Instructions: You are given a passage. You need to construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) its answer is the whole paragraph. Avoid creating questions that can be answered correctly without actually understanding the paragraph.
Input: Titratable Acidity
H+ is produced from CO2 and H2O (as in the proximal tubular cells) and actively transported into the distal tubular lumen via a H+-ATPase pump. Titratable acidity represents the H+ which is buffered mostly by phosphate which is present in significant concentration. Creatinine (pKa approx 5.0) may also contribute to TA. At the minimum urinary pH, it will account for some of the titratable acidity. If ketoacids are present, they also contribute to titratable acidity. In severe diabetic ketoacidosis, beta-hydroxybutyrate (pKa 4.8) is the major component of TA.

The TA can be measured in the urine from the amount of sodium hydroxide needed to titrate the urine pH back to 7.4 hence the name 'titratable acidity'.
Output:
what is titratable acidity, how is it formed in the kidney and excreted in the urine?