pH Buffering in Human Blood

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This Demonstration simulates the buffer system in human blood, showing its resistance to a change in pH by the addition of acid or base. Human blood contains carbonic acid and bicarbonate anion , which form a buffer to maintain blood pH between 7.35 and 7.45.


Move the sliders to control the acid or base added to the buffer system. The pH is calculated using the Henderson–Hasselbalch equation: . The pH is plotted as a function of concentration. The smiley face changes according to the pH value: it smiles only when the pH is within the healthy range. A yellow sad face means that the person is experiencing acidosis; a blue sad face means alkalosis.


Contributed by: Claire Chen and Hongdi Wu (August 2022)
With additional contributions by: Dalia Hassan, Yifan Lai and Kristina M. Lenn
Open content licensed under CC BY-NC-SA



[1] J. Pietri and D. Land. "Blood as a Buffer." (Nov 24, 2021)

[2] Wikipedia. "Bicarbonate Buffer System." (Nov 24, 2021)

[3] Khan Academy. "Chemistry of Buffers and Buffers in Our Blood." (Nov 24, 2021)

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