Glycogen tissue stores

A. After a meal of carbohydrates, glycogen is stored in the liver and in muscle, and triacyl-glycerols are stored in adipose tissue. The level of glucagon in the blood decreases, and gluconeogenesis decreases. The brain oxidizes glucose to C02 and EL20 while the red blood cells produce lactate. 

Glycogen is an energy reserve in animals, just as starch is in plants. Glycogen is similar in structure to amylopectin, but in a glycogen molecule a branch is found every 12 glucose units. Glycogen is stored in the liver and skeletal muscle tissues. 

What would happen to a 70-kg man if the 135,000 kcal stored as triacylglycerols in his 18 kg of adipose tissue were stored instead as skeletal muscle glycogen It would take approximately 34 kg glycogen to store as many calories. Glycogen, because it is a polar molecule with -OH groups, binds approximately 4 times its weight in water, or 136 kg. Thus, his fuel stores would weigh 170 kg. 

The glucose from the intestine that is not metabolized by the liver travels in the blood to peripheral tissues (most other tissues), where it can be oxidized for energy. Glucose is the one fuel that can be used by all tissues. Many tissues store small amounts of glucose as glycogen. Muscle has relatively large glycogen stores. 

Severe depletion of glycogen often results in a rebound effect, in which so much is made that some is stored in inappropriate tissues, including the heart, and mineral imbalances often occur. It is best to exercise moderately before the glycogen loading because then the glycogen is stored more effectively and safely in the liver and muscle tissue where it is most needed. 

Insulin appears to activate a process that helps glucose molecules enter the cells of striated muscle and adipose tissue Figure 49-1 depicts normal glucose metabolism. Insulin also stimulates die synthesis of glycogen by die liver. In addition, insulin promotes protein syntiiesis and helps the body store fat by preventing its breakdown for energy. 

Notes Assuming a moderately active 70 kg man with 40% of body weight as muscle (28 kg), a liver weight of 1.8 kg, a plasma volume of 3 L, and 9 kg of adipose tissue. Endurance trained individuals store -125-150 mmol/kg wet muscle of glycogen in muscle and 400-700 mmol/kg wet tissue of glycogen in liver,... 

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