Energy Storage Flashcards
List a few cells that are glucose-dependant
- RBCs
- Neutrophils
- Kidney medulla cells
- Lens of the eye
What is glycogen?
Glucose stores in the form of granules in muscle and liver
Describe the structure of glycogen
- Chains of glucose residues that is highly branched (through alpha 1-6 glycosidic bonds)
- Attached to glycogenin (protein dimer) at the centre
Outline the steps of glycogenesis
1) glucose —> glucose 6-phosphate
(Hexokinase or glucokinase in the liver)
2) glucose 6-phosphate -> glucose 1-phosphate
(Phosphoglucomutase)
3) glucose 1-phosphate + H2O —> UDP-glucose
(G1P uridylyl transferase)
4) UDP-glucose + glycogen (n residue) —> glycogen (n+1) + UDP
(Glycogen synthase for alpha 1-4
Branching enzyme for alpha 1-6)
Outline the process of glycogenolysis
1)Glycogen + Pi —> glucose 1-phosphate + glycogen (n-1)
(Glycogen phosphorylase or debranching enzyme)
2) glucose 1-phosphate —> glucose 6-phosphate
(Phosphoglucomutase)
Compare the uses of glycogen in muscle and liver
Liver = blood glucose buffer Muscle = energy production (no glucose 6-phosphatase)
List the hormones involved in regulation of liver glycogen and what their effect is
Glucagon/adrenaline = phosphorylates glycogen synthase or phosphorylase to decrease and increase enzyme activity respectively
Insulin = dephosphorylates glycogen synthase or phosphorylase to increase and decrease enzyme activity respectively
Define what Gluconeogenesis is and list the major precursors
Gluconeogenesis is the production of new glucose mainly in the liver but can also occur in kidney cortex. Major precursors: -lactate -glycerol -amino acids
Why can’t acetyl~CoA can’t be converted to pyruvate?
Pyruvate dehydrogenase reaction is irreversible
What are the three key enzymes in Gluconeogenesis?
1) Phosphoenolpyruvate carboxykinase (PEPCK)
- oxaloacetate (from pyruvate) to phosphoenolpyruvate
2) Fructose 1-6 bisphosphatase
3) Glucose 6-phosphatase
Which hormones regulate gluconeogensis and what are their corresponding effects?
Glucagon/cortisol = stimulate
-by increasing amount of key enzymes
Insulin = inhibit
-by decreasing amount of key enzymes
What is the main lipid molecule used as storage?
Triacylglycerols
Where are triacylglycerols stored?
Adipocytes in adipose tissue
What is lipogenesis?
Fatty acid synthesis
Briefly describe the process of lipogenesis
1) Glucose to pyruvate (glycolysis in the cytoplasm)
2) Pyruvate enters mitochondria
3) Pyruvate to Citrate (by adding OAA and acetyl~Coa)
4) Citrate leaves mitochondria and gets cleaved releasing OAA and acetyl~CoA
5) Acetyl~CoA turned to malonyl~CoA by acetyl~CoA carboxylase
6) Malonyl ~CoA turned into fatty acids by fatty acid synthase complex
