ABSTRACT
Acids are removed from the body by lungs, kidneys and gastrointestinal tract. The most important buffer pair in extracellular fluid (ECF) is carbonic acid (H2CO3) and bicarbonate (HCO3-). The interaction between this buffer pair forms the basis of the measurement of acid–base balance. Carbon dioxide, produced by the oxidation of carbohydrates and triglycerides, forms the main acid load. The majority of the non-volatile or metabolic acids are derived from protein metabolism, primarily metabolism of exogenous protein in the form of methionine and phosphoproteins. Sulphuric acid is formed from sulphur-containing amino acids such as cysteine and methionine. Hydrochloric acid is formed from the degradation of lysine, arginine and histidine. Phosphoric acid is formed by the hydrolysis of phosphoproteins. Haemoglobin is present within the red blood cells, but is readily available for buffering extracellular acids. Functionally, buffers can be classified as either ‘bicarbonate’ or ‘non-bicarbonate’.
