The process of breaking down glucose step by step is called glycolysis. Glycolysis occurs in the cytoplasm of the cell and consists of ten steps. The first step is the phosphorylation of glucose to form glucose-6-phosphate. This step is catalyzed by the enzyme hexokinase. Glucose-6-phosphate is then isomerized to form fructose-6-phosphate. This step is catalyzed by the enzyme phosphoglucomutase.
Fructose-6-phosphate is then phosphorylated to form fructose-1,6-bisphosphate. This step is catalyzed by the enzyme phosphofructokinase-1. Fructose-1,6-bisphosphate is then cleaved into two three-carbon molecules, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. This step is catalyzed by the enzyme aldolase.
Glyceraldehyde-3-phosphate is then oxidized to form 1,3-bisphosphoglycerate. This step is catalyzed by the enzyme glyceraldehyde-3-phosphate dehydrogenase. 1,3-Bisphosphoglycerate is then phosphorylated to form 3-phosphoglycerate. This step is catalyzed by the enzyme phosphoglycerate kinase.
3-Phosphoglycerate is then isomerized to form 2-phosphoglycerate. This step is catalyzed by the enzyme phosphoglycerate mutase. 2-Phosphoglycerate is then dehydrated to form phosphoenolpyruvate. This step is catalyzed by the enzyme enolase.
Phosphoenolpyruvate is then transferred to ADP to form ATP and pyruvate. This step is catalyzed by the enzyme pyruvate kinase. Pyruvate can then enter the citric acid cycle, where it is further oxidized to produce ATP, CO2, and H2O.
The step-by-step breakdown of glucose is necessary for the body to efficiently extract energy from glucose. If glucose were broken down all at once, the cell would be overwhelmed with energy and unable to use it all. By breaking down glucose step by step, the cell can carefully regulate its energy production and produce ATP as needed.
