The enzyme not present in the skeletal muscles :
Correct Answer: Glucose 6 phosphatase
Description: D i.e. Glucose -6 - phosphataseThe role of glycogen in liver is to provide free glucose for expo to maintain the blood glucose level; whereas in muscles the role of glycogen is to provide a source of glucose-6-PO4 for glycolysis (to supply ATP for muscle contraction).This difference of fate of glycogen in liver & muscle is d/t absence of glucose -6- phosphatase enzyme in muscleQ. Because of absence of this enzyme, which catalyzes the final step of glycogenolysis, glycogen in muscles can only be conveed upto glucose-6- phosphate. Hence muscle glycogenolysis does not contribute to blood glucose directlyQ. Instead, in muscle, this glucose -6-PO4 can not cross plasma membrane and enters glycolysis producing energy (3ATP) needed for muscle contraction. The gain of an extra (1) ATP is d/t bypass of 1st step of glycolysis which requires 1 ATP (If glycolysis stas from glucose only 2 ATPs are produced). Lactic acid produced d/t glycolysis crosses the plasma membrane & reaches liver to form glucose.In liver glucose -6. phosphate is transpoed by glucose- 6-phosphate translocase into endoplasmic reticulum, where it is conveed to glucose by glucose- 6- phosphatase (this enzyme is also used in last step of gluconeogenesis). The glucose moves out of ER to cytosol and then released by hepatocytes into blood to maintin blood glucose levels untilgluconeogenesis stas.
Category:
Biochemistry
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