What processes are included in the preparatory, cellular and final stages of metabolism?

Dissimilation, or energy metabolism, consists of three stages (for example, an animal cell):

1. Preparatory. It flows in the digestive organs (outside the cell). At this stage, starch breaks down to glucose, the energy released during this is dissipated in the form of heat;

2. Oxygen-free, or fermentation. It flows in the cytoplasmic matrix. At this stage, glucose is broken down to 2 PVC molecules and 2 ATP molecules.

3. Oxygen. It flows in the mitochondria. At this stage, PVCA decomposes to CO2, H2O and 36 ATP molecules.