1. The document discusses kidney control of acid-base balance through secretion of hydrogen ions (H+) and generation of bicarbonate (HCO3-) in the extracellular fluid. 2. The kidney secretes H+ as sodium phosphate (NaH2PO4) and ammonium (NH4+) in the collecting duct, which allows regeneration of HCO3- for the extracellular fluid. 3. Glutamine breakdown in proximal convoluted tubule cells produces HCO3- and NH4+ during acidosis, with HCO3- reabsorbed and NH4+ secreted to help counter extracellular fluid acidosis.