Figure 1.

Schematic representation of glycolysis and the tricarboxylic acid (TCA) cycle (A) During glycolysis, two molecules of adenosine triphosphate (ATP) are consumed and four are produced, resulting in a gain of two molecules of ATP per one molecule of glucose. In addition, two molecules of nicotinamide adenine dinucleotide (NADH) are also generated. Under hypoxic conditions, pyruvate is further fermented into lactate resulting in the regeneration of two molecules of NAD⁺ that can be used again in glycolysis. (B) Under normoxic conditions, pyruvate is converted to acetyl-CoA in the mitochondria, which then enters the TCA cycle, where two turns are needed to process one molecule of glucose leading to the generation of two molecules of ATP, six NADH and two flavin adenine dinucleotide (FADH₂). Triangles indicate enzymes. Abbreviations: (A) GLUT1; glucose transporter 1, HK2; hexokinase 2, PKF1; phosphofructokinase 1, PGK; phosphoglycerate kinase, PK; pyruvate kinase, LDH; lactate dehydrogenase, PDH; pyruvate dehydrogenase, PDKs; pyruvate dehydrogenase kinases. (B) CS; citrate synthase, ACO2; aconitase, IDH; isocitrate dehydrogenase, OGDC; oxoglutarate dehydrogenase, SCS; succinyl-CoA synthase, SDH; succinate dehydrogenase, FM; fumarate hydratase, MDH; malate dehydrogenase.