What is the unity of assimilation and dissimilation?

Assimilation is the process by which the body incorporates nutrients from outside its body into the more complex structures needed within it. The simplest life form, the unicellular organism, does this through direct absorption through the cell wall. In multicellular organisms such as plants and animals, the process is different and becomes more complex in more complex life forms.

Dissimilation is the opposite of assimilation process in metabolism, which performs the function of decomposition of organic compounds and conversion from proteins, nucleic acids, fats, and carbohydrates into simple substances. A number of dissimilation processes – respiration, fermentation and glycolysis – play a central role in metabolism. Metabolism is the unity of assimilation and dissimilation.