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IBMS SR > Glycogen Synthesis > Flashcards

Glycogen Synthesis Flashcards

1
Q

what are excess carbohydrates stored as when glycogen reserves are full

A

converted into fat for storage

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2
Q

what molecule is surplus glucose stored as

A

glycogen

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3
Q

what is the process of glycogenesis

A
  1. phosphorylation of glucose VIA GLUCOKINASE +/OR HEXOKINASE- using 1 molecule of ATP
  2. conversion of glucose 6 phosphate into glucose 1 phosphate by PHOSPHOGLUCOMUTASE (reversible step)
  3. glucose 1 phosphate is converted into uridine diphosphate. UDP glucose catalysed by UDP GLUCOSE PYROPHOSPHORYLASE
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4
Q

what must happen to glucose before it is added to the non reducing chain

A

it is phosphorylated

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5
Q

what is the equation for the hydrolysis of pyrophosphate

A

pyrophosphate + water—-> 2 free inorganic phosphates drives the phosphrylation of glucose reaction

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6
Q

what do we need to do to the phosphorylated glucose before it is added to the glycogen chain

A

it needs to be primed- and it is primed by glycogen with a minimum number of two units

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7
Q

what provides the energy to attach the new sugar to the non reducing end

A

high energy bond between the sugar and the nucleoside diphosphate

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8
Q

how’s the branching of the glycogen molecule completed

A

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

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9
Q

what conditions do we need to branch a glucose molecule off a chain

A

minimum long chain length of 10 glycol units and then 4 units minimum of the branching chain length

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10
Q

what is missing in Andersons disease

A

deficiency of chain branching enzyme (type IV glycogen storage disease),

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11
Q

how do we control the glycogen synthesis

A

hormones

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12
Q

which hormone is used to control glycogen synthesis

A

insulin

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13
Q

what is the pathway for glycogen synthesis

A
  1. insulin binds to the tyrosine kinase( insulin receptor)
  2. activates protein kinase using ATP
  3. activates phosphoprotein phosphatase 1
  4. prosphoprotein phosphatase 1 is activated by glucose then undergoes hydrolysis to activate glycogen synthase a
  5. this allows glycogen synthesis to occur
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14
Q

what hormone is secreted in response to increased blood glucose

A

insulin

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15
Q

where is insulin released from

A

it is released from the b cells in the islets of langerhans

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16
Q

which organs does insulin target

A

muscles
liver
apdipose

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17
Q

what does insulin do in the muscles

A

insulin increases the number of membrane glucose transporters and increases glucose uptake
also activates glycogen synthesis

18
Q

what does insulin do in the liver

A

no effect on the number of membrane glucose transporters

affects glycogen synthesis so can be stored as glucose

19
Q

how much glycogen can we store

A

around 300g of glycogen

20
Q

what happens to xs glucose when glycogen stores are full

A

it is stored as fat and sent to the adipose

21
Q

what does insulin do to the adipose

A

increases the number of membrane glucose transporters

also stimulates the conversion of glucose to fat for storage

22
Q

how many types of diabetes are there

A

two- type 1 and type 2

23
Q

describe type 1 diabetes

A

juvenile diabetes
insulin dependant diabetes
b cell destruction and there is a deficiency of insulin production

24
Q

how do we treat type 1 diabetes

A

insulin injection

25
Q

describe type 2 diabetes

A

non insulin dependant diabetes

risk factors- obesity and genetic factors

26
Q

how do we treat type 2 diabetes

A

diet
exercise
hypoglycaemic drugs and sometimes insulin

27
Q

what happens in uncontrolled diabetes

A

elevated blood glucose causes salivary concentrations to increase and this can lead to oral disease esp periodontitis

28
Q

what is gluconeogensis

A

synthesis of new glucose from non carbohydrate sources

29
Q

where does gluconeogensis take place

A

in the liver and slightly the kidneys

30
Q

what are the precursors of gluconeogenesis

A

lactate
glycerol
AA

31
Q

what are the stages of gluconeogenesis

A
  1. pyruvate is actively transported into the mitochondria using ATP AND converted into oxaloacetate via PYRUVATE CARBOXYLASE
  2. oxalocacte is converted into malate via MALATE DEHYDROGENASE which also reduces NAD
  3. Malate can use transporters to get out of the mitochondria
  4. Malate is then converted BACK TO OXALOACETATE VIA MALATE dehydrogenase also producing NADH
  5. oxaloacteetae is converted into PHOSPHOENOLPYRUVATE VIA PHOSPHOENOLYPYRUVATE CARBOXYKINASE and converts GTP into GDP+CO2
  6. 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
32
Q

what do the enzymes in gluconeogenesis require

A

Magnesium

33
Q

what prevents pyruvate kinase from working

A

glucagon- in turn stops the futile cycle of just the resynthesis of pyruvate

34
Q

what is the next stage of gluconeogenesis

A

fructose 1,6 phosphate to fructose 6 phosphate by FRUCTOSE 1,6 BISPHOSPHATASE - driven by hydrolysis

35
Q

what does fructose 1,6 bisphosphatase need

A

magnesium

36
Q

what is the third stage of gluconeogenesis

A

glucose 6 phosphate into glucose by glucose 6 phosphatase

37
Q

what happens during fasting to glycerol

A

our fat stores are broken down to release fatty acids and glycerol

38
Q

what is the pathway for glycerol as a glucose precursor

A

glycerol is converted into glycerol phosphate via glycerol kinase and then into DHAP by glycerol phosphate dehydrogenase

39
Q

what can happen to lactate

A

it can be oxidised into pyruvate by lactate dehydrogenase and in turn reduces NAD

40
Q

what happens after lactate is converted into pyruvate

A

it is converted into oxaloacetate by pyruvate carboxylase and then oxaloacetate is converted into phosphoenolpyruvate via mitochondrial PEP carboxylase

41
Q

where does the energy for gluconeogenesis come from

A

fat( beta oxidation of fatty acids)

muscle protein degradation to amino acids( C skeleton can be oxide for energy)

42
Q

how many high energy phosphate groups do we use for gluconeogenesis

A

6( 4ATP+ 2GTP)

IBMS SR (38 decks)

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