Aerobic respiration is ultimately the reaction of glucose with oxygen to generate carbon dioxide, water, and energy. However, in a cell this process involves the transfer of electrons from glucose to carriers such as NAD over a lengthy series of steps. Why don't cells employ the direct reaction of glucose with oxygen to generate energy?

Cells don't employ the direct reaction of glucose with oxygen to generate energy because the direct transfer of electrons from glucose to oxygen occurs via a combustion reaction that is incompatible with life.

Explanation:

Aerobic respiration is a process by which chemical energy is released in cells during the breakdown of food e.g glucose.

Cells don't employ the direct reaction of glucose with oxygen to generate energy because the direct transfer of electrons from glucose to oxygen occurs via a combustion reaction that is incompatible with life.

NAD is used to temporarily store high energy electrons harvested from glucose molecules in a series of gradual steps in the cytoplasm.