Chapter 1 - Glycolysis

Abstract

Glycolysis is a cytoplasmic pathway which breaks Glucose in two 3-carbon compounds and generates energy. Glycolysis is used by all the cells of the body for energy generation. Glucose is trapped by phosphorylation, with the help of Hexokinase enzyme. ATP is used in this reaction, and product Glucose-6-P inhibits Hexokinanse. This is irreversible reaction. G-6-P is isomerised into its ketose form Fructose-6-P by Phosphohexose isomerase. F-6-P is further phosphorylated by Phosphofructokinase to Fructose 1,6-bisphosphate. This reaction is irreversible and the principal regulatory step. Aldolase cleaves F1,6 bisP into Glyceraldehyde-3-P and DHAP which are interconverted by enzyme Phosphotriose isomerase. Glyceraldehyde-3-P is oxidised by NAD+-dependent dehydrogenase forming 1,3-bisphosphoglycerate. 1,3-bisphosphoglycerate has a high-energy acyl-phosphate bond and carries out substrate-level phosphorylation generating ATP. Enzyme participating is Phosphoglycerate kinase and 3-Phosphoglycerate is formed. Phosphoglycerate mutase isomerises 3-Phosphoglycerate to 2-phosphoglycerate. 2-phosphoglycerate is dehydrated by enolase to form Phosphoenolpyruvate, second compound capable of substrate-level phosphorylation in glycolysis. Pyruvate kinase transfers Phosphate group of Phosphoenolpyruvate to ADP, and pyruvate is formed. Pyruvate enters the Krebs cycle in aerobic conditions and in anaerobic conditions, it forms lactate which helps in generation of NAD+ for continuation of glycolysis. Pyruvate is converted to acetyl-CoA by Pyruvate Dehydrogenase Complex which is an irreversible step. Pyruvate enters the Krebs cycle for further energy production