Glycogen

• What is the storage form of glucose in animals?

  Glycogen
• Where is glycogen mainly found in humans?

  Liver and muscles
• What type of bonds link glucosyl units in glycogen?

  α-1,4 glycosidic bonds

  
• How often do α-1,6 branches occur in glycogen?

  Every 8 to 10 glucosyl units
• What are the main functions of glycogen in the body?

  • Immediate energy source during muscle contraction
  • Maintains blood glucose levels during fasting
  • Important for regulation of blood glucose
  • Fuel for anaerobic activity during high-intensity exercise

  
• How does glycogen in muscles contribute during physical activity?

  Provides glucose-6-phosphate for glycolysis

  
• What role does glycogen in the liver play during fasting?

  Releases glucose into the bloodstream
• What is the role of glycogen in maintaining normoglycemia?

  Prevents hypoglycemia during fasting
• What can dysfunction in glycogen metabolism lead to?

  Severe hypoglycemia or hyperglycemia
• What is the primary anaerobic fuel source during high-intensity exercise?

  Muscle glycogen
• What are the main steps in glycogenesis?

  1. Phosphorylation of glucose to glucose 6-phosphate
  2. Formation of UDP-glucose and transfer of glucosyl units
  3. Creation of α(1,6) branches by branching enzyme

  
• What is the first step in glycogenesis?

  Phosphorylation of glucose to glucose 6-phosphate

  
• What enzyme transfers glucosyl units during glycogenesis?

  Glycogen synthase

  
• What does the branching enzyme do in glycogenesis?

  Creates α(1,6) linkages

  
• What is the process of glycogenolysis?

  • Pathway for glycogen degradation
  • Glycogen phosphorylase removes glucosyl units
  • Debranching enzyme hydrolyzes branching points

  
• What enzyme removes glucosyl units during glycogenolysis?

  Glycogen phosphorylase

  
• What is produced when glycogen phosphorylase acts on glycogen?

  Glucose-1-phosphate

  
• What is the role of the debranching enzyme in glycogenolysis?

  Removes glucosyl residues near branch points

  
• What does phosphoglucomutase do in glycogenolysis?

  Converts glucose-1-phosphate to glucose-6-phosphate

  
• What is the function of hepatic glucose-6-phosphatase?

  Hydrolyzes glucose-6-phosphate to glucose

  
• Why can't muscle release glucose into the bloodstream?

  Muscle lacks glucose-6-phosphatase
• What regulates glycogen synthesis and degradation in the liver?

  • Insulin/glucagon ratio
  • Blood glucose levels
  • Activated by epinephrine during exercise

  
• What stimulates glycogenolysis in skeletal muscles?

  Increase in AMP concentration

  
• What role does calcium play in muscle glycogenolysis?

  Stimulates glycogen breakdown during contraction

  
• How does epinephrine affect glycogenolysis?

  Stimulates glycogen breakdown during stress
• What is the key enzyme for glycogenolysis?

  Glycogen phosphorylase

  
• How does glycogen synthase activity change with adrenaline?

  Decreased by adrenaline
• How does insulin affect glycogen synthase activity?

  Enhances glycogen synthase activity
• What are the key regulatory factors for glycogen metabolism in muscles?

  • Glycogen phosphorylase activated by glucagon and adrenaline
  • Glycogen stores decrease little during fasting
  • Glycogen synthase activity regulated by insulin and adrenaline