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Energy storage Flashcards

(62 cards)

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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
how does insulin affect glycogen synthase activity
increases
26
how does insulin affect glycogen phosporylase activity
decreases
27
give two examples of glycogen storage diseases
von Gierke's disease (glucose-6-phosphotase deficiency) McArdle disease (muscle glycogen phosphorylase deficiency)
28
what is gluconeogenesis
production of new glucose
29
when does gluconeogenesis occur
after 8 hours of fasting liver glycogen stores start to deplete
30
where does gluconeogenesis occur
liver to some extent the kidney medulla
31
what are the three precursors for gluconeogenesis
- lactate (Cori cycle) - glycerol - amino acids
32
why can acetyl CoA not be used for gluconeogenesis
pyruvate dehydrogenase reaction is irreversible so cannot be converted to pyruvate
33
what does the enzyme PEPCK do
converts oxaloacetate to phospholpyruvate
34
what are glucogenic amino acids converted to for gluconeogenesis
pyruvate or oxaloacetate
35
what is lactate converted to for gluconeogenesis
pyruvate
36
what is glycerol converted to for gluconeogenesis
dihydroxyacetone to fructose 1,6- bisphosphate
37
what are the three enzymes in gluconeogenesis
- PEPCK - fructose-1,6-bisphosphoatase - glucose-6-phosphatase
38
what are the two regulation enzymes in gluconeogenesis
- PEPCK - fructose-1,6-bisphophatase
39
what is the effect of glucagon and cortisol on PEPCK and F16P activity
increases
40
what is the effect of insulin on PEPCK and F16P activity
decreases
41
what is an adipocyte
large lipid droplet mainly containing TAG and cholesterol ester
42
what adaptation of adipocyte allows it to hold alot of fats
can expand as more fat added
43
how many times can adipocytes increase in size before a new cell is made
4
44
where does lipogenesis occur
liver
45
what is lipogenesis
lipid synthesis
46
why are triacylglycerols a good storage molecule
- anhydrous - energy content per gram twice that or carbs or proteins
47
what is the first step of lipogenesis
- citrate from TCA cycle leaves mitochondria as ACoA cannot be transported out mito (oxaloacetate +acetyl CoA) cleaved back into OAA and ACoA
48
what is the second step of lipogenesis for acetyl CoA
- acetyl CoA converted to Malonyl CoA by enzyme : acetyl CoA carboxylase using ATP
49
what is the second step of lipogenesis for oxaloacetate
converted to malate which is then converted to pyruvate by malic enzyme
50
what happens to malonyl CoA in lipogenesis
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
why is acetyl CoA converted to malonyl CoA
want to add 2C and but we loose one from CO2 so as malonyl is 3 C adds 2C after loss of CO2
52
what is the regulatory enzyme in lipogenesis
acetyl-CoA carboxylase
53
what is the effect. of insulin and citrate on acetyl CoA carboxylase activity
increases
54
what is the effect. of glucagon/ adrenaline/ AMP on acetyl CoA carboxylase activity
decreases
55
what is lipolysis
fat mobilisation
56
what enzyme is involved in lipolysis
hormone sensitive lipase
57
what does hormone sensitive lipase do
converts TAG stored in adipose tissue to glycerol and FA in blood
58
how does glucagon affect hormone sensitive lipase
activates
59
how does insulin affect hormone sensitive lipase
inhibits
60
what type of energy storage differs between a health weight and overweight
TAGs
61
what is the normal plasma glucose level
5mmol/L
62
what is hypoglycaemia
low plasma glucose levels

MEH (12 decks)

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