ATP is the key molecule that provides energy for cellular processes. Glucose can be metabolized via two integrated metabolic pathways, glycolysis and OxPhos, which efficiently convert glucose into ATP. Glycolysis converts glucose to pyruvate in the cytosol, generating two molecules of ATP. In the mitochondria, pyruvate is further metabolized to CO₂ by the KREBS cycle, which drives OxPhos and ATP synthase activity, generating up to 34 ATP per molecule of glucose. Cells can also metabolize alternative substrates, such as lipids and glutamine, which feed into the KREBS cycle to drive OxPhos and ATP synthesis. Aerobic glycolysis supports biosynthetic processes, as it allows the uptake of larger amounts of glucose and the maintenance of elevated glycolytic flux. Glycolytic intermediates are then diverted into other pathways for synthesis of biomolecules that support biosynthetic processes. For instance, glucose-6-phosphate (G6P) can feed into the pentose phosphate pathway (PPP), generating ribulose-5-phosphate (R5P) to support nucleotide synthesis. This pathway also generates NADPH, a cofactor that is essential for various biosynthetic processes, including lipid synthesis. Glucose can also be converted into cytoplasmic acetyl-CoA via citrate in the KREBS cycle for the production of cholesterol and fatty acids. Glycolytic intermediates are also converted into other biomolecules for protein and lipid synthesis. Glutamine feeds into the KREBS cycle and can also supply biomolecules for biosynthetic processes under certain conditions. F6P, fructose-6-phosphate; DHAP, dihydroxyacetone phosphate; G3P, glyceraldehyde 3-phosphate; BPG, 2,3-bisphosphoglycerate; GP, glycerate 3-phosphate; OAA, oxaloacetate.