In 1961, F. Jacob and J. Monod proposed the operon model to explain the genetic basis of enzyme induction and repression in prokaryotes. A few years later (1965), these two investigators were awarded the Nobel Prize for their most incisive work. Although Jacob and Monod's original operon model applied specifically to the regulation of the genes for lactose metabolism in [...]
The individual steps in the catabolism of carbohydrates are known in great detail. For the most part, cells break down carbohydrates by similar metabolic pathways whether they are plant cells, animal cells, or bacterial cells. The central pathway, glycolysis, found in most cells is outlined in Figure 10-2; however, there are alternative pathways for oxidizing carbohydrates. Sugars are cleaved from [...]
The reactions of glycolysis have no specific requirement for oxygen. Oxidation reactions do occur, such as the removal of two hydrogen's from glyceraldehyde- 3-phosphate, and NAD+ is reduced to NADH, but oxygen per se is not consumed. Under anaerobic conditions (i.e., in the absence of oxygen), pyruvate may be reduced to a variety of different compounds. Alcoholic fermentation (reactions 10-19 [...]