Glucose can also serve as the initial molecule for two alternative pathways to glycolysis.


 

In the pentose-phosphate pathway, five-carbon products of the substrate-level phosphorylation of glucose are used in the biosynthesis of nucleotides, amino acids and glucose during photosynthesis.   Only 1 ATP is generated by this pathway, rather than the two generated by glycolysis.


The Entner-Doudoroff pathway, utilized by bacteria such as Pseudomonas aeruginosa and Enterococcus faecalis, also generates only 1 ATP.  It uses different enzymes and produces different precursor molecules than those of glycolysis or the pentose-phosphate pathways and generates NADPH, not found in either of the others.