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.
| Complex Food Molecule |
Basic Units |
| Proteins |
Amino Acids |
| Polysaccharides |
Simple Sugars (e.g. glucose) |
| Fats (Lipids) |
Fatty Acids and Glycerol |
Go on to Stage 2: Glycolysis
| 
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