Demand-only energetics at 120 ATP per glucose: A reply to Lynch

Recently in these pages, a paper by Lynch appeared in response to a report showing that his numbers for biosynthetic costs (ATP demand) in cells are inflated, so much so that they would require E. coli to obtain >100 ATP per glucose and mitochondria to obtain >240 ATP per glucose. The inflated estimates trace to one factor: Lynch exclusively considers ATP demand and systematically neglects ATP supply-the essence of bioenergetics. Thermodynamics stipulate that a cell cannot grow if its ATP demands exceed its ATP supply. Here I compare Lynch's calculated ATP demands to laboratory measurements of the ATP supply that E. coli synthesizes during cell division. The results bear out my case, and leave no doubt: Lynch's calculations require E. coli to synthesize ∼120 ATP per glucose, which is thermodynamically impossible. As a consequence, his demand-only 'energetic' attacks on mitochondria and endosymbiosis in evolution are baseless.