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MedBiochem > quiz 2.3 glycogen > Flashcards

quiz 2.3 glycogen Flashcards

1
Q

weight contribution of glycogen in the liver and skeletal muscle

A

20% in liver

1-2% in skel muscle

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2
Q

muscle glycogen quickly provides energy during when

A

strenuous exercise like studying, practicals, thesis-ing

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3
Q

explain itsura ng glycogen

A

sorage form of glucose, highly branched polysacch of glucose linked via alpha 1-4 bonds with alpha 1-6 branches every 8-10

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4
Q

the only anomeric carbon that is not linked to another glucose residue that is located at the beginning

A

glycogenin

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5
Q

features of glycogenin

A

only anomeric carbon

@ the beginning of the polysacch chain

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6
Q

starting point of glycogen synthesis

A

formation of gluc-6-PO4

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7
Q

2nd step in glycogen synth

A

glucose-6-PO4 is converted to gluc-1-PO4 by phosphoglucomutase

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8
Q

in the 2nd step, gluc-4-PO4 is converted to ______ by _______

A

gluc-1-PO4

phosphoglucomutase

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9
Q

in the 3rd step, gluc-1-PO4 is converted to ___ by ____

A

UDP-glucose

UDP-glucose pyrophosphates

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10
Q

the 3rd step is highly exergonic so it ensures that the UDP-glucose pyrophosphate proceeds in the direction of formation of

A

UDP-glucose

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11
Q

immediate donor of glucose residues in the reaction catalyzed by glycogen synthesis

A

UDP-glucose

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12
Q

this enzyme promotes the transfer of the glucose residue from UDP-glucose to the nonreducing end of a branched glycogen molecule

A

glycogen synthase

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13
Q

a primer in glycogenesis acts as what or how

A

acceptor of glucose residue from UDP-glucose

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14
Q

possible primers in glycogen synthesis

A

pre-formed alpha 1-4 polyglucose or branch having at least 8 gluc residues (glycogen fragment)

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15
Q

in the absence of a glycogen fragment, _ can act as glucose residue acceptor

A

glycogenin

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16
Q

serves as the site where the initial glucosyl unit is attached

A

side chain -OH os a spefici tyrosine in glycogenin

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17
Q

whta catalyzes the attachment of the glucosyl unit in the side chain OH of specific tyrosine in the glycogenin

A

glycogenin thru autoglucosylation

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18
Q

the rxn of the sequential addition of seven more glucose residues derived from UDP-glucose is catalyzed by the __________ activity of glycogenin

A

chain-extending

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19
Q

the elongation of glycogen involves the transfer of glucose from DUG-glucose ti the _______ of the growing chain

A

nonreducing end

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20
Q

the enzyme responsible for making the linear linkages in glycogen

A

glycogen synthase

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21
Q

what forms the branch points of glycogen

A

amylo(1-4) to (1-6) transglycosylase/ glycogen 4-6 transferase

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22
Q

catalyzes the transfer of 6 or 7 glucose residues from the nonreducing end of a glycogen branch having at least 11 residues to the C-6 OH group of a glucose reside at a more interior portion of the same or another glycogen chsin

A

amylo(1-4) to (1-6) transglycosylase/ glycogen 4-6 transferase

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23
Q

biological effect of branching is to make the glycogen ___

A

more soluble and to increase number of nonreducing ends

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24
Q

3 enzymes involved in glycogenolysis

A

glycogen phosphorylase
glycogen debranching enzyme
phosphoglucomutase

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25
Q

catalyzes the rxn in which the alpha 1-4 glycosidic linkage between two glucose residues at a nonreducing end of glycogen undergoes attack by inorganic phosphate

A

glycogen phosphorylase

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26
Q

essential cofactor for the glycogen phosphorylase rxn

A

pyridoxal phosphate

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27
Q

glycogen phosphatase removes what

A

terminal glucose residue as alpha-D-glucose-PO4

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28
Q

where does the action of glycogen phosphorylase stop

A

4 glucose away from a branch point

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29
Q

after the Ction of glycogen phosphorylase, what enzyme removes the glucose residues near a branch pointw

A

debranching enzyme aka oligo(a1-6) to (a1-4) glucan-transferase

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30
Q

first step in debranching enzyme

A

transfer a 3-block glucose to a nonreducing end

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31
Q

two activities of the debranching enzyme

A

transferase

(a1-6) glucosidase

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32
Q

2nd step in debranching enzyme

A

release the single glucose residue at the branhpoint

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33
Q

after the action of debranching enzyme, ano sunod

A

glycogen phosphorylase again

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34
Q

the gluc1PO4 by glycogen phosphorylase is converted in the ___ to ____ by _____

A

cytosok
gluc6PO4
phosphoglucomutase

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35
Q

in the liver, the gluc6PO4 is transported to the ____ by _____

A

ER

gluc6PO4 translocase

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36
Q

in the ER of hepatocytes, the gluc6PO4 is converted to ___ by ____

A

glucose

gluc6PO4ase

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37
Q

in the muscles during need for energy, ano fate ng gluc6PO4

A

enters glucolysis

not released to blood coz no gluc6PO4ase

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38
Q

binding of what hormones signal the need for glycogen degradation

A

glucagon

epineph

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39
Q

ano signal transduction shit ng hormone regulation ng glycogenesis and lysis

A

PKA
adenylyl cyclase
cAMP

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40
Q

the active state of the phosphorylase kinase and phosphorylase maintained bcoz ____ is inhibited by the proteins also phosphorylates by cAMP w

