Both the liver and muscle contain glycogen, yet, unlike liver, muscle is not capable of contributing glucose to the circulation because muscle:

Ans. A. Does not have the enzyme glucose-6-phosphataseThe liver has the enzyme glucose-6- phosphatase, but muscle does not. Consequently, muscle is incapable of releasing glucose from glucose 6- phosphate. Glucose undergoes reactions other than glycolysis. Both liver and muscle have glucose-1- phosphatase and glycogen phosphorylase enzymes. The synthesis of glucose, called gluconeogenesis, is carried out mostly in the liver and, to some extent, in the kidneys.