Glycogen Metabolism Flashcards
(12 cards)
State characteristics of glucose
- It is a major metabolic fuel source
- It is degraded via glycolysis to produce ATP
If glucose is in excess, what will it be stored as? State the reason
As high molecular mass glucan
- to protect themselves from potential fuel shortage
In plants, glucose storage is called
starch
In animals, glucose storage is called as
glycogen
There are two form of starch
Amylose and amylopectin
Why does the body has to use glycogen for energy?
- Muscles cannot mobilize fat as rapidly as they can glycogen
- The fatty acid residues of fat cannot metabolize anaerobically
- Animals cannot convert fatty acids to glucose, so fat metabolism alone cannot adequately maintain essential blood glucose level
Glycogen can be found in two major storage tissues, what are they? and state the reason
1) muscle
- if in need of ATP, glycogen is converted to G67P for entry into glycolysis
2) liver
- low blood glucose concentration triggers glycogen breakdown to G6P which is then hydrolyzed to glucose and released into the blood stream
Glycogen breakdown requires the action of 3 enzymes, list them.
1) Glycogen phosphorylase
2) Glycogen debranching enzyme
3) Phosphoglucomutase
What is the function of glycogen phosphorylase?
Catalyzes glycogen phosphorolysis (bond cleavage by the substitution of a phosphate group) to yield glucose-1-phosphate (G1P)
Glycogen phosphorylase is regulated by
1) Allosteric interactions (ATP, G6P and glucose, inhibitors, AMP activator)
2) Covalent modification (phosphorylated and dephosphorylated)
There are two forms of glycogen phosphorylase:
1) Active form
- the phosphorylated enzyme
2) Inactive form
- dephosphorylated enzyme
What is the essential cofactor for the glycogen phosphorylase enzyme reaction
Pyridoxal phosphate
- active form of vitamin B6
- plays a role as a coenzyme in a variety of enzymatic reactions
