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1 STEP Uworld biochemistry > Biochemistry general > Flashcards

Biochemistry general Flashcards

1
Q

Pellagra 3Ds? +one additional symptom

A

Diarrhea, Dementia, Dermatitis (C3/C4); + hyperpigmentation of sun-exposed limbs.

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2
Q

Diarrhea + Dementia + Dermatitis =?

A

Pellagra, when B3 (niacin) deficiency

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3
Q

Katabolic reactions where NAD participates?

A

Glycolysis and beta-oxidation

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4
Q

Anabolic reactions where NADP participates?

A

Cholesterol and fatty acid synthesis

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5
Q

B3 is derived from ……

A

Tryptophan

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6
Q

When/how often present symptoms in G6PD deficiency?

A

Episodically, when oxidative stress is increased

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7
Q

NAD and NADP are important cofactors for ……… and ………. enzymes.

A

Reductase and dehydrogenase

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8
Q

Apart from the catabolic reactions, NAD is needed for …………….. (2)

A

Cell signaling and DNR repair

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9
Q

NAD is a key constituent in …………..

A

TCA cycle

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10
Q

In TCA NAD is used ……. (3 reactions)

A

isocitrate dehydrogenase, alfa-ketoglutarate dehydrogenase, malate dehydrogenase

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11
Q

Precursor for nucleotide synthesis in PPP?

A

Ribose-5-P

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12
Q

In PPP are produced NADPH. Where is it used? (2)

A

Fatty acids and cholesterol synthesis

Glutathione antioxidant mechanism

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13
Q

What vitamins are needed for vit. B3 synthesis? (2)

A

B2 and B6

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14
Q

What 3 states can lead to pellagra apart usual deficiency of B3?

A

Hartnup disease
Malignant carcinoid syndrome (incr. tryptophan metabolism)
Isoniazid (decr. B6 - which is needed for B3 synthesis)

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15
Q

The fate of pyruvate depends on …………..

A

the concentration of the oxygen in the tissue.

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16
Q

In presence of oxygen, pyruvate …………

A

is converted to Acetyl-CoA and goes to TCA cycle.

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17
Q

In the absence of oxygen, pyruvate ………

A

in converted to lactate in the cytosol.

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18
Q

What reaction stops and induces pyruvate convertion to lactate in hypoxic conditions?

A

Pyruvate dehydrogenase is inhibited by NADH. This NADH is consumed in reaction pyruvate to lactate and converted to NAD.

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19
Q

What enzymes are unidirectional and bypass gluconeogenesis? (3)

A

hexokinase, phosphofructokinase-1, and pyruvate kinase

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20
Q

What is the principal step in gluconeogenesis?

A

pyruvate to oxaloacetate by pyruvate carboxylase + B7

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21
Q

Fasting. When is gluconeogenesis and when glycogenolysis?

A

Glycogenolysis: first 12-18h
Gluconeogenesis: after 18-24h

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22
Q

first reaction glycogenolysis in starvation?

A

breakage of 1-4 glycosidic linkage to form G-1-P

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23
Q

the majority of ATP is produced in ……..

A

TCA in mitochondria

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24
Q

What reaction is substrate-level phosphorylation?

A

Succinyl CoA –> Succinate via Succinyl-CoA synthase

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25
Q

What molecule is produced in the reaction of substrate-level phosphorylation?

A

GTP

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26
Q

Where is used a molecule that is produced in the reaction of substrate-level phosphorylation? (2)

A

Oxalate to PEP via phosphoenolpyruvate carboxykinase
or
ADP merge to GTP producing ATP

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27
Q

Neurological + lactatic acidosis + inc. serum alanine =?

A

Pyruvate dehydrogenase deficiency

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28
Q

What 2 amino acids are ketogenic?

A

Lysine and leucine

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29
Q

The diet for pyruvate dehydrogenase patients is consisted of: …………..

A

ketogenic diet: low carbo, high fat and medium proteins

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30
Q

When manifest symptoms of pyruvated dehydrogense deficiency?

A

infancy

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31
Q

B2 containing coenzymes constituent in …………….

A

electron transport chain

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32
Q

What reaction in TCA produces FADH2?

A

Succinate to fumarate

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33
Q

Which reaction is inhibited in TCA if there is lack of B2?

A

Succinate to fumarate

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34
Q

Which reaction of TCA is in electron transport chain? Why?

A

succinate to fumarate. Because produce FADH, which is electron carrier.

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35
Q

Riboflavin –> FMN. How called reaction?

A

phosphorylation

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36
Q

FMN –> FAD. How called reaction?

