VALIDITY OF MODULES. “Some modules, such as those for protein synthesis, DNA replication, glycolysis, and even parts of the mitotic spindle (the cellular machinery that ensures the correct distribution of chromosomes at cell division), have been successfully reconstituted in vitro. Others are intrinsically more difficult to reconstruct from purified components and, for these, other methods have established the validity of the module.”
https://www.nature.com/articles/35011540