text: I am not sure what you mean by preparation.  Basically lipids (fatty acids) are cleaved to produce long carbon chains which are then broken down (via lipolysis not via glycolysis).  Proteins are broken down via proteases and enter the cell as free amino acids or small peptides, which can be converted to energy.\n\nProteins and lipids can be converted to glucose (which is broken down via glycolysis) via gluconeogenesis, but they first have to be broken down.