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bm210 biochemistry > D1 absorptive state > Flashcards

D1 absorptive state Flashcards

1
Q

what is glycolysis

A

seq of reactions that metabolises 1 mol of glucose to 2 mols of pyruvate
net production of 2 mols of ATP

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2
Q

glycolysis eqn

A

D-glucose+2NAD+2ADP+2Pi—2 pyruvate+2 ATP+2NADH+2H+2H20

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3
Q

what do the 2 phosphorylation rxns form

A

fructose 1,6-biphosphate

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4
Q

what 2 mols are cleaved from each fructose 1,6-biphosphate

A

triose phosphate

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5
Q

what 2 molecular rearrangements occur in glycolysis

A
  • 2 phosphorylations of ADP = 2 ATP per triose phosphate
  • 1 oxidation forming NADH per triose phosphate
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6
Q

whats the product per glucose

A

2 mols of pyruvate

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7
Q

what is phosphoryl transfer

A

transfer of a phosphoryl group from ATP to an alcohol

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8
Q

what occurs after phosphoryl transfer

A

alcohol gives up the hydrogen while ADP and an organic phosphate are yielded

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9
Q

what is aldose ketose isomerisation

A

conversion of an aldose (glucose) to a ketose (fructose) or a ketose to an aldose

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10
Q

what is alcohol hydrogen transferred to and what does this result in

A

to the oxygen in the aldehyde group transforming the original alcohol group to a carbonyl and the original aldehyde to an alcohol

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11
Q

what is aldol cleavage

A

splitting of a carbon-carbon bond

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12
Q

what does aldol cleavage yield

A

an aldehyde and a ketose

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13
Q

what is a phosphoryl shift

A

movement of a phosphoryl group from oxygen to an alcohol oxygen in the same mol

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14
Q

result of a phosphoryl shift

A

alcohol hydrogen is removed and binds to the formerly phosphorous bound oxygen

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15
Q

what is dehydration

A

removal of a water mol from an alcohol

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16
Q

what does dehydration yield

A

a carbon-carbon double bond in the original mol

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17
Q

how many rxns take place during glycolysis

A

10 rxns

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18
Q

what balance in the cell has to be maintained during glycolysis

A

redox balance

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19
Q

how is NAD* regenerated

A

through metabolism of pyruvate

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20
Q

what happens without regeneration of NAD*

A

glycolysis will stop

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21
Q

what is the dual role of the glycolytic pathway

A
  1. degradation of glucose to generate ATP
  2. provision of building blocks for synthetic reactions eg fatty acids
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22
Q

what can be sites of control in glycolytic pathway

A

enzymes catalysing irreversible reactions are potential sites of control

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23
Q

what are the control sites in glycolysis

A

-hexokinase
-phosphofructokinase
-pyruvate kinase

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24
Q

hexokinase control site

A

inhibited by its product glucose 6-phosphate

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25
Q

phosphofructokinase control site

A

committed step
inhibition by; ATP, low pH, citrate;activation by; AMP and fructose 2,6-bisphosphate

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26
Q

pyruvate kinase control site

A

ATP and alanine inhibit; fructose 1,6-bisphosphate activates

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27
Q

origin of fructose 2,6-bisphosphate

A

generated by phosphofructokinase 2

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28
Q

what is phosphofructokinase 2

A

bifunctional enzyme responsible for synthesis and hydrolysis of fructose 2,6-biphosphate into
phosphofructokinase-phosphofructobisphosphatase

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29
Q

how is phosphofructokinase 2 regulated

A

reciprocal control by phosphorylation of serine 460 by protein kinase a

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30
Q

what is active in phosphorylated form

A

phosphatase

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31
Q

what is active in dephosphorylated form

A

kinase

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32
Q

what happens to pyruvate in anaerobic setting

A

converts to ethanol

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33
Q

lactic acid fermentation occurs how

A

pyruvate into lactate by a reduction rxn using lactate dehydrogenase

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34
Q

what is lactate produced by

A

muscles when the body cannot supply enoughoxygen

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35
Q

what lacks mitochondria and so cannot oxidise glucose completely

A

erythrocytes

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36
Q

body can create more ATP at a cost of what

A

creating an oxygen debt

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37
Q

what must lactate be converted back into

A

pyruvate

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38
Q

what does glycogen function as

A

reserve of glucose when metabolic demand for glucose outpaces the cells ability to obtain it from extracellular sources

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39
Q

what does controlled release of glucose from glycogen maintain

A

blood glucose levels

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40
Q

main storage of glycogen

A

liver and skeletal muscle

40
Q

main storage of glycogen

A

liver and skeletal muscle

41
Q

what is glycogen very similar to

A

amylopectin
but more branches from every 10th glucose

42
Q

what are the two names of the stages of glycogen anabolism

A

initiation and elongation

43
Q

what is the initiation stage of glycogen synthesis catalysed by

A

catalysed in an autocatalytic manner by glycogenin

44
Q

what is the elongation stage of glycogen synthesis catalysed by

A

by glycogen synthase in concert with the branching enzyme

45
Q

what is glycogenin

A

enzyme involved in glycogen biosynthesis

46
Q

what is glycogenin classified as

A

glycosyl-transferase

47
Q

what does glycogenin act as

A

the primer to which further glucose monomers can be added

48
Q

how does glycogenin bind glucose

A

from UDP-glucose to a hydroxyl group of tyrosine 194

49
Q

what is glycogen synthase (GS)

