Glycolysis, the citric acid cycle, the oxidative deamination of neurotransmitters by monoamine oxidase, the breakdown of muscle protein to use amino acids as gluconeogenesis substrates, the breakdown of fat in adipose tissue to fatty acids, and the breakdown of fat in adipose tissue to fatty acids are all catabolic processes.The third stage is composed of.The digesting stage is the initial stage. Major organic molecules including proteins, lipids, and polysaccharides are digested outside of cells into their smaller components. In the third stage, energy is stored.