Most students overcomplicate acid–base balance, but it’s one of the most high-yield topics on the MCAT. Here’s the breakdown:

Your blood pH stays tightly regulated around 7.4. Even small shifts can disrupt enzyme function and metabolism, so your body uses buffer systems to stay in balance.

The bicarbonate buffer system is the main player—CO₂ and HCO₃⁻ act like a seesaw. When acid builds up, bicarbonate binds it. When things get too basic, carbonic acid releases H⁺ to restore balance.

From there, your respiratory system fine-tunes CO₂ levels, while your kidneys adjust bicarbonate. That’s how the body compensates during respiratory or metabolic acidosis and alkalosis.

Finally, the Henderson–Hasselbalch equation ties it all together:
pH = 6.1 + log (HCO₃⁻ / 0.03 × pCO₂).
It’s not about memorizing numbers—it’s about understanding how these systems work together to maintain homeostasis.

How confident are you in acid–base questions on the MCAT?