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Phase 1 - S2 Metabolism, Endocrinology, Haematology > Energy Storage > Flashcards

Energy Storage Flashcards

1
Q

which cells have an absolute requirement for glucose

A

RBCs, lens of the eye, medulla of the kidney and neutrophils

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2
Q

at what glucose plasma level does death and brain damage result from

A

0.6 mmol/L

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3
Q

what can be used in blood tests to determine plasma glucose levels

A

HbA1c

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4
Q

what is glucose stored as

A

glycogen

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5
Q

what does muscle glycogen supply

A

glucose to skeletal muscle cells

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6
Q

what does liver glycogen supply

A

glucose to the body

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7
Q

describe the structure of glycogen

A

there is a central protein glycogenin with glucose residues branching off linked by alpha-1,4 and alpha-1,6 glyosidic bonds

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8
Q

what is glycogenesis

A

to production of glycogen

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9
Q

outline glycogenesis

A
  • 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
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10
Q

which 2 enzymes can add the glucose residue from the UDP-glucose onto the glycogen molecule

A
  • glycogen synthase for alpha-1,4 bonds

- branching enzyme for alpha-1,6 bonds

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11
Q

what is glycogenolysis

A

breakdown of glycogen

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12
Q

outline glycogenolysis

A
  • G1P is released from the glycogen by glycogen phosphorylase or de-branching enzyme
  • G1P is converted into G6P by phosphoglucomutase
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13
Q

true or false: glycogenolysis is the reversal of glycogenesis

A

false - different enzymes allow inhibition and stimulation of the different pathways

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14
Q

what happens to the G6P produced by liver cells

A

converted into glucose and released into the blood for use by other tissues

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15
Q

what happens to the G6P produced by muscle cells

A

used by muscle cells in glycolysis for energy production

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16
Q

what enzyme in the liver converts G6P into glucose

A

glucose-6-phosphatase

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17
Q

what is the rate limiting enzyme in glycogen synthesis

A

glycogen synthase

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18
Q

what is the rate limiting enzyme in glycogen degradation

A

glycogen phosphorylase

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19
Q

what hormone increases the activity of glycogen synthase

A

insulin

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20
Q

what hormone increases the activity of glycogen phosphorylase

A

glucagon

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21
Q

true or false: AMP is an allosteric activator of glycogen phosphorylase

A

true - but only in the muscles not in the liver

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22
Q

give 2 examples of glycogen storage diseases

A
  1. von Gierke’s disease

2. McArdle disease

23
Q

what is von Gierke’s disease

A

deficiency in glucose 6 phosphatase

24
Q

what is McArdle disease

A

deficiency in muscle glycogen phosphorylase

25
Q

what is gluconeogenesis

A

production of glucose

26
Q

what are the 3 major precursors of glucose

A
  • lactate
  • glycerol
  • amino acids
27
Q

where does gluconeogenesis occur

A

liver (and also the kidney)

28
Q

in what cycle is lactate used in respiration

A

cori cycle

29
Q

outline the cori cycle

A

glucose is converted into lactate in muscle which then travels in the blood to the liver where its converted back to glucose

30
Q

what are the 3 key enzymes in gluconeogensis

A
  • glucose-6-phosphatase
  • fructose 1,6-bisphosphatase
  • PEPCK
31
Q

what does glucose-6-phosphatase do

A

converts G6P into glucose

32
Q

what does fructose-1,6-bisphosphatase do

A

converts fructose 1,6-bisphosphate into G6P

33
Q

what does PEPCK do

A

converts oxaloacetate into phosphoenolpyruvate

34
Q

which hormone stimulates gluconeogensis

A

glucagon and cortisol

35
Q

which hormone inhibits gluconeogenesis

A

insulin

36
Q

what are lipids stored as

A

triacylglycerides

37
Q

where are triacylglycerides stored

A

in adipose tissue

38
Q

when are triacylglycerides used for energy

A

in prolonged exercise, pregnancy, stress and starvation

39
Q

what enzyme breaks down triacylglycerides

A

pancreatic lipases

40
Q

what are triacylglycerides broken down into

A

fatty acids and glycerol

41
Q

what happens to the fatty acids and glycerol in intestinal epithelia cells

A

they are reformed to TAGs then converted into chylomicrons where the enter the lymph system

42
Q

where do the chylomicrons drain into the blood

A

left subclavian vein

43
Q

what hormone mobilised TGA metabolism

A

glucagon and adrenaline

44
Q

what hormone inhibits the metabolism of TGAs

A

insulin

45
Q

what happens to the TGAs in the blood

A

they can either be stored in adipose tissue or used in fatty acid oxidation

46
Q

what is lipogenesis

A

fatty acid synthesis

47
Q

where does lipogenesis occur

A

liver

48
Q

outline lipogenesis

A
  • 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
49
Q

what enzyme converts Acetyl CoA into malonyl CoA

A

Acetyl-CoA carboxylase

50
Q

what enzyme complex uses malonyl CoA to produce fatty acids

A

fatty acid synthase complex

51
Q

where does fatty acid synthesis occur

A

cytoplasm

52
Q

true or false; only small amounts of energy are required in lipogenesis

A

false

53
Q

what enzyme regulates lipogenesis

A

acetyl-CoA carboxylase

54
Q

what hormone stimulates lipogenesis

A

insulin

Phase 1 - S2 Metabolism, Endocrinology, Haematology (22 decks)

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