glycogen

Examples of glycogen in the following topics:

• Connecting Other Sugars to Glucose Metabolism

  • Sugars, such as galactose, fructose, and glycogen, are catabolized into new products in order to enter the glycolytic pathway.
  • Glycogen, a polymer of glucose, is an energy-storage molecule in animals.
  • When there is adequate ATP present, excess glucose is shunted into glycogen for storage.
  • Glycogen is made and stored in both the liver and muscles.
  • The glycogen is hydrolyzed into the glucose monomer, glucose-1-phosphate (G-1-P), if blood sugar levels drop.

• Cell Signaling and Cellular Metabolism

  • The first enzyme promotes the degradation of glycogen by activating intermediate glycogen phosphorylase kinase (GPK) that in turn activates glycogen phosphorylase (GP), which catabolizes glycogen into glucose.
  • (Recall that your body converts excess glucose to glycogen for short-term storage.
  • When energy is needed, glycogen is quickly reconverted to glucose. ) Phosphorylation of the second enzyme, glycogen synthase (GS), inhibits its ability to form glycogen from glucose.
  • In this manner, a muscle cell obtains a ready pool of glucose by activating its formation via glycogen degradation and by inhibiting the use of glucose to form glycogen, thus preventing a futile cycle of glycogen degradation and synthesis.

• Galactosemia and Glycogen Storage Disease

  • Glycogen storage disease (GSD, also glycogenosis and dextrinosis) is the result of defects in the processing of glycogen synthesis or breakdown within muscles, liver, and other cell types.
  • Overall, according to a study in British Columbia, approximately 2.3 children per 100,000 births (one in 43,000) have some form of glycogen storage disease.
  • There are 11 distinct diseases that are commonly considered to be glycogen storage diseases (some previously thought to be distinct have been reclassified).

• Absorptive State

  • During this sleep period, anabolic processes are busy building up stores of fats and glycogen that will be needed in the future to provide energy for the growing baby.
  • The glucose then travels to the blood or is converted to glycogen and fat (triglyceride) for energy storage.
  • The glycogen and fat will be stored in the liver and adipose tissue, respectively, as reserves for the post-absorptive state.
  • The remaining glucose is taken in for use by body cells or stored in skeletal muscle as glycogen.

• Food Energy and ATP

  • When the amount of ATP available is in excess of the body's requirements, the liver uses the excess ATP and excess glucose to produce molecules called glycogen (a polymeric form of glucose) that is stored in the liver and skeletal muscle cells.
  • When blood sugar drops, the liver releases glucose from stores of glycogen.
  • Skeletal muscle converts glycogen to glucose during intense exercise.
  • The process of converting glucose and excess ATP to glycogen and the storage of excess energy is an evolutionarily-important step in helping animals deal with mobility, food shortages, and famine.

• Insulin Secretion and Regulation of Glucagon

  • Glucose is stored in the liver in the form of the polysaccharide glycogen, which is a glucan.
  • Liver cells have glucagon receptors and when glucagon binds to the liver cells they convert glycogen into individual glucose molecules and release them into the bloodstream—this process is known as glycogenolysis.
  • It's main role is to promote the conversion of circulating glucose into glycogen via glycogenesis in the liver and muscle cells.

• Muscle Metabolism

  • The glucose for glycolysis can be provided by the blood supply, but is more often converted from glycogen in the muscle fibers.
  • If glycogen stores in the muscle fibers are expended, glucose can be created from fats and proteins.
  • Cellular respiration plays a key role in returning the muscles to normal after exercise, converting the excess pyruvate into ATP and regenerating the stores of ATP, phosphocreatine, and glycogen in the muscle that are required for more rapid contractions.

• Pancreas

  • As blood glucose levels decline, alpha cells release glucagon to raise the blood glucose levels by increasing rates of glycogen breakdown and glucose release by the liver.
  • When blood glucose levels rise, such as after a meal, beta cells release insulin to lower blood glucose levels by increasing the rate of glucose uptake in most body cells, and by increasing glycogen synthesis in skeletal muscles and the liver.

• Hormonal Regulation of Metabolism

  • It also stimulates the liver to convert glucose to glycogen, which is then stored by cells for later use.
  • Glucagon raises blood glucose levels, eliciting what is called a hyperglycemic effect, by stimulating the breakdown of glycogen to glucose in skeletal muscle cells and liver cells in a process called glycogenolysis.
  • As the levels of glucose in the blood rise, insulin stimulates the cells to take up more glucose and signals the liver to convert the excess glucose to glycogen, a form in which it can be stored for later use.
  • When the levels of glucose in the blood fall, glucagon responds by stimulating the breakdown of glycogen into glucose and signals the production of additional glucose from amino acids.

• Carbohydrate Molecules

  • Starch, glycogen, cellulose, and chitin are primary examples of polysaccharides.
  • Glycogen is the storage form of glucose in humans and other vertebrates.
  • Glycogen is the animal equivalent of starch and is a highly branched molecule usually stored in liver and muscle cells.
  • Whenever blood glucose levels decrease, glycogen is broken down to release glucose in a process known as glycogenolysis.