Question

Which of the following accounts for the intracellular fluid buffering system?

1. all of the choices are correct

2. Bicorbonate-Carbonic Acid Buffer system

3. Protein Buffer system

4. Phosphate Buffer System

Answer 1

A all of the choices are correct

• H2CO2 : HCO3- is not an important true buffer system because normal blood pH i.e 7.4 is so far from its pK (6.1).
• H2CO3 and HCO3- are involved in pH control but they are not acting as a buffer system

• Proteins are the most important buffers in the body.
• They are mainly intracellular and include haemoglobin.
• The plasma proteins are buffers but the absolute amount is small compared to intracellular protein.
• Protein molecules possess basic and acidic groups which act as H+ acceptors or donors respectively if H+ is added or removed.

• Phosphate buffer is mainly intracellular.
• The pK of this sytem is 6.8 so that it is moderat ely efficient at physiological pH's.
• The concentration of phosphate is low in the extracellular fluid but the phosphate buffer system is an important urinary buffer.