The cells of are continuously functioning -- synthesising , storing , secreting, multiplying and so on. For all these functions to take place properly, it is necessary to control the pH of the cells and the body fluids. We hnow that pH is controlled by H^+ ion concentration. Enzyme action is specially affected by any change in pH as it can affect the positively and negatively charged groups of the enzyme molecule. This, in turn, affects the three dimentional structure of protein and hence its activity. For these reasons it is essential to control the pH of the internal environment of the body.
Buffers are chemicals or a combination of chemicals that tend to prevent any changes in the hydrogen ion concentration in the body. Buffers generally composed of mixtures of weak acid and their corresponding salts .
You have to do pH and buffer laboratory to study the buffering system in living organisms. For example, during heavy physical exercise, lactic acid is produced in the muscle cells. This changes the hydrogen ion concentration and this is buffered by bicarbonates. Perhaps this is why atheletes take a dose of sodium biarbonate to delay muscle fatigue and increase muscle efficiency.
In the lab you are taught buffering by the procedure of titration. The most common is the Sodium Phosphate Titration.
A sample of 20ml sample of Na3PO4 is titrated after setting up the burette, the stirrer and the electrode After the phosphate titration the pH meter is calibrated first with pH standard buffer. Also to cover the entire pH scale , two samples are titrated, one with HCl and the other with NaOH.