The three main functions of a mammal’s hair are: _, _, and _.

The three main functions of hair are typically protection, body temperature regulation, and the facilitation of evaporation of the bodies perspiration.

Mitochondria produce atp, a high energy compound. atp is used for all sorts of enzyme-mediated reactions, such as making proteins/nucleotides/etc, certain compounds cross the cell membrane, muscles move, etc.  without this source of energy, a cell will die. it will not be able to repair itself, defend against pathogens, etc.