A

phosphorylation

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37
Q

Where can be used FMN? (2)

A

integrated in a coenzymes-flavin complex

convertion to FAD

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38
Q

FMN participate in …… complex

A

Complex I

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39
Q

FAD participate in …… complex

A

Complex II

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40
Q

Which complex participate in both TCA and electron transportation chain?

A

Complex II, FAD is cofactor.

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41
Q

Riboflavin deficiency symptoms?

A

cheilitis, angular stomatitis, eye defects: keratitis, neovascularization in cornea; seborrheic dermatitis, glossitis.

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42
Q

Reduced forms of FMN and FAD?

A

FMNH2 and FADH2

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43
Q

Muscle weakness + hypoketotic hypoglycemia + hypotonia =?

A

Primary carnitine deficiency

44
Q

What process is impaired in carnitine deficiency?

A

Fatty acid transfer from cytoplasm to mitochondrial matrix

45
Q

Why there is muscle weakness in carnitine deficiency?

A

No Acetyl-CoA from FA–> no production of ATP in TCA, therefore no energy.

46
Q

Why there is decr. ketone bodies in carnitine deficiency?

A

No Acetyl-CoA from FA –> liver cannot produce ketone bodies during fasting periods

47
Q

What catalyzes the first step of beta-oxidation?

A

Acyl-CoA dehydrogenase

48
Q

What accumulates in case of medium chain acyl-coA dehydrogenase deficiency?

A

fatty acyl carnitines in the blood

49
Q

vomiting+hypoketotic hypoglycemia+hepatomegaly/liver dysfunction + seizures/death=?

A

medium-chain acyl-coA dehydrogenase deficiency

50
Q

When manifest hypoglycemia and low ketone bodies levels in medium-chain acyl-coA deficiency?

A

during significant fast

51
Q

what is the treatment of MCAD?

A

avoid fasting, supply glucose during periods of illness

52
Q

when start ketone bodies form in adults?

A

after 1-2 fasting

53
Q

when children start to produce ketone bodies?

A

after 8-10 hours

54
Q

why in adults ketone bodies synthesis starts later than in children when fasting?

A

Children have limited glucose reserves

55
Q

what is the rate limiting enzyme in de novo fatty acid synthesis?

A

acetyl-coA carboxylase

56
Q

What enzyme in inhibites in well-fed state in liver?

A

ATP inhibits isocitrate dehydrogenase in hepatocytes

57
Q

In well-fed state there is high levels of ………….. in mitochondria, which goes to ………….

A

citrate goes to cytosol via citrate shuttle to form acetyl-coA

58
Q

What causes upregulation of Acetyl-coA caboxylase?(2)

A

high levels of citrate; elevated insulin caused by high carbohydrate intake

59
Q

What reaction catalyzes acetyl-coA carboxylase?

A

acetyl-coA –> malonyl-coA in the de novo fatty acid synthesis

60
Q

why mitochondrial membranes are impermeable to FA?

A

due to their negative charge

61
Q

how is prevented oxidation of newly synthesized de novo FA?

A

there is produced malonyl-coA, which inhibiths carnitine acyltrasferase

62
Q

how is prevented transportation of newly synthesized de novo FA into mitochondria matrix?

A

same as prevention of beta oxidation - malonyl coa inhibits carnitine acyltransferase

63
Q

Why there is a shift of reaction to ketone bodies production in case of starvation?

A

high levels of acetyl-coA and low levels of oxaloacetate, therefore TCA is inhibited. Then excessive AcylcoA is dericted to ketone bodies production

64
Q

what 2 molecules are produced in beta-oxidation?

A

FADH2 and NADH

65
Q

What molecule is needed for the synthesis of FA?

A

NADPH

66
Q

essential fructosuria symptoms? (2)

A

fructose in blood and urine. In general asymptomatic condition.

67
Q

What is alternative way to synthesize glucose in essential fructosuria?

A

Fructose –> fructose-6-P via hexokinase

68
Q

when manifest vomiting and hypoglycemia in hereditary fructose intolerance?

A

20-30min after fructose ingestion.

69
Q

why manifest hypoglycemia in hereditary fructose intolerance?

A

Hypoglycemia results from intracellular accumulation of fructose-1-phosphate and depletion of inorganic phosphate, which inhibit glycogenolysis and gluconeogenesis

70
Q

hypoglycemia + vomiting + failure to thrive + jaundice + cirrhosis/hepatomegaly =?

A

hereditary fructose intolerance

71
Q

3 main enzymes in fructose pathways?

