Glycolysis Glycolysis  is the metabolic pathway that converts glucose into pyruvate. The free energy released in this process is used to form the high-energy molecules ATP (adenosine triphosphate) and NADH (reduced nicotinamide adenine dinucleotide).  Glycolysis is a sequence of ten enzyme-catalyzed reactions. Most monosaccharides, such as fructose and galactose, can also be metabolized through this pathway

Glycolysis Glycolysis is an oxygen-independent metabolic pathway. The wide occurrence of glycolysis indicates that this pathway is conserved in evolution.

Glycolysis In most organisms, glycolysis occurs in the cytosol. The most common type of glycolysis is the Embden–Meyerhof–Parnas (EMP pathway), which was discovered by Gustav Embden, Otto Meyerhof, and Jakub Karol Parnas. Glycolysis also refers to other pathways, such as the Entner–Doudoroff pathway and various heterofermentative and homofermentative pathways.

Metabolic Fate of Pyruvate Pyruvate is the end Product of glycolysis

The pathway was discovered by identifying the intermediates

Glycolysis The 10 step Pathway

Glycolysis The 10 step Pathway

Energetics of Glycolysis ATP Consumption ( Preparatory phase) In first Priming Reaction, Glucose -> Glucose 6- Phosphate,  1 molecule of ATP is used. In second Priming Reaction, Fructose 6- phosphate -> Fructose 1,6-bisphosohate,  Total ATP Consumption: 2 molecules ATP Production ( Pay off phase) First ATP-forming Reaction (Substrate Level Phosphorylation),  1,3 bisphosphiglycerate -> 3 phosphoglycerate,  2 molecules of ATP are formed. Second ATP- forming Reaction (Substrate Level Phosphorylation),  Phosphoenolpyruvate -> Pyruvate,  2 molecules of ATP are formed. Total ATP Production : 4 molecules

Energetics of Glycolysis Net Yield : 4 ATP - 2 ATP = 2 ATP molecules In addition to it, Oxidation and Phosphorylation of Glyceraldehyde 3-phosphate -> 1,3 - bisphosphiglycerate is involved. In this step, 2 NAD molecules are consumed to form 2 NADH molecules. Therefore, 2 NADH molecules = 6 ATP molecules Hence, Net Energy Yield in Glycolysis =  2 ATP + 6 ATP = 8 ATP molecules

2 ATPs consumed 2X1 = 2 NADH produced 2X2 = 4 ATPs produced

Rate Limiting Step In chemical kinetics, the overall rate of a reaction is often approximately determined by the slowest step, known as the rate-determining step (RDS) or rate-limiting step. For a given reaction mechanism, the prediction of the corresponding rate equation (for comparison with the experimental rate law) is often simplified by using this approximation of the rate-determining step.

Regulatory Enzymes of Glycolysis The four regulatory enzymes are  hexokinase (or glucokinase in the liver),  phosphofructokinase, and  pyruvate kinase. 

Irreversible steps of Glycolysis conversion of glucose into glucose 6 phosphate, fructose 6 phosphate into fructose 1,6 bisphosphate , phosphoenolpruvate into pyruvic acid are irreversible i.e. step 1,3,10... 1 3 10

Thank You Nilansu Das Dept. of Molecular Biology Surendranath College