Stage 1: Food Breakdown

Before food can be processed into ATP, large polymeric molecules must be broken down into their basic units. For example, proteins must be broken down into amino acids and polysaccharides must be broken down into glucose. This step is known as digestion. Most of digestion takes place in the digestive tract of animals and food is broken down by secreted enzymes. 

Even after all of the molecules have been broken down into their basic units, most of the non-glucose molecules are subsequently converted into glycose so that they can be processed during glycolysis. The following table lists the food molecules and there basic unit.

Go on to Stage 2: Glycolysis