The explanation is that cell A was fermented (anaerobically), and cell B proceeded with cellular respiration (aerobic).
Lactic fermentation is a catabolic process, a fermentation, having as a starting point glycolysis, which produces an acid, lactic acid used to reoxidize NADH. In other words, lactic acid fermentation is a biological process by which sugars such as glucose, fructose, and sucrose are converted into cellular energy and metabolic byproduct, lactate. It is a lactic ferment that intervenes.
Each molecule of glucose completely oxidized by cellular respiration is likely to produce 38 ATP molecules: 2 ATP from glycolysis, 2 ATP from the Krebs cycle, and 34 ATP from the respiratory chain. This nominal efficiency, however, is never reached because of losses by dissipation of the electrochemical gradient through the inner membrane of mitochondria as well as because of the energy cost of active transport of pyruvate from the cytosol to the mitochondrial matrix, so that the current estimates are around 30 to 32 molecules of ATP formed by oxidized glucose molecules.
