Which of the following does not cross the cell membrane

Glucose-6-phosphate  "Glucose-6-phosphate cannot diffuse out of muscle cells".             —Pankaj Naik Glucose-6-phosphate cannot diffuse out of the cell as such. First, it has to be converted to glucose by glucose-6-phosphatase which then diffuse out of the cells. This occurs in liver. Thus, glucose can be used by other tissues. Muscle cells does not contain glucose-6-phosphatase, glucose-6-phosphate cannot be converted to glucose and glucose-6-phosphate can only by utilized as a source of energy by only muscle itself.