Glycogen Metabolism Flashcards
Constant levels of ______ in blood are absolute requirement for glycogen metabolism
Glucose
What is the preferred energy source for the brain? And required for RBCs?
Glucose
Glucose is essential for exercising muscle
T/F
True
3 main ways the body obtained Glucose
Food/catabolism (diet)
Anabolism (GNG)
Storage (as glycogen)
Mechanism for storing a supply of glucose in a reap idly mobilizable form
Glycogen
What cells can contain glycogen?
(Virtually) any cell
Where are the main stores of glycogen found?
Skeletal
-for its own use of fuel
Liver
-to maintain blood glucose during early fasting
Correlation between glycogen storage and water storage?
Glycogen storage is associated with significant amounts of water storage, therefore your weight can vary significantly based on the amount of glycogen you have stored
When is glycogen degraded to glucose?
When there is an absence of a dietary source
Where is glycogen released from?
the liver, and the kidney as kidney glycogen
When is muscle glycogen degraded?
When the exercising muscle needs an energy source
As glycogen stores are depleted, but the body still needs energy, what happens?
GNG takes over to provide glucose
Glycogen structure
Branched chain polysaccharide
Alpha(1,4) linkage
After around 8-10 alpha(1,4) linkages, there is a branch containing alpha(1,6)linkage
discrete cytoplasmic granules (beta-particles)
Large molecules of glucose that are associated with the enzymes necessary for synthesis and degradation
Steps of Glycogenesis
- Synthesis of Uridine diphosphate glucose
- Synthesis of a primer to initiate glycogen synthesis
- Elongation of glycogen chains
- Formation of branches
Why are branches important in glycogen?
Because they increase the solubility and they increase the number of nonreducing ends that allow faster synthesis and degradation
What energy source is used in step one of Glycogenesis?
UTP, to create UDP-glucose
Creates 2 Pi’s as byproducts
In step 2 of Glycogenesis, UDP-glucose serves as a….
Primer, to elongate existing glycogen chains.
If no glycogen primers are available, what happens?
Glycogenin can serve as a primer.
How do the glycogen chains elongate in step 3 of Glycogenesis ?
Glycogen synthase transfers UDP-glucose to the non-reducing end of the primer
Rate-limiting enzyme
How are branches formed in step 4 of Glycogenesis?
The branching enzyme removed a chains of 6-8 glucosyl residues from the ends of the glycogen chain and attached is to a non-terminal glucosyl residue by alpha(1,6)bond
Steps of Glycogenolysis
- Shortening of chains
- Removal of branches
- Conversion of G-1-P to G-6-P
- Dephosporylation of G-6-P to glucose
Where is the dephosphorylation of G-6-P primarily expressed? Where else, to a lesser extent?
In the liver and the kidney cortex.
In the pancreatic Beta cells and intestinal mucosa.
What enzyme causes the degradation of glycogen in Lysosomes?
Lysosomal alpha-1,4-glucosidase
Only 1-3% of glycogen.
