Glycolysis PDF

# Bioenergetics ## Glycolysis **Glycolysis** is the process of breakdown of glucose or similar hexose sugar into two molecules of pyruvates through a series of enzymatic reactions releasing some energy (as ATP) and reduced coenzymes (as NADH). It occurs in the cytoplasm. It is completed in two pha...

# Bioenergetics ## Glycolysis **Glycolysis** is the process of breakdown of glucose or similar hexose sugar into two molecules of pyruvates through a series of enzymatic reactions releasing some energy (as ATP) and reduced coenzymes (as NADH). It occurs in the cytoplasm. It is completed in two phases i.e., preparatory phase and oxidative phase. **Preparatory phase** is an investment phase in which two ATPs are consumed. Its end products are two molecules of G3P. On the other hand **oxidative phase** is **pay off phase** in which not only ATPs are produced through substrate level phosphorylation but it also produces NADH which upon further oxidation in respiratory electron transport chain yields more ATPs. The whole glycolysis pathway takes place in the following sub steps: 1. **Phosphorylation:** When glucose reacts with ATP, a phosphate group from ATP is transferred to glucose. In this way glucose is phosphorylated to glucose-6-phosphate. 2. **Isomerization:** Glucose-6-phosphate is changed to its isomer fructose-6-phosphate. 3. **Phosphorylation:** When fructose-6-phosphate reacts with another ATP, it is phosphorylated to Fructose-1, 6-bisphosphate. 4. **Splitting:** Now fructose-1, 6-bisphosphate splits up to form one molecule each of 3-carbon compounds, glyceraldehyde 3-phosphate (G3P) and dihydroxyacetone 3-phosphate. 5. **Isomerization:** The dihydroxyacetone 3-phosphate is ultimately changed into its isomer the glyceraldehyde 3-phosphate (G3P). In this way preparatory phase is completed. Next phase of glycolysis is proceeded by two molecules G3P, therefore, the remaining reactions occur twice. 6. **Dehydrogenation and Phosphorylation**