What Citric Acid intermediate links glycolysis and gluconeogenesis together?
Answers
Answer:
The link between glycolysis and the citric acid cycle is the oxidative decarboxylation of pyruvate to form acetyl CoA. In eukaryotes, this reaction and those of the cycle take place inside mitochondria, in contrast with glycolysis, which takes place in the cytosol.
Answer:
Glycolysis and gluconeogenesis are metabolic processes responsible for glucose degradation or glucose synthesis respectively. In glycolysis, the breakdown of glucose molecules generates two net adenosine triphosphate (ATP) molecules, which provide a readily available source of energy for various reactions in the cell, and two pyruvate molecules, which can be further converted into lactate (used in gluconeogenesis), acetyl-CoA (used in citric acid cycle), oxaloacetate (used in citric acid cycle), and alanine (used in transamination reactions). Glycolysis, which occurs exclusively in the cytoplasm, is the sole source of ATP in cells that lack mitochondria (e.g., red blood cells). In gluconeogenesis, glucose, which ensures euglycemia during fasting, is synthesized from noncarbohydrate precursors such as glucogenic amino acids (mainly alanine and glutamine), odd-chain fatty acids, glycerol, pyruvate, and lactate. While the glycolytic pathway occurs in all cells, gluconeogenesis occurs almost exclusively in the liver. Phosphofructokinase-1 is the rate-limiting enzyme for glycolysis, while fructose 1,6-bisphosphatase is the rate-limiting enzyme for gluconeogenesis. The metabolism of glucose is mainly controlled by hormones such as insulin, which stimulates glycolysis, and glucagon, which stimulates gluconeogenesis. Glucose can also be shunted to the pentose phosphate pathway (also known as the hexose monophosphate shunt), which is a metabolic pathway that generates nicotinamide adenine dinucleotide phosphate (NADPH) and ribose 5-phosphate from glucose 6-phosphate. The pentose phosphate pathway occurs exclusively in the cytosol and is highly active in the adrenal cortex, liver, and red blood cells (RBCs). Ribose 5-phosphate is required for nucleotide synthesis, while NADPH is required for cholesterol synthesis, steroid synthesis, reduction of glutathione, and respiratory burst. Glucose 6-phosphatedehydrogenase deficiency results in hemolytic anemia due to insufficient production of NADPH, which is required for the reduction of the antioxidant glutathione to prevent excess hydrogen peroxide and free radicals from damaging RBC membranes.