BCM 252 – Study Unit 4
The Metabolism of Glycogen in Animals
Vertebrate animals require a ready fuel source for brain and muscle
• Glycogen: a polymeric storage form of glucose in animals that is found primarily
in muscle and liver
• Glycogen breakdown in muscle delivers glucose needed for muscle contraction
within seconds
• Glycogen stored in the liver provides a reservoir that maintains homeostasis of
blood glucose
Glycogen granules have many tiers of branched chains of D-glucose
• Glycogen -granules: cytosolic granules that vary in size, structure, and
subcellular location
➢ Appear as electron-dense particles
-Granules cluster to form -granules in the liver
• -granules: protein-rich granules composed of 20-40 clustered -granules
➢ Release glucose slower than -granules
➢ Visible in well-fed animals, but absent after a 24-hour fast
➢ Often associate with tubules of the smooth ER
, Structure of a Glycogen -Granule
• Glycogenin dimer: serves as a primer
• Tiers of glucose residues are in (1→4) linkage, with (1→6)-linked branches
➢ Provides many free non-reducing ends
➢ Useful for meeting short-term demands for energy by increasing glucose
supply quickly
The Metabolism of Glycogen in Animals
Vertebrate animals require a ready fuel source for brain and muscle
• Glycogen: a polymeric storage form of glucose in animals that is found primarily
in muscle and liver
• Glycogen breakdown in muscle delivers glucose needed for muscle contraction
within seconds
• Glycogen stored in the liver provides a reservoir that maintains homeostasis of
blood glucose
Glycogen granules have many tiers of branched chains of D-glucose
• Glycogen -granules: cytosolic granules that vary in size, structure, and
subcellular location
➢ Appear as electron-dense particles
-Granules cluster to form -granules in the liver
• -granules: protein-rich granules composed of 20-40 clustered -granules
➢ Release glucose slower than -granules
➢ Visible in well-fed animals, but absent after a 24-hour fast
➢ Often associate with tubules of the smooth ER
, Structure of a Glycogen -Granule
• Glycogenin dimer: serves as a primer
• Tiers of glucose residues are in (1→4) linkage, with (1→6)-linked branches
➢ Provides many free non-reducing ends
➢ Useful for meeting short-term demands for energy by increasing glucose
supply quickly
