Final answer:
The primary fuel of colonocytes is short chain fatty acids, which are produced by the fermentation of undigested carbohydrates by bacteria in the large intestine.
Step-by-step explanation:
Of the four major macromolecular groups that are processed by digestion, carbohydrates are considered the most common source of energy to fuel the body. Glucose, a type of sugar, is the primary fuel for ATP production in cells. Excess glucose can be stored as glycogen or converted into fat. On the other hand, short chain fatty acids are primarily used by colonocytes, the cells lining the colon, as their main fuel source. These fatty acids are produced by the fermentation of undigested carbohydrates by bacteria in the large intestine.