WHAT ARE BUFFERS?

Buffer is a substance that can act to keep body fluid pH at normal levels (pH 7.35-7.45)

  Can react in two ways: as an acid (releasing a hydrogen ion) or as a base (binding a hydrogen ion)

  Buffers always try to bring the fluid as close as possible to the normal body fluid pH of 7.35 to 7.45

o   If the fluid is basic (with few free hydrogen ions), the buffer releases hydrogen ions into the fluid

o   If the fluid is acidic (with many free hydrogen ions), the buffer acts as a base, binding some of the excess hydrogen ions

TYPES OF BUFFERS 

1. Chemical buffers

·        Usually a weak base and an acid salt

·        Most common chemical buffers:

o   Bicarbonate (active in both extracellular fluid [ECF] and intracellular fluid [ICF])

o   Phosphate (active in ICF)

2. Protein buffers

·      -  Most common buffers

·        - Proteins in body fluids can either bind or release free hydrogen ions as needed

·       -  Both ICF and ECF proteins serve as buffers

o   Extracellular protein buffers are albumin and globulins

·                                             Major cell protein buffer is hemoglobin

o   Hemoglobin buffers hydrogen ions directly and also buffers acids formed during the production of carbon dioxide

o   Free hydrogen ions in blood increase à excess hydrogen ions cross membranes of RBC à hydrogen ions bind to the large numbers of hemoglobin molecules in each RBC à decrease in hydrogen ions in blood à increase in pH back to normal