Nester's Microbiology 8th Edition by Denise Anderson,Sarah Salm,Deborah Allen

Exercise 3

Cells use catabolic pathways to gradually oxidize an energy source, releasing energy that they then capture. A specific enzyme catalyzes each step of a pathway. Substrate-level phosphorylation uses exergonic chemical reactions to synthesize ATP; oxidative phosphorylation uses a proton motive force to do the same. Reducing power in the form of NADH and FADH₂is used to generate a proton motive force; the reducing power of NADPH is used in biosynthesis. Precursor metabolites are metabolic intermediates that can be used in biosynthesis. The central metabolic pathways generate ATP, reducing power, and precursor metabolites.
Why does fermentation supply less energy than cellular respiration?