Test: MCAT Biology

Among the most important pH buffer systems in humans is the bicarbonate buffer, which keeps the blood at a remarkably precise 7.42 pH.  The bicarbonate buffer system uses a series of important compounds and enzymes to make the system function.  Figure 1 depicts the key reactions that take place.

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The activity of this buffer system is mainly controlled by the renal and respiratory systems.  The renal system excretes bicarbonate in the urine, while the respiratory system “blows off” carbon dioxide as needed.   By balancing these two systems as needed, blood pH is maintained in such a narrow range.

12.

A patient undergoes a procedure in a hospital, and begins to reabsorb large quantities of bicarbonate from the kidneys. In the above reaction __________.

CO2 quickly builds up

the equilibrium is shifted toward bicarbonate

CO2 production will decrease, while carbonic acid concentration builds up

the equilibrium is shifted toward CO2

carbonic anhydrase prevents a shift in equilibrium

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