Glycogen Synthesis Flashcards
what are excess carbohydrates stored as when glycogen reserves are full
converted into fat for storage
what molecule is surplus glucose stored as
glycogen
what is the process of glycogenesis
- phosphorylation of glucose VIA GLUCOKINASE +/OR HEXOKINASE- using 1 molecule of ATP
- conversion of glucose 6 phosphate into glucose 1 phosphate by PHOSPHOGLUCOMUTASE (reversible step)
- glucose 1 phosphate is converted into uridine diphosphate. UDP glucose catalysed by UDP GLUCOSE PYROPHOSPHORYLASE
what must happen to glucose before it is added to the non reducing chain
it is phosphorylated
what is the equation for the hydrolysis of pyrophosphate
pyrophosphate + water—-> 2 free inorganic phosphates drives the phosphrylation of glucose reaction
what do we need to do to the phosphorylated glucose before it is added to the glycogen chain
it needs to be primed- and it is primed by glycogen with a minimum number of two units
what provides the energy to attach the new sugar to the non reducing end
high energy bond between the sugar and the nucleoside diphosphate
how’s the branching of the glycogen molecule completed
by transferring a minimum of 6 alpha 1-4 glucan units from the elongated chain onto the same or neighbouring chain by forming a 1,6 linkage via CHAIN BRANCHING ENZYME
what conditions do we need to branch a glucose molecule off a chain
minimum long chain length of 10 glycol units and then 4 units minimum of the branching chain length
what is missing in Andersons disease
deficiency of chain branching enzyme (type IV glycogen storage disease),
how do we control the glycogen synthesis
hormones
which hormone is used to control glycogen synthesis
insulin
what is the pathway for glycogen synthesis
- insulin binds to the tyrosine kinase( insulin receptor)
- activates protein kinase using ATP
- activates phosphoprotein phosphatase 1
- prosphoprotein phosphatase 1 is activated by glucose then undergoes hydrolysis to activate glycogen synthase a
- this allows glycogen synthesis to occur
what hormone is secreted in response to increased blood glucose
insulin
where is insulin released from
it is released from the b cells in the islets of langerhans
which organs does insulin target
muscles
liver
apdipose
what does insulin do in the muscles
insulin increases the number of membrane glucose transporters and increases glucose uptake
also activates glycogen synthesis
what does insulin do in the liver
no effect on the number of membrane glucose transporters
affects glycogen synthesis so can be stored as glucose
how much glycogen can we store
around 300g of glycogen
what happens to xs glucose when glycogen stores are full
it is stored as fat and sent to the adipose
what does insulin do to the adipose
increases the number of membrane glucose transporters
also stimulates the conversion of glucose to fat for storage
how many types of diabetes are there
two- type 1 and type 2
describe type 1 diabetes
juvenile diabetes
insulin dependant diabetes
b cell destruction and there is a deficiency of insulin production
how do we treat type 1 diabetes
insulin injection
describe type 2 diabetes
non insulin dependant diabetes
risk factors- obesity and genetic factors
how do we treat type 2 diabetes
diet
exercise
hypoglycaemic drugs and sometimes insulin
what happens in uncontrolled diabetes
elevated blood glucose causes salivary concentrations to increase and this can lead to oral disease esp periodontitis
what is gluconeogensis
synthesis of new glucose from non carbohydrate sources
where does gluconeogensis take place
in the liver and slightly the kidneys
what are the precursors of gluconeogenesis
lactate
glycerol
AA
what are the stages of gluconeogenesis
- pyruvate is actively transported into the mitochondria using ATP AND converted into oxaloacetate via PYRUVATE CARBOXYLASE
- oxalocacte is converted into malate via MALATE DEHYDROGENASE which also reduces NAD
- Malate can use transporters to get out of the mitochondria
- Malate is then converted BACK TO OXALOACETATE VIA MALATE dehydrogenase also producing NADH
- oxaloacteetae is converted into PHOSPHOENOLPYRUVATE VIA PHOSPHOENOLYPYRUVATE CARBOXYKINASE and converts GTP into GDP+CO2
- at this point it can continue the gluconeogenesis pathway or it can be converted into pyruvate again by pyruvate kinase ( do not want this to happen)
7 glucagon prevents pyruvate kinase from working
what do the enzymes in gluconeogenesis require
Magnesium
what prevents pyruvate kinase from working
glucagon- in turn stops the futile cycle of just the resynthesis of pyruvate
what is the next stage of gluconeogenesis
fructose 1,6 phosphate to fructose 6 phosphate by FRUCTOSE 1,6 BISPHOSPHATASE - driven by hydrolysis
what does fructose 1,6 bisphosphatase need
magnesium
what is the third stage of gluconeogenesis
glucose 6 phosphate into glucose by glucose 6 phosphatase
what happens during fasting to glycerol
our fat stores are broken down to release fatty acids and glycerol
what is the pathway for glycerol as a glucose precursor
glycerol is converted into glycerol phosphate via glycerol kinase and then into DHAP by glycerol phosphate dehydrogenase
what can happen to lactate
it can be oxidised into pyruvate by lactate dehydrogenase and in turn reduces NAD
what happens after lactate is converted into pyruvate
it is converted into oxaloacetate by pyruvate carboxylase and then oxaloacetate is converted into phosphoenolpyruvate via mitochondrial PEP carboxylase
where does the energy for gluconeogenesis come from
fat( beta oxidation of fatty acids)
muscle protein degradation to amino acids( C skeleton can be oxide for energy)
how many high energy phosphate groups do we use for gluconeogenesis
6( 4ATP+ 2GTP)
