AP BIOLOGY

Detailed explanation-1: -The first step in glycolysis is catalyzed by hexokinase, an enzyme with broad specificity that catalyzes the phosphorylation of six-carbon sugars. Hexokinase phosphorylates glucose using ATP as the source of the phosphate, producing glucose-6-phosphate, a more reactive form of glucose.

Detailed explanation-2: -Step 1: Glucose is phosphorylated by the enzyme hexokinase to form glucose 6-phosphate. Glucose gains energy by being phosphorylated at the expense of one ATP. Step 2: Glucose 6-phosphate is converted into its isomer, fructose 6-phosphate, by an isomerase enzyme.

Detailed explanation-3: -From glycogen Glucose 6-phosphate is also produced during glycogenolysis from glucose 1-phosphate, the first product of the breakdown of glycogen polymers.

Detailed explanation-4: -Phosphorylation of glucose serves two important purposes. First, the addition of a phosphate group to glucose effectively traps it in the cell, as G6P cannot diffuse across the lipid bilayer. Second, the reaction decreases the concentration of free glucose, favoring additional import of the molecule.

Detailed explanation-5: -Production of glucose-6-phosphate The major reason for the immediate phosphorylation of glucose is to prevent diffusion out of the cell. The phosphorylation adds a charged phosphate group so the glucose-6-phosphate cannot easily cross the cell membrane.