Question

If pH of blood is artificially changed to 8, what is most likely to happen?

• A. The tissues will not get oxygen as oxyhaemoglobin will not dissociate into oxygen and haemoglobin.
• B. The carbon dioxide will not be released from carbonic acid and carbonates.
• C. The carbonic anhydrase will be completely inhibited.
• D. It will generate carbon monoxide and the animal will die of carbon monoxide poisoning.

Answer 1

The correct option is C The carbonic anhydrase will be completely inhibited.

In the human body, there is an important buffering system in acid-base homeostasis known as the 'bicarbonate buffering system'. Being a buffer, it maintains the plasma pH (7.35 - 7.45) and would counteract any force that can alter the system.
The reaction of the system is as follows:
CO${}_2$ + H${}_2$O --> H${}_2$CO${}_3$ --> HCO${}_3^{-}$ + H${}^{+}$
This is a reversible reaction, where the carbon dioxide combines with water to form carbonic acid, which in turn rapidly dissociates to form hydrogen ions and bicarbonate ions. This reaction is catalyzed by the enzyme carbonic anhydrase. This enzyme has its optimum activity at the physiological pH.
If the pH goes high (8) or on an alkaline side, the activity of the enzyme will be inhibited.
Thus, the correct answer is option (C).