The phosphorylation adds a charged phosphate group so the glucose 6-phosphate cannot easily cross the cell membrane.

[1] This irreversible reaction is the initial step of the pentose phosphate pathway, which generates the useful cofactor NADPH as well as ribulose-5-phosphate, a carbon source for the synthesis of other molecules.

[1] Also, if the body needs nucleotide precursors of DNA for growth and synthesis, G6P will also be dehydrogenated and enter the pentose phosphate pathway.

On the other hand, glycogen synthase is inhibited when it is phosphorylated by protein kinase during times of high stress or low levels of blood glucose, via hormone induction by glucagon or adrenaline.

This free glucose can pass through membranes and can enter the bloodstream to travel to other places in the body.

The catalytic site is found on the lumenal face of the membrane, and removes the phosphate group from glucose 6-phosphate produced during glycogenolysis or gluconeogenesis.

Free glucose is transported out of the endoplasmic reticulum via GLUT7 and released into the bloodstream via GLUT2 for uptake by other cells.

Muscle cells lack this enzyme, so myofibers use glucose 6-phosphate in their own metabolic pathways such as glycolysis.

Importantly, this prevents myocytes from releasing glycogen stores they have obtained into the blood.