L28 Glycogen metabolism Flashcards
Why not just store glucose?
- Renal loss
* Glucose is osmotically active (would affect osmotic pressure)
Glycogen is a:
a) highly branched monosaccharide
b) unbranched polysaccharide
c) highly branched homopolysaccharide
d) highly branched heteropolysaccharide
c) highly branched homopolysaccharide
Glycogen chains are linked by α-1,4-glycosidic bonds. Branches are linked by…
α-1,6-glycosidic bonds
The largest glycogen stores in the body are found in…
Muscle
The liver, by weight, is:
a) 10% glycogen
b) 2% glycogen
c) 6% glycogen
d) 20% glycogen
a) 10% glycogen
Fat stores energy more efficiently, but requires…
Oxygen
The creation of glycogen is known as…
Glycogenesis
The breakdown of glycogen stores for use is known as…
Glycogenolysis
Step 1 of glycogenesis is…
Diversion
In diversion, glucose-6-phosphate is diverted from…
Glycolysis
In diversion, G-6-P is converted to G-1-P by the enzyme…
Phosphoglucomutase
Step 2 of glycogenesis is…
Activation
In activation, G-1-P is converted to UDP-glucose by…
UDP-Glucose pyrophosphate (with the addition of Uridine triphosphate)
Step 3 of glycogenesis is…
Polymerisation
In polymerisation, UDP-glucose is converted to…
Glycogen by glycogen synthase (which removes UDP)
In polymerisation, glucose is added to the glycogen chain with a…
α-1,4-glycosidic bond
Step 4 of glycogenesis is…
Glycogen branching
In glycogen branching, branches are added by the enzyme…
Amylo-(1,4 →1,6)-transglycosylase
The size of glycogen is limited by the decreasing activity of…
Glycogenin (over distance)
Glycogenolysis starts with the…
Erosion of chains
Glycogen phosphorylase converts glycogen monomers back into…
G-1-P
Glycogen phosphorylase is stored…
With glycogen in an inactive form
Glycogen phosphorylase is regulated by (2)…
Allosteric and hormonal control
Glycogen phosphorylase in the liver is regulated by glucose levels. In the muscle it is regulated by the level of…
AMP vs ATP
Why can’t glycogen phosphorylase process chains shorter than 4 residues in length?
The active site is situated far back in the enzyme
Step 2 of glycogenolysis is…
Debranching
Debranching occurs via the enzymes (2)…
α-(1-4)-transglycosylase (transfers all but one of the branch to the main chain)
α-(1-6)-glucosidase (releases the glucose)
Step 3 of glycogenolysis is…
Recovery
In recovery, G-1-P generated from glycogen is converted into…
G-6-P
In glycogenolysis, phosphoglucomutase converts…
G-1-P to G-6-P
The reverse of its action in glycogenesis
Glycogen is synthesised and broken down by…
Two separate pathways
Glycogen storage diseases (GSDs) (4)…
- Type 0 (liver glycogen synthase deficiency)
- Type I (Von Gierke’s disease)
- Type III (Cori’s disease)
- Type IV (Andersen’s disease)
Type 0 GSD results in an…
Inability to synthesise glycogen and is thus incompatible with life ☠️
Type I GSD (Von Gierke’s disease) is a…
Glucose-6-phosphatase deficiency which sometimes results in death
Type III GSD (Cori’s disease) is an…
Amylo-1,6-glucosidase deficiency which causes enlarged liver and hypoglycemia
Type IV GSD (Andersen’s disease) results in a…
Lack of glycogen branching
