Glycogen is a polysaccharides which is formed from monosaccharide called glucose. when we intake a lot of glucose, some of it is used in respiration whereas the remaining is stored in liver in glycogen form. as the body need glucose whose lower level is detected by master gland in blood. then glycogen in liver is releaed again and converted nback to glucose. it reach to every cell inside mitochondria where respiration occur and glucose undergo glycolysis, kreb cycel and electron transport chain to produce ATP.