A

protein phosphatase-1

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41
Q

how does insulin oppose the effects of glucagon and epinephrine

A

actiavtes phosphodiesterase that degrades cAMP and activates PP1

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42
Q

in liver, free glucose is also an allosteric inhibitor of ______ making it a better substrate for PP1

A

glycogen phsphorylase

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43
Q

glycogen storage dse: no glycogen synthase

A

type 0

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44
Q

glycogen storage dse: low gluc6PO4

A

type 1a (von Gierke’s)

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45
Q

glycogen storage dse: loe lysosomal glucosidase

A

type II (Pompe’s)

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46
Q

glycogen storage dse: glycogen storage dse: low debranching enzyme

A

type III (Cori’s or Forbe’s)

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47
Q

glycogen storage dse: low branching

A

type IV (Andersen’s)

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48
Q

glycogen storage dse: low muscle phosphorylase

A

type V McArdle’s

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49
Q

glycogen storage dse: low liver phosphorylase

A

type VI Hers’

50
Q

alternate pathway for metab pf glucose

A

pentose phosphate pathway/HMP

51
Q

two major function of HMP/PPP

A

formation of NADPH for synthesis of fatty acids and steroids

synthesis of ribose for nucleotide and nucleic acid formation

52
Q

which phase of HMP/PP is reversible

A

nonoxidative phase

53
Q

what are formed in the oxidative phase of PP/HMP

A

ribulose-5-PO4
CO2
2 mol. of NAPDH

54
Q

1st step in PPP/HMP

A

gluc6PO4 is converted to 6-phosphogluconalactone by G6PD

55
Q

in the 1st step of the PP/HMP, gluc6PO4 is ultimately converted to ___

A

6-phosphogluconate

56
Q

potent competitive inhibitor of G6PD

A

NADPH

57
Q

when there is an increased demand for NADPH, the NADPH/NADP ratio decreases and the flux of the forward rxn increases in response to _______

A

enhacned activity of G6PD

58
Q

6-phosphogluconolactone is hydrolyzed to the _____ by a specific ____

A

free acid 6-phosphogluconate

59
Q

in the 1st step, gluc6PO4 is initially converted to _____ by _____

A

6-phosphogluconolactone

G6PD

60
Q

2ns step in PPP/HMP

A

oxidative decarboxylation of 6-phosphogluconate to ribulose-5-PO4 by 6-phosphogluconate dehydrogenase

61
Q

the irreversible rxn of the oxidative decarboxylation og 6-phosphogluconate forms what

A

ribulose-5-PO4
CO2
2nd NADPH

62
Q

the reversible nonoxid rxns of the PP/HMP allows the formation of

A

ribose-5-PO4
fructose-6-PO4
glyceraldehyde-3-PO4

63
Q

first step in the non-oxid rxns of PPP/HMP

A

ribulose-5-PO4 is converted to xylulose-5-PO4 by ribulose-5-PO4 3-epimerase

64
Q

in one rxn in the 1st nonoxid phase of PPP/HMP, ribulose-5-PO4 is converted to ____ by ____

A

xylulose-5-PO4

ribulose-5-PO4 3-epimerase

65
Q

in the another nonoxid rxn of the HMP/PPP for nucleotide and nucleic acid synthesis, ribulose-5-PO4 is converted to _____ by _____

A

ribose-5-PO4

ribose-5-PO4 ketoisomerase

66
Q

two enzymes unique to the PPP that act in the interconversion of sugars

A

transketolase

transaldolase

67
Q

the enzyme transketolase requires which coenzyme

A

TPP

68
Q

in the PP, what transfers the C1 and C2 of xylulose-5-PO4 to ribose-5-PO4

A

transketolase

69
Q

in the 1st transketolase rxn of PPP/HMP, the xylulose-5-PO4 and ribose-5-PO4 are converted to

A

glyceraldehyde-3-PO4

sedoheptulose-7-PO4

70
Q

in the transaldolase rxn, 3-carbon fragment from sedoheptulose-7-PO4 is condensed with glyceraldehyde-3-PO4 and then turned to

A

fructose-6-PO4

erythrose-4-PO4

71
Q

in the 2nd transketolase rxn of PPP, _________ is converted to _______

A

xylulose-5-PO4 and erythrose-4-PO4

glyceraldehyde-3-PO4 and fructose-6-PO4

72
Q

in summary, the non-oxid rxns of PPP uses ________ to form _______

A

6 pentoses

5 hexoses

73
Q

in which pathway does glucose become glucoronic acid, ascorbic acid, and pentoses

