Buffer

[Ref: KB's online acid-base text]

A buffer is a solution containing substances which have the ability to minimise changes in pH when an acid or base is added to it.

 

Major body buffer systems

ISF

• HCO3
  * Important for metabolic acid

NB:

• Phosphate and protein concentration too low

Blood

• HCO3
  * Important for metabolic acid
• Hb
  * Important for CO2
• Plasma protein
  * Minor

NB:

• Phosphate concentration too low

Intracellular fluid

• Protein
  * Important buffer
• Phosphate
  * Important buffer

Urine

• Phosphate
  * Most of the titratable acid
• Ammonia
  * Formation of NH4+

Bone

• Calcium carbonate
  * Important in prolonged metabolic acidosis

 

Bicarbonate buffering system

Most important buffering system

Contributes 80% of buffering in ECF

Buffers metabolic acidosis
* But cannot buffer respiratory acidosis