Leyland 9 Fuel Storage - Glycogen Flashcards
catabolic
- breakdown of complex molecules to produce energy
Fuel → CO2 + H2O + useful products - Usually oxidative
anabolic
- formation of complex molecules from simple ones, utilising energy
energy + simple precursors → complex molecules
What happens to food fuel supplies that exceed immediate needs?
Carbohydrates -> stored as glycogen
Lipids -> stored as TAGs
Proteins -> not stored
Type of fuels
x3
- Lipids (triacylglycerol) - largest energy store
- Glycogen - vital for glucose requiring tissues
- Muscle protein- important in prolonged starvation
Glucose requirements of tissues.
- All tissues: metabolise glucose
- Blood [glucose] regulated (~5mM).
- some absolute requirement & uptake by these tissues depends on [blood]
- CNS (brain) prefers glucose
- fructose/galactose mainly -metabolised in the liver
Which tissues have glucose requirements?
(rbc, wbc, kidney medulla, lens of the eye)
CNS (brain) prefers glucose
Glycogen:
– a1-4 and a1-6 glycosidic bonds
- highly branched
• High molecular weight polymers 10^7 - 10^8
• No specialised storage tissue (stored in granules in muscle & liver)
Glycogen is used differently in
muscle and liver
Glycogen in Muscle
Glycogen -> glucose 1P -> Glucose 6P -> glycolysis => ATP +lactate + CO2
Glycogen in Liver
Glycogen -> glucose 1P -> glucose 6P -> glucos-6-phosphate -> blood glucose
<- Gluconeogenesis
Glycogen synthesis:
Enzyme:
Function:
glycogen synthase (GS):
- +’s glucosyl residues from UDP-glucose
- catalyses a-1, 4 linkages
• ~ 7 residues transferred and joined via a-1, 6 linkages by a branching enzyme
Glycogen breakdown:
Enymes:
Function:
- glycogen phosphorylase: -‘s glucose 1-phosphate units
- Glycogen phosphorylase: only break a-1, 4 linkages
- ~3 residues transferred onto another branch by transferase
- Glucosidase breaks a-1, 6 linkages
Reciprocal regulation of glycogen synthesis and breakdown:
glucagon/adrenaline:
synthase down
phosphorylase up
insulin:
synthase up
phosphorylase down
