP dependent Na+/H+
- Here hydrogen ions are buffered by sodium hydrogen phosphate to form sodium dihydrogen phosphate.
- When the pH of the renal fluid falls too low, the cells of the distal convoluted tubules produce ammonia from glutamine.
- Ammonia combines with excess hydrogen ions to form ammonium ions that are excreted.
- When the pH of renal fluid rises too high, the cells of distal convoluted tubules excrete bicarbonate ions and retain hydrogen ions
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