What happens when cellular respiration is not working properly? Disease. Scientists are still studying the connections between glycolysis, cellular respiration and disease, but some interesting links exist. For example, Alzheimer's may be linked to "aerobic glycolysis," which is when cells use glucose that does not go into oxidative phosphorylation.
Tumor cells have an interesting way that they can get energy: instead of oxidative phosphorylation (the electron transport chain and such), tumor cells do something called aerobic glycolysis. Aerobic glycolysis makes lactic acid, so it is like fermentation…except it is done with oxygen. This is a pretty inefficient process, which means cancer cells have to use way more glucose than healthy cells to survive and reproduce.
When a cancerous cell changes its metabolism from normal metabolism to aerobic glycolysis, it is called the Warburg effect, after the scientist and Nobel laureate that discovered it. Dr. Warburg thought that this type of metabolism might be what drives cancer. But it's a hot topic of research. Scientists are currently trying to figure out if aerobic glycolysis is a cause or effect of cancer (Taubes 2012). In other words, which came first, the chicken or the egg?
Alzheimer's disease might also be linked to aerobic glycolysis. Research has linked high levels of aerobic glycolysis in the brain to deposition of plaques later in life (Vlassenko et al. 2010). We all know plaque on our teeth is bad news. After all, dentists insist that we remove our plaque daily with toothbrushes. Plaques in the brain are to blame for Alzheimer's. Since they don't make brain brushes yet, researchers will have to keep looking for a cure.
Leigh's syndrome is a rare neurological disease in children in which the central nervous system degenerates, and as the disease progresses motor skills and muscle development weaken. Although not totally understood, Leigh's syndrome is related to problems with cellular respiration. Breakdowns in both the electron transport chain and the conversion of pyruvate to acetyl CoA have been implicated as causes of Leigh's. Cells in Leigh's syndrome patients have slower metabolisms, and take up less oxygen and glucose than healthy cells. In some cases, Leigh's syndrome has been treated successfully with certain vitamins that are necessary cellular respiration such as thiamin, coenzyme Q10, and vitamins C, K3 and E. (Vo et al. 2007).