Explain how buffer systems work in the blood and in the urine. Give an example o

Question

Explain how buffer systems work in the blood and in the urine. Give an example of a buffer system that works in the plasma and a different buffer system that works in the urine. Why are they necessary? That is, why is it so important to buffer the blood pH? What about the urine pH? What are the general limitations of buffers? Why doesn’t HCl work as a buffer? How does each of these systems respond to 1) elevated H+ concentration and 2) decreased H+ concentration? How do these systems react to high protein/low carbohydrate diets? To starvation?

Explanation / Answer

Buffers are substances which resist changes in the concentration of H+ and OH- ions. Buffering system consists of either week acid and its conjugate base or week base and its conjugate acid. Buffer solutions resists changes in pH of the solution by addition of either small quantities of strong acid or strong base (alkali).

The pH of human blood is 7.4. Most of the physiological process in humans takes place at optimal pH range (7.0 to 7.8) only. pH below 7 and above 7.8 causes death of the cells within minutes. So, buffers (both blood and urine) are essential for normal functioning of the body.

The buffer system that works in the blood are bicarbonate buffer, phosphate buffer and protein buffer. Buffer systems that functions in urine include bicarbonate buffer, ammonia buffer and phosphate buffer.

Buffers have limitations. The pH range of added acid or base should match with the capacity of the buffer. The other limitation is the limited solubility of acids, bases and their salts.

HCl is a strong acid. Cl ion in HCl is very stable. So, HCl cannot act as buffer. Buffers minimize the effect of either addition or removal of H+ concentration by binding or releasing H+ ions in response to concentration changes. When hydrogen ion concentration increases after addition of a strong acid, the weak base in a buffer binds and removes hydrogen ions from the solution.

High protein low carbohydrate diet and starvation leads to acidosis. Buffer systems in body cannot handle the amount of acid produced during this diet. Calcium loss occurs leading to osteoporosis and kidney stones. High acid in blood will also lead to high blood pressure, diabetes, gallstones and certain cancers.

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