A

fructokinase, aldolase B, triose kinase

72
Q

what metabolic process is inhibited when alcohol consumed?

A

gluconeogenesis

73
Q

alcohol does not inhibit glycogenolysis, but still eventually results in hypoglycemia, why?

A

at the beginning hepatic glycogenolysis is able to maintain euglycemia, however, after a prolonged time, glycogen is depleted, thus glucose in the blood also drops.

74
Q

why alcohol inhibits gluconeogenesis?

A

because consumes NAD which is needed for gluconeogenesis pathways.

75
Q

why lactate cannot be converted to pyruvate when alcohol is consumed?

A

lactate –> pyruvate requires NAD, which is reduced by alcohol dehydrogenase and aldehyde dehydrogenase. NADH/NAD ratio is increased, therefore pyruvate –>lactate use NADH

76
Q

advanced renal insufficiency results in hypoglycemia. Why?

A

Impaired clearance of insulin is a major contributor to hypoglycemia in patients with advanced renal insufficiency

77
Q

fructose is absorbed in intestines via …… transporter

A

GLUT5

78
Q

in fructokinase deficiency, …….. converts fructose into …. (compensation)

A

hexokinse; fructose-6-P

79
Q

fructose-6-P got from alternative pathway in its deficiency can be matabolized in ……….

A

glycolytic pathway

80
Q

why hereditary fructose intolerance is life threatening?

A

due to hypoglycemia

81
Q

what is manifestatin of hypoglycemia?

A

vomiting, lethargy, sweating, dehydration

82
Q

aldose reductase …….. (function)

A

converts glucose to sorbitol

83
Q

why under normal conditions aldose reductase does not produce sorbitol?

A

because it has low affinity for glucose.

84
Q

why breast milk can be used in fructose intolerance but not in galactosemia?

A

because it has maltose (2xglucose) and has lactose (glucose+galactose). No fructose - no problem. But it has galactose, therefore dangerous in galactosemia

85
Q

The man source of NADPH is ……

A

PPP

86
Q

where (body locations) is active PPP?

A

Cells, experiencing high oxidative stress (RBCs)
liver/adrenal cortex - they are involved in reductive biosynthesis of FA, cholesterol; also P450 metabolism
Phagocytic cell generating respiratory burst via NADPH oxidase

87
Q

the PPP pathway consists of ….. and …..

A

oxidative and nonoxidative reactions. function independently depending on cellular requirements

88
Q

body need nucleotides. how PPP works?

A

ribose-5-P is directed to nucleotide synthesis

89
Q

in PPP there is excess of ribose-5-P. what happens then?

A

reaction is directed to glycolysis intermediates synthesis (glyceralaldehyde-3-P and fructose-6-P) then joins to glycolysis to produce ATP

90
Q

oxidative PPP pathway cannot produce enough ribose-5-P. What happens?

A

nonoxidative pathway functions reverse; transketolase and transaldolase catalyze conversion of fructose-6-P and glyceraldehyde-3-P to ribose-5-P

91
Q

nonspecific test to detect fructose?

A

copper reducing test

92
Q

why copper reducing test can detect fructose?

A

because it is reducing sugar

93
Q

in GALK deficiency there is buildup of ………….

A

galactitol

94
Q

in GALT deficiency there is build up of ……….

A

toxic metabolites such galactose-1-P, galactitol

95
Q

Galactosemia + galactosuria + cataracts =?

A

galactokinase deficiency

96
Q

vomiting + feeding intolerance + hepatomegaly + jaundice + cataracts + intelectual diasbility =?

A

classic galactosemia

97
Q

When (age) manifest symptoms if there is deficiency in galactose pathway enzymes?

A

infants

98
Q

what induces symptoms in galactosemia?

A

breastfeeding

99
Q

in which metabolic disease may be e.coli sepsis?

A

classic galactosemia

100
Q

fumarate —> malate, enzyme?

A

fumarase

101
Q

succinyl-CoA —> succinate, enzyme?

A

succinyl thiokinase

102
Q

succinate –> fumarate, enzyme?

A

succinate dehydrogenase

103
Q

glyceraldehyde –> glyceraldehyde-3-P, enzyme?

A

triose kinase

104
Q

what 2 metabolic mechanisms are impaired in hereditary fructose intolerance? why?

A

inhibited glycogenolysis and gluconeogenesis. Due to the consumption of phosphate

105
Q

why urine dipstick is negative in hereditary fructose intolerance?

A

because it detects glucose, and here is defect in fructose pathway

1 STEP Uworld biochemistry (13 decks)

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