A

main enzyme involved in glycogen polymerisation

50
Q

GS can only be added to what

A

an existing chain of at least 8 glucose residues (elongation stage)

51
Q

GS regulated by

A

covalent modifications and an allosteric mechanism

52
Q

what 2 things is GS phosphorylated by

A

protein kinase A
glycogen synthase kinase 3 (GSK3)

53
Q

what does phosphorylation convert GS into

A

active a form into inactive b form

54
Q

when is b form still active

A

when a high level of the allosteric activator glucose 6-phosphate is present

55
Q

what is the activated form of glucose that is the immediate precursor for glycogen synthesis

A

uridine diphosphate glucose (UDP-glucose)

56
Q

what are nucleotide diphosphate sugars precursors for

A

synthesis of complex carbohydrates
including oligosaccharide chains of glycoproteins

57
Q

what is UDP-glucose formed from

A

glucoses-1-phosphate

58
Q

overall eqn for UDP-glucose synthesis

A

glucose-1-phosphate+UTP=UDP-glucose+2Pi

59
Q

is the rxn for UDP-glucose reversible or irreversible

A

irreversible

60
Q

what makes the UDP-glucose rxn irreversible

A

spontaneous hydrolysis of the ~P bond in pyrophosphate PPi (P~P) drives the overall rxn

61
Q

what is the only energy cost for glycogen synthesis

A

cleavage of PPi
(one~P bond per glucose residue)

62
Q

where are glucose residues added to

A

non-reducing terminal residues of glycogen

63
Q

what is the rxn product released from UDP-glucose

A

UDP

64
Q

what is the linkage formed from glycogen synthesis

A

a-1,4-glycosidic linkage

65
Q

what is amylo (1,4-1,6) transglycosylase

A

branching enzyme

66
Q

how many residues and from where is transferred to a more interior site

A

7 residues from the non reducing end of the chain

67
Q

what must the block include

A

non reducing terminus

68
Q

what linkage and where are the 7 residues attached by

A

a-(1,6) linkage at least 4 residues from the nearest branch point

69
Q

why is branching so important

A

increases solubility of glycogen

70
Q

what does branching allow

A

generation of a large osmotically inactive storage form of glucose

71
Q

what does branching create

A

large number of terminal residues

72
Q

terminal residues are at the sites of action of what 2 enzymes

A

glycogen phosphorylase
glycogen synthase

73
Q

what does branching increase the rate of

A

glycogen synthesis and degradation

74
Q

where are fatty acids synthesised

A

cytoplasm

75
Q

why are fatty acids synthesised in the cytoplasm of a fed state

A

more carb (hence acetyl CoA) is available than needed for the TCA cycle

76
Q

what is required to build new fatty acids

A

ATP

77
Q

what protein remains bound to the intermediates in fatty acid synthesis

A

acyl-carrier protein (ACP)

78
Q

how does the fatty acid chain grow by

A

sequential addition of 2 carbon units derived from acetyl CoA

79
Q

what is the activated donor of fatty acid synthesis

A

malonyl-ACP

80
Q

what is the transfer driven by and what is released in fatty acid synthesis

A

a decarboxylation reaction releasing CO2

81
Q

what are fatty acids stored as

A

triacylglycerides (TG)

82
Q

what are the 2 building blocks of fatty acid biosynthesis
and what does it result in

A

1 acetyl CoA
7 malonyl CoA
= palmitate (C16)

83
Q

what enzyme catalyses formation of malonyl CoA

A

acetyl CoA carboxylase

84
Q

is the formation of malonyl CoA reversible or irreversible

A

irreversible
committed step

85
Q

what is the bond that joins the glycerol mol to the fatty acids

A

ester bond

86
Q

is triacylglycerol high or low energy

A

high energy storage biomolecule

87
Q

how man kJ/g of fat is in a triacylglycerol mol

A

39

88
Q

components of a triacylglycerol mol

A

3 fatty acid groups
glycerol-3 phosphate

89
Q

3 places that TGs are synthesised

A

liver
adipose tissue
intestinal tract

90
Q

how is TG synthesis carried out in the liver

A

from fatty acids made using glucose (glycolysis) or aa side chains

91
Q

TG synthesis during transport of dietary fat (what type)

A

intestines and adipose tissue

92
Q

can TG cross the cell membrane

A

no

93
Q

how does TG get in and out of cells

A

has to be broken down by lipases

94
Q

how are TG carried around the body

A

by lipoproteins in the plasma

95
Q

how is TG carried from liver to peripheral tissues

A

very low density lipoprotein
VLDL

96
Q

how is TG carried from intestine to peripheral tissues

A

chylomicrons

97
Q

how is each fatty acid activated

A

thiol group of CoA forms high energy thioester bond with the carboxylic acid group of the fatty acid

98
Q

what is the energy source in activation of FA

A

ATP (2 high energy bonds used)

bm210 biochemistry (19 decks)

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