A

uronic acid athway

74
Q

does the PPP/HMP lead to ATP formation

A

no

75
Q

does the uronic acid pathway lead to ATP production

A

no

76
Q

1st step in uronic acid path

A

gluc6PO4 is isomerized to gluc1PO4 > reacts with UTP to form UDPGluc by UDPGluc phosphorylase

77
Q

what enzyme is used in the formation of UDPGluc from UTP and gluc1PO4

A

UDPGluc phosphorylase

78
Q

when forming the UDP-glucoronate, what happens to UDPGlc

A

oxidized @ C6 by UDPGlc dehydrogenase

79
Q

2nd step of uronic acid path

A

UDPGlc oxidized to UDP-glucoronate

80
Q

what oxidized the C6 at UDPGlc in the 2nd step of uronic acid pathway

A

NAD-dependent UDPGlc dehydrogenase

81
Q

direct precursor of ascorbic acid

A

L-gulonate

82
Q

3rd step in the uronic acid path

A

glucoronate is reduced to L-gulonate

83
Q

in the 3rd of the uronic acid path, glucoronate is reduced to

A

L-gulonate

84
Q

why can’t ascorbic acid be synthesized in humans

A

absence of L-gulonolactone oxidase

85
Q

enzyme used to synthesize ascorbic acid from L-gulonate

A

L-gulonolactone oxidase

86
Q

in the last series of steps of the uronic acid pathway, l-gulonate is oxidized to

A

3-keto-L-gulonate

87
Q

in the last series of steps of the uronic acid pathway, 3-keto-L-gulonate is decarboxylated to L-xylulose

A

L-xylulose

88
Q

L-xylulose is converted to the D isomer by an NADPH-dependent reduction to _

A

xylitol

89
Q

component of the uro nic acid pathway that is metabolized further in the PPP/HMP

A

D-xylulose-5-PO4

90
Q

this is the ‘busog ka na’ hormone

A

leptin

91
Q

first step in fructose metab

A

phosphorylation of fructose

92
Q

what catalyzes the phoshporylation of fructose

A

fructokinase/hexokinase

93
Q

hexokinase has a ____ affinity for fructose

A

low

94
Q

action of fructokinase

A

fructose to fruc-1-PO4

95
Q

2ns step in fructose metab

A

cleavage of furctose-1-PO4 to DHAP and glyceraldehyde

96
Q

what catalyzes the 2nd step of the fructose metab

A

aldolase B aka fructose-1-PO4 aldolase

97
Q

why is fructose metab faster than glucose metab

A

fructose metab bypass PFK-1 rxn

98
Q

which component of the fructose metab can more readily enter the glycolysis pathway

A

DHAP

99
Q

what converts glyceraldehyde to glyceraldehyde-3-PO4

A

triose kinase

100
Q

insulin-independent organs

A

BRICK-L

brain
RBCs
intestine
cornea
kidney
liver
101
Q

insulin-dep organs

A

adipose

muscles

102
Q

major carb source of sperm cells

A

fructose

103
Q

how to make fructose from glucose

A

via sorbitol

glucose > aldose reductase > sorbitol > sorbitol dehydrogenase

104
Q

saan organs pwede pa maging fructose ung sorbitol

A

seminal vesicles
liver
ovaries

105
Q

sobitol aka

A

polyol

106
Q

explain cataracts, peripheral neuropathy, microvascular problems leading to nephropathy and retinopathy in diabetes

A

accumulation of sorbitol > water retention > swelling

107
Q

autosomal defiency of fructokinase

A

essential fructosuria

108
Q

aldoalse B deficiency

A

hereditary fructose intolerance

109
Q

symptoms/complciations of HFI

A

severe hypoglycemia
hepatomegaly due to accumulation
renal dysfunction

110
Q

ang essential fructosuria malignant or benign condition

A

benign

whut

111
Q

galactose metabolism explain mo na bes para sa ikauunlad ng bansa

A

galactose > (galactokinase) > glactose-1-PO4 > (glactose-1-PO4 uridylyltransferase/GALT/GAL1PUT) > UDP-galactose > (UDP-hexose 4 epimerase) > UDP-glucose

112
Q

GALT deficiency

A

classic galactosemia

113
Q

a metab due to accumulation of galactose,causing cataracts and etc

A

galactitol

114
Q

dse where there is accumulation of galactitol

A

galactokinase deficiency

115
Q

one of the most blabla na caused b y accumulation of galactitol

A

cataract

116
Q

how is mannose converted to fructose6PO4

A

mannose > mannose6PO4 > (phosphomannose isomerase) > fructose6PO4

117
Q

where synthesis ng lactose

A

golgi apparatus by lactose synthase

118
Q

lactose synthase aka

A

UDP-galactose:glucose galactosyltransferase

119
Q

which of protein of lactose synthase involved sa formation of N-acetyllactosamine

A

protein A

120
Q

which protein of lactose sythase involved sa formation ng prolactin

A

protein B

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