The citric acid cycle is an extremely complex metabolic pathway that is critical for energy production by living cells. Despite being complex it is highly reducible. Multiple different evolutionary mechanisms were involved in its evolution including horizontal gene transfer, gene duplication, domain, exon and sub-exon exchange, gene displacement and evolutionary opportunism. The citric acid cycle is an outstanding example of how complex pathways can be the product of a rich range of evolutionary tools.[p122]
Is the citric acid cycle irreducibly complex?
