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MEH > Energy storage > Flashcards

Energy storage Flashcards

1
Q

what are the main forms of energy storage

A

glycogen and fat

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2
Q

where is glycogen stored

A
  • muscle
  • liver
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3
Q

how is glycogen stored in the liver

A

granules

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4
Q

how much glycogen does the liver contain

A

100g

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5
Q

how much glycogen do muscles contain

A

300g

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6
Q

what is the difference in glycogen in liver and muscle

A
  • in liver glycogen mobilised to buffer plasma glucose levels so transported to blood
  • in muscle glycogen only used for muscle
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7
Q

what is advantage of storing glycogen as granules

A

minimal osmotic effect

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8
Q

describe the structure of glycogen

A
  • polymer of glucose residues
  • starts from dimer glycogenin
    -residues linked by a-1,4 glycosidic bonds and branch points from a-1,6 glycosidic bonds
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9
Q

how often is a branch formed on glycogen

A

every 8-10 residues

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10
Q

what is glycogenesis

A

glycogen synthesis

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11
Q

what is the first step and enzyme of glycogenesis

A

glucose+ATP –> glucose-6-phosphate +ADP

enzyme: hexokinase/ glucokinase in liver

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12
Q

what is the second step and enzyme of glycogenesis

A

glucose-6-phosphate –> glucose-1-phosphate

enzyme: phosphoglucomutase

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13
Q

what is the third step and enzyme of glycogenesis

A

G1P +UTP +H2O– > UDP-glucose + Pi

enzyme: G1P uridlyltransferase

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14
Q

what is the final step in glycogenesis and what enzymes are required

A

glycogen (n residues) + UDP- glucose –> glycogen (n+1 residues) + UDP

  • enzymes:
    -1-4: glycogen synthase
    -1-6: branching enzyme
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15
Q

what is glycogenolysis

A

glycogen degradation

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16
Q

what is the first step and enzymes in glycogenolysis

A

glycogen (n residues ) + Pi –> G1P + glycogen (n-1)

enzymes:
1-4: glycogen phosphorylase
1-6: de-branching enzyme

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17
Q

what is the second step and enzyme of glycogenolysis

A

G1P –> G6P

enzyme:
phosphoglucomutase

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18
Q

why is glycogenolysis not a reversal of glycogenesis

A

uses diff enzymes

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19
Q

what is the fate of G6P from glycogenolysis

A
  • liver to turned to glucose by enzyme glucose-6-phosphotase transported to blood
  • muscle G6P used for glycolysis
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20
Q

why can glycogen in muscle not be used to buffer blood plasma glucose but liver glycogen can

A

muscle lacks enzyme glucose-6-phosphotase so cannot convert G6P to glucose so cannot cross mem

  • in liver G6P converted to glucose by glucose-6-phosphotase and glucose uses GLUT to transport to blood
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21
Q

what the rate limiting enzyme in glycogenesis

A

glycogen synthase

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22
Q

what is the rate limiting enzyme in glucogenolysis

A

glycogen phosphorylase

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23
Q

how does glucagaon and adrenaline affect glycogen synthase activity

A

decreases activity

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24
Q

how does glucagaon and adrenaline affect glycogen phosphorylase activity

A

increases

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25
Q

how does insulin affect glycogen synthase activity

A

increases

26
Q

how does insulin affect glycogen phosporylase activity

A

decreases

27
Q

give two examples of glycogen storage diseases

A

von Gierke’s disease (glucose-6-phosphotase deficiency)

McArdle disease (muscle glycogen phosphorylase deficiency)

28
Q

what is gluconeogenesis

A

production of new glucose

29
Q

when does gluconeogenesis occur

A

after 8 hours of fasting
liver glycogen stores start to deplete

30
Q

where does gluconeogenesis occur

A

liver
to some extent the kidney medulla

31
Q

what are the three precursors for gluconeogenesis

A
  • lactate (Cori cycle)
  • glycerol
  • amino acids
32
Q

why can acetyl CoA not be used for gluconeogenesis

A

pyruvate dehydrogenase reaction is irreversible so cannot be converted to pyruvate

33
Q

what does the enzyme PEPCK do

A

converts oxaloacetate to phospholpyruvate

34
Q

what are glucogenic amino acids converted to for gluconeogenesis

A

pyruvate or oxaloacetate

35
Q

what is lactate converted to for gluconeogenesis

A

pyruvate

36
Q

what is glycerol converted to for gluconeogenesis

A

dihydroxyacetone to fructose 1,6- bisphosphate

37
Q

what are the three enzymes in gluconeogenesis

A
  • PEPCK
  • fructose-1,6-bisphosphoatase
  • glucose-6-phosphatase
38
Q

what are the two regulation enzymes in gluconeogenesis

A
  • PEPCK
  • fructose-1,6-bisphophatase
39
Q

what is the effect of glucagon and cortisol on PEPCK and F16P activity

A

increases

40
Q

what is the effect of insulin on PEPCK and F16P activity

A

decreases

41
Q

what is an adipocyte

A

large lipid droplet mainly containing TAG and cholesterol ester

42
Q

what adaptation of adipocyte allows it to hold alot of fats

A

can expand as more fat added

43
Q

how many times can adipocytes increase in size before a new cell is made

A

4

44
Q

where does lipogenesis occur

A

liver

45
Q

what is lipogenesis

A

lipid synthesis

46
Q

why are triacylglycerols a good storage molecule

A
  • anhydrous
  • energy content per gram twice that or carbs or proteins
47
Q

what is the first step of lipogenesis

A
  • citrate from TCA cycle leaves mitochondria as ACoA cannot be transported out mito (oxaloacetate +acetyl CoA) cleaved back into OAA and ACoA
48
Q

what is the second step of lipogenesis for acetyl CoA

A
  • acetyl CoA converted to Malonyl CoA by enzyme : acetyl CoA carboxylase using ATP
49
Q

what is the second step of lipogenesis for oxaloacetate

A

converted to malate which is then converted to pyruvate by malic enzyme

50
Q

what happens to malonyl CoA in lipogenesis

A

goes to fatty acid synthase complex with NADPH from PPP and formation of pyruvate from malate which makes the fatty acids which combines with glycerol-3-p to make TAG which are then pacakged to go elsewhere

51
Q

why is acetyl CoA converted to malonyl CoA

A

want to add 2C and but we loose one from CO2 so as malonyl is 3 C adds 2C after loss of CO2

52
Q

what is the regulatory enzyme in lipogenesis

A

acetyl-CoA carboxylase

53
Q

what is the effect. of insulin and citrate on acetyl CoA carboxylase activity

A

increases

54
Q

what is the effect. of glucagon/ adrenaline/ AMP on acetyl CoA carboxylase activity

A

decreases

55
Q

what is lipolysis

A

fat mobilisation

56
Q

what enzyme is involved in lipolysis

A

hormone sensitive lipase

57
Q

what does hormone sensitive lipase do

A

converts TAG stored in adipose tissue to glycerol and FA in blood

58
Q

how does glucagon affect hormone sensitive lipase

A

activates

59
Q

how does insulin affect hormone sensitive lipase

A

inhibits

60
Q

what type of energy storage differs between a health weight and overweight

A

TAGs

61
Q

what is the normal plasma glucose level

A

5mmol/L

62
Q

what is hypoglycaemia

A

low plasma glucose levels

MEH (12 decks)

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