What is the first step of glycolysis?

The first step of glycolysis involves the conversion of glucose to glucose 6-phosphate. This step is catalyzed by the enzyme hexokinase (or glucokinase in the liver), which phosphorylates glucose using a molecule of ATP. This phosphorylation is crucial as it helps to trap glucose within the cell because glucose 6-phosphate cannot easily cross the cell membrane. This phosphorylation also prepares glucose for subsequent steps in the glycolytic pathway, where it will undergo further transformations to ultimately drive the production of energy in the form of ATP.

By converting glucose to glucose 6-phosphate, the cell effectively signals that glucose is being utilized in metabolic pathways, and this step commits glucose to the glycolytic pathway. The importance of this first step cannot be overstated, as it is a regulatory point and is subject to allosteric regulation by various metabolites and energy status of the cell, influencing overall glycolytic flux.