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MBBS QUESTION #10378
Question 1
Despite the relatively modest concentration of plasma bicarbonate compared to the large daily acid load generated by normal metabolism, the body maintains blood pH within a remarkably narrow range. This is best explained by:
  • The combined, simultaneous action of multiple buffer systems (bicarbonate, phosphate, protein/hemoglobin), together with rapid respiratory CO2 elimination and slower renal net acid excretion and bicarbonate regeneration, all acting together to maintain pH homeostasis✔️
  • The body having no meaningful buffering capacity and relying entirely on renal excretion alone
  • The phosphate buffer system acting as the sole physiologically relevant buffer
  • Blood pH being entirely independent of any buffering mechanism
Correct Answer Explanation
Acid-base homeostasis depends on the integrated, layered action of chemical buffers (providing an immediate response), the respiratory system (adjusting CO2 elimination within minutes), and the kidneys (regenerating bicarbonate and excreting net acid over hours to days) — together allowing the body to absorb a substantial daily acid load while keeping blood pH within a narrow physiological range.