Glicerólisis

Glicerólisis is a fundamental metabolic pathway that breaks down glucose, a simple sugar, into pyruvate. This process occurs in the cytoplasm of virtually all living cells, both prokaryotic and eukaryotic. Glicerólisis is the initial stage of cellular respiration, and it can proceed with or without oxygen, depending on the organism and its metabolic state.

The pathway involves a series of ten enzymatic reactions. In the first phase, called the energy investment phase, two molecules of ATP are consumed to destabilize the glucose molecule. This prepares glucose for cleavage into two three-carbon sugar phosphates. In the second phase, the energy payoff phase, these three-carbon molecules are oxidized and rearranged, yielding a net production of four ATP molecules and two molecules of NADH. Therefore, the overall net gain from one molecule of glucose is two ATP and two NADH.

The pyruvate produced by glicerólisis can enter different fates. In the presence of oxygen, it proceeds to the Krebs cycle and oxidative phosphorylation, yielding a large amount of ATP. In the absence of oxygen, or in certain anaerobic organisms, pyruvate can be converted into other products through fermentation, such as lactate or ethanol. This fermentation process regenerates NAD+ from NADH, allowing glicerólisis to continue. Glicerólisis is a crucial source of energy for cells, especially when oxygen is limited.