Question

The pH of the blood is maintained by balancing the ratio of
A. Lactic acid and Pyruvic acid
B. $NaHCO_3$ and $H_2CO_3$
C. $CO_2$ and $H_2O$
D. Pyruvic acid and $H_2CO_3$

Answer 1

The buffer systems present in the blood are constituted by phosphates, plasma proteins, carbonic acids and bicarbonates. It helps in maintaining the pH of the blood. The correct pH is very important in gaseous exchange and gas transport.

Step by step answer: Bicarbonate buffering system helps in maintaining acid base homeostasis. Here, pH is maintained by $NaHCO_3$ (sodium bicarbonate) and $H_2CO_3$ (carbonic acid). In the buffering system, carbon dioxide combines with the water to produce carbonic acid ($H_2CO_3$). This is unstable and undergoes rapid dissociation to hydrogen cation and bicarbonates anion. The reaction is reversible and carbonic anhydrase catalyzes this reaction.
pH of the blood is between 6.8 to 7.8 which is maintained by the activity of sodium bicarbonate and carbonic acid. An increased concentration of carbonic acid leads to an increased acidity of the blood. As a compensatory mechanism, the breathing gets deeper which helps in elimination of excess carbon dioxide produced. The alkaline buffer produced by sodium bicarbonate ensures that the blood gets neutralized.
Considering the other given options
Pyruvic and lactic acid are involved in respiration which can be both aerobic and anaerobic. Pyruvic acid helps in energy production through Krebs cycle and Lactic acid is the end product for anaerobic respiration and happens mostly on exertion in the muscle tissues.
The other options do not play a role in the management of the pH of the blood in combination.
Thus, the most appropriate answer is B.

Note: During workouts, muscles of the human body have loss of oxygen to undergo a normal aerobic respiration process, and choose an alternative pathway to respire anaerobically. The end product of this reaction is lactic acid, which gets accumulated in the muscles and leads to the development of muscle cramps.