Energy Storage Flashcards
which cells have an absolute requirement for glucose
RBCs, lens of the eye, medulla of the kidney and neutrophils
at what glucose plasma level does death and brain damage result from
0.6 mmol/L
what can be used in blood tests to determine plasma glucose levels
HbA1c
what is glucose stored as
glycogen
what does muscle glycogen supply
glucose to skeletal muscle cells
what does liver glycogen supply
glucose to the body
describe the structure of glycogen
there is a central protein glycogenin with glucose residues branching off linked by alpha-1,4 and alpha-1,6 glyosidic bonds
what is glycogenesis
to production of glycogen
outline glycogenesis
- glucose and ATP are converted into G6P and ADP by hexokinase
- G6P is converted into G1P by phosphoglucomutase
- G1P, UTP and H20 are converted into UDP-glucose by G1P uridylyltransferase
- UDP-glucose reacts with glycogen to add the glucose residue onto the glycogen molecule
which 2 enzymes can add the glucose residue from the UDP-glucose onto the glycogen molecule
- glycogen synthase for alpha-1,4 bonds
- branching enzyme for alpha-1,6 bonds
what is glycogenolysis
breakdown of glycogen
outline glycogenolysis
- G1P is released from the glycogen by glycogen phosphorylase or de-branching enzyme
- G1P is converted into G6P by phosphoglucomutase
true or false: glycogenolysis is the reversal of glycogenesis
false - different enzymes allow inhibition and stimulation of the different pathways
what happens to the G6P produced by liver cells
converted into glucose and released into the blood for use by other tissues
what happens to the G6P produced by muscle cells
used by muscle cells in glycolysis for energy production
what enzyme in the liver converts G6P into glucose
glucose-6-phosphatase
what is the rate limiting enzyme in glycogen synthesis
glycogen synthase
what is the rate limiting enzyme in glycogen degradation
glycogen phosphorylase
what hormone increases the activity of glycogen synthase
insulin
what hormone increases the activity of glycogen phosphorylase
glucagon
true or false: AMP is an allosteric activator of glycogen phosphorylase
true - but only in the muscles not in the liver
give 2 examples of glycogen storage diseases
- von Gierke’s disease
2. McArdle disease
what is von Gierke’s disease
deficiency in glucose 6 phosphatase
what is McArdle disease
deficiency in muscle glycogen phosphorylase
what is gluconeogenesis
production of glucose
what are the 3 major precursors of glucose
- lactate
- glycerol
- amino acids
where does gluconeogenesis occur
liver (and also the kidney)
in what cycle is lactate used in respiration
cori cycle
outline the cori cycle
glucose is converted into lactate in muscle which then travels in the blood to the liver where its converted back to glucose
what are the 3 key enzymes in gluconeogensis
- glucose-6-phosphatase
- fructose 1,6-bisphosphatase
- PEPCK
what does glucose-6-phosphatase do
converts G6P into glucose
what does fructose-1,6-bisphosphatase do
converts fructose 1,6-bisphosphate into G6P
what does PEPCK do
converts oxaloacetate into phosphoenolpyruvate
which hormone stimulates gluconeogensis
glucagon and cortisol
which hormone inhibits gluconeogenesis
insulin
what are lipids stored as
triacylglycerides
where are triacylglycerides stored
in adipose tissue
when are triacylglycerides used for energy
in prolonged exercise, pregnancy, stress and starvation
what enzyme breaks down triacylglycerides
pancreatic lipases
what are triacylglycerides broken down into
fatty acids and glycerol
what happens to the fatty acids and glycerol in intestinal epithelia cells
they are reformed to TAGs then converted into chylomicrons where the enter the lymph system
where do the chylomicrons drain into the blood
left subclavian vein
what hormone mobilised TGA metabolism
glucagon and adrenaline
what hormone inhibits the metabolism of TGAs
insulin
what happens to the TGAs in the blood
they can either be stored in adipose tissue or used in fatty acid oxidation
what is lipogenesis
fatty acid synthesis
where does lipogenesis occur
liver
outline lipogenesis
- pyruvate is produced from glucose in the cytoplasm
- pyruvate enters the mitochondria and is converted into citrate
- citrate moves into the cytoplasm and is cleaved into acetyl CoA and oxaloactetate
- acetyl CoA is converted into malonyl CoA
- malonyl CoA is used to build fatty acids
what enzyme converts Acetyl CoA into malonyl CoA
Acetyl-CoA carboxylase
what enzyme complex uses malonyl CoA to produce fatty acids
fatty acid synthase complex
where does fatty acid synthesis occur
cytoplasm
true or false; only small amounts of energy are required in lipogenesis
false
what enzyme regulates lipogenesis
acetyl-CoA carboxylase
what hormone stimulates lipogenesis
insulin
