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USMLE Step 1-2015 > Biochem-Metabolism > Flashcards

Biochem-Metabolism Flashcards

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USMLE® Step 1 flashcards
1
Q

Mitochondria as metabolism site:

A

Fatty acid oxidation (B-oxidation), acteyl-coA production, TCA cycle, ketogenesis, oxidative phosphorylation (FAT KOP thought he was MITO)

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2
Q

Cytoplasm as metabolism site:

A

HMP shunt, glycolysis, steroid synthesis, protein synthesis, cholesterol synthesis

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3
Q

Both cytoplasm and mitochondria for metabolism?

A

Heme synthesis, Urea cycle, Gluconeogenesis (HUGs take two (i.e. both))

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4
Q

Process: Glycolysis
Rate limiting enzyme?
Regulators + and -

A

Phosphofructokinase-1 (PFK-1)
+AMP, fructose 2,6-biphosphate
-ATP, citrate

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5
Q

Process: Gluconeogenesis
Rate limiting enzyme?
Regulators + and -

A

Frustose-1,6,-bisphosphatase
+ ATP, acetyl-coA
-AMP, fructose 2,6-bisphosphate

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6
Q

Process: TCA cycle
Rate limiting enzyme
Regulators + and -

A

Isocitrate dehydrogenase
+ ADP
- ATP, NADH

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7
Q

Process: Glycogenesis
Rate limiting enzyme?
+ and - regulators

A

Glycogen synthase
+ Glucose-6-phosphate, insulin, cortisol
- Epinephrine, glucagon

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8
Q

Process: Glycogenolysis
Rate limiting enzyme?
+ and - regulators

A

Glycogen phosphorylase
+ Epinephrine, glucagon, AMP
-Glucose-6-phosphate, insulin, ATP

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9
Q

HMP shunt
Rate limiting enzyme
+ and - regulators

A

Glucose-6-phosphate dehydrogenase (G6PD)
+ NADP+
- NADPH

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10
Q

De novo pyrimidine synthesis
Rate limiting enzyme
+ and - regulator

A

CPS II
+ATP
-UTP

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11
Q

De novo purine synthesis
Rate limiting enzyme
+ and - regulator

A

Glutamine-PRPP-amidotransferase

-AMP, IMP, GMP

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12
Q

Urea cycle
Rate limiting enzyme
+ and - regulator

A

Carbomoyl phosphate synthetase I

+ N-acetylglutamate

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13
Q

Fatty acid synthesis
Rate limiting enzyme
+ and - regulator

A

Acetyl-CoA carboxylase
+ insulin, citrate
- glucagon, palmitoyl-CoA

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14
Q

Fatty acid oxidation
Rate limiting enzyme
+ and - regulator

A

Carnitine acyltrnasferase I

- malonyl-coA

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15
Q

Ketogenesis
Rate limiting enzyme
+ and - regulator

A

HMG-CoA synthase

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16
Q

Cholesterol synthesis
Rate limiting enzyme
+ and - regulator

A

+ Insulin, thyroxine

- glucagon, cholesterol

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17
Q

What monosaccharide is metabolized the fastest and why?

A

Fructose because it enters glycolysis after PFK-1 (a potent regulator of glycolysis)

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18
Q

What toxin causes glycolysis to produce zero net ATP?

A

Arsenic

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19
Q

Aerobic metabolism in heart/liver ATP production

A

32 ATP via malate/aspartate shuttle

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20
Q

Anaerobic metabolism in muscle ATP production

A

30 ATP via glycerol 3 phosphate shuttel

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21
Q

Universal electron acceptors?

A

NAD+, NADP+, FAD+

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22
Q

NAD+ is generally used in _____

A

Catabolic processes carry reducing equivalents away as NADH

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23
Q

NADPH generally used in?

What is it a producut of?

A
  • Anabolic processes, respiratory burst, cyp450, glutathione reductase
  • HMP shunt
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24
Q

Negative feedback on glucokinase production?

A

Fructose-6-phosphate

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25
Q

Negative feedback on hexokinase production?

A

Glucose-6-phosphate

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26
Q

Garlic breath, vomiting, rice-water stools

A

Arsenic poisoning

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27
Q

PDH complex and alphaketoglutarate dehydrogenase complex require what 5 same cofactors?

A

pyrophosphate (B1, thimaine;Tpp), Lipoic acid, CoA (B5, pantothenic acid), NAD (B3, niacin), FAD (B2, riboflavin)–>Tender Loving Care For Nobody

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28
Q

PDH complex is activated by exercise and how is it acvitvated?

A

Increase NAD+/NADH, Increase Calcium, Increase ADP

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29
Q

High Fructose 2,6 BP has what affect on alanine?

A

Prevents conversion of pyruvate to alanine in muscle and transport over to liver where it is converted back to pyruvate for use in gluconeogenesis (i.e. gluconeogenic conversion of alanine to glucose)

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30
Q

Only purely ketogenic amino acids

A

Lysine and leucine

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31
Q

Treatment of PDH complex deficiency and why?

A

Increase intake of ketogenic nutrients because they do not lead to formation of increase lactic acid and subsequently do not increase blood lactate levels

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32
Q

Fate of pyruvate generated during glycolysis is dependent on presence of oxygen. What happens with adequate or inadequate O2?

A

Adequate O2: Pyruvate–>Acetyl CoA

Inadequate O2: Pyruvate–>Lactate (increase lactate–>metabolic acidosis with compensatory respiratory alkalosis)

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33
Q

pyruvate to acetyl coA produces what?

A

1 NADH, 1 CO2

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34
Q

Function of ALT and cofactor

A

Alanine aminotransferase (B6): alanine carriers amino groups to liver from muscle

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35
Q

Function of PC and cofactor

A

Pyruvate carboxylase (biotin): oxaloacetate can replenish TCA cycle or be used in gluconeogenesis

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36
Q

function of Pyruvate dehdyrogenase and cofactor

A

(B1, B2, B3, B5, lipoic acid): transition from glycolysis to TCA cycle

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37
Q

Function of lactic acid dehydrogenase and cofactor

A

(B3): end of anaerobic glycolysis–>major pathway in RBC, WBC, cornea, lens, testes, kidney medulla

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38
Q

Function of lipoic acid

A

Serves in decarboxylation of alpha ketoacids and transfer of alkyl groups (ie. from pyruvate to coenzyme A)

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39
Q

Oxaloacetate–>Citrate

A

Citrate synthase

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40
Q

Isocitrate–>alphaketogluctarate

A

Isocitrate dehydrogenase

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41
Q

Alphaketoglutarate–>succinyl-coA

A

alpha ketoglutarate dehydrogenase.

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42
Q

Krebs pneumonic and what it generates for each acetyl coA

A

3 NADH, 1 FADH2, 2 CO2, 1 GTP “Citrate Is Krebs Starting Substrate For Making Oxaloacetate”

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43
Q

Complex 4

A

cytochrome c oxidsase

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44
Q

Complex 3

A

Coenzyme q

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45
Q

Complex 2

A

succinate dehydrogeniase

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46
Q

Block complex I

A

Rotenone

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47
Q

Bock complex III (coenzyme q)

A

Antimycin A

48
Q

Block complex IV (cytochrome c oxidase)

A

Cyanide, CO

49
Q

Block complex V (ATP synthase)

A

Oligomycin

50
Q

Uncoupling agents

A

2,4 dinitrophenol, aspirin, thermogenin in brown fat (produces heat)

51
Q

Glucocorticoids are potent stimulators of gluconeogenesis and specifically increase what two enzymes

A

Phosphoenol pyruvate carboxykinase and glucose 6 phosphatase

52
Q

Difference between odd chain fatty acids and even chain fatty acids in glucose source?

A

Odd chain fatty acids can be converted to propionyl CoA during metabolism, which can enter the TCA cycle (as succinyl-coA) and undergo gluconeogenesis, and serve as glucose source

Even chain fatty acids cannoot produce new glucose, since they yield only acetyl-CoA equivalents.

53
Q

Predominant source of carbon atoms for glucose synthesis during gluconeogenesis?

A

Lactate

54
Q

What is pyruvate derived from in gluconeogenesis?

A

Lactate, glycerol, glucogenic AA (eg. alanine)

55
Q

HMP shunt main job

A

Provide NADPH

56
Q

Oxidative HMP shunt pathway

A

Glucose 6-phosphate–>Ribulose 5 phosphate, 2 NADPH, CO2 via Glucose 6 phosphate dehydrogenase

57
Q

Non-oxidative HMP shunt pathway

A

Ribulose5-PhosphateRibose 5 phosphate, Glyceraldehyde 3 phosphate, Fructose 6 phosphate via transketolases and phosphopentose isomerase

58
Q

Oxidizing agents that can percipitate G6PD deficiency?

A

“Spleen Purges Nasty Inclusions From Damaged Cells”->Sulfonamides, Primaquine, Nitrofurantoin, Isoniazid, Fava Beans, Dapsone, Chloroquine

59
Q

With fructokinase deficiency, what is primary method of metabolism of fructose to fructose 6-phosphate?

A

Hexokinase

60
Q

Urine dipstick tests for what sugar in blood?

A

Glucose only!!

61
Q

Why do symptoms arise in fructose intolerance?

A

fructose 1-p is trapped and usage of all fructose prevents glycogenolysis and gluconeogenesis causing hypoglycemia. Also see jaundice, cirrhosis (hepatocellular manifestations)

62
Q

Alcohol counterpart of glucose?

A

Sorbitol (converted from glucose via aldose reductose)

63
Q

Tissues with aldose reductase and sorbitol dehydrogenase

A

Liver, ovaries, seminal vesicles, very low levels of sorbitol dehydrogense in lens

64
Q

Tissues with aldose reductase only

A

Schwann cells, kidney, retina

65
Q

Essential amino acids (need to be supplied in diet)

A

“PVT TIM HALL” Phenylalanine, Valine, Threonine, Tryoptophan,, Isoleucine, Methionine, Histidine, Arginine (considered essential for children because needed during periods of growth), Lysine, Leucine

66
Q

Acidic AA (negatively charged at body pH)

A

Aspartic acid (ie. aspartate) , glutamic acid (ie glutamate)

67
Q

Basic AA

A

Arginine (most basic), Lysine, Histidine

68
Q

pH>pKa

A

protons dissociate from amino acids

69
Q

pH

A

proton associate to group on amino acids

70
Q

Lactase deficiency stool and breath tests?

A

decrease pH stool and increase hydrogen content in breath

71
Q

Two AA required during periods of growth

A

Arginine and histidine

72
Q

Urea’s nitrogen is derived from what?

A

Aspartate and NH3

73
Q

Urea cycle pneumonic

A

Ordinarily, Careless Crappers Are Also Frivilous About Urination

74
Q

Two major carriers of nitrogen from tissues?

A

Alanine and glutamine

75
Q

Acidify GI tract and trap NH4+ for excretion

A

Lactulose

76
Q

Decrease colonic ammoniagenic bacteria

A

Rifaximin

77
Q

(Both of these bind AA and lead to excretion) may be given to decrease ammonia levels

A

Benzoate or Phenylbutyrate

78
Q

Ornithine transcarbamylase deficiency

A

X-linked recessive (vs other urea cycle deficiencies, that are auto recessive)

79
Q

Cofactor used in hydroxylase enzymes in synthesis of tyrosine, DOPA, serotonin, NO

A

BH4

80
Q

Phenylalanine and derivatives

A

Phe–>Tyrosine (converted to thyroxine)–>DOPA (which is converted to melanin)–>Dopamine–>Epi–>NE

81
Q

Tryptophan and derivatives

A

Serotonin, Niacin

82
Q

Histidine and derivative

A

Histamine

83
Q

Glutamate and derivitives

A

GABA and Glutathione

84
Q

Glycine and deriviatives

A

Porphyrin–>Heme

85
Q

Arginine and derivitives

A

NO, Urea, Creatinine

86
Q

PKU mutated enzyme

A

Phenylalanine hydroxylase

87
Q

MSUD mutated enzyme

A

alphaketoacid dehydrogenase

88
Q

Mutated enzyme albinism

A

tyrosinase

89
Q

mutated enzyme alkaptonuria

A

Homogentisate oxidase

90
Q

NE and dopamine is produced by _____, while epinephrine is only produced by _______

A

CNS and ANS, adrenal gland

91
Q

First step in catecholamine synthesis in adrenal medulla:

A

Tyrosine–>DOPA via tyrosine hydroxylase

92
Q

Failure to absorb what AA in cystinuria

A

Cysteine, ornithine, lysine, arginine (COLA)

93
Q

alpha 1,4 glycosidic linkage to glycogen chain is broken down to?

A

Glucose 1-P via glycogen phosphorylase

94
Q

alpha 1,6 glycosidic linkage is borken down to?

A

glucose via alpha 1,6 glucosidase

95
Q

Glycogen–>Glucose 1-Phosphate

A

Glycogen phosphorylase

96
Q

Glucose 1-Phosphate–>Glucose 6-phosphate

A

Phosphoglucomutase

97
Q

Glucose 6-Phosphate–>Glucose

A

Glucose 6-phosphatase (only in liver)

98
Q

alpha 1,6 glucosidase function?

A

alpha 1,6 glycosidic linkage –>glucose

99
Q

Von Gierke deficiency+treatment
Pompe deficiency
Cori dificiency
McArdle deficiency

A

Glucose-6-Phosphatase, glucose/cornstarch at night; avoidance of fructose+galactose
Lysosomal alpha 1,4 glucosidase (acid maltase)
Debranching enzyme (alpha 1,6-glucosidase)
Skeletal muscle Glycogen phosphorylase (myophosphorylase), Treat w/ vitamin B6 (cofactor)

100
Q

Fabry disease
Symptoms
Deficient enzyme?
Accumulated substrate?

A

Symptoms: Peripheral neuropathy of hands/feet, angiokeratomas, cardiovascular