Figure 3.

Different modes of the pentose phosphate pathway (PPP). The PPP can operate in different modes depending on cellular requirements of NADPH and ribose 5-phosphate. Mode 1 primarily generates ribose 5-phosphate by funneling glycolytic intermediates into the nonoxidative stage of PPP. Mode 2 produces balance of both NADPH and ribose 5-phosphate. Mode 3 produces primarily NADPH as the ribose 5-phosphate is funneled into glycolysis to go back into the oxidative stage of PPP for further generation of NADPH. Mode 4 generates NADPH and the ribose 5-phosphate is funneled into glycolysis to generate ATP. (Adapted, with permission, from Berg et al. 2012, © W.H. Freeman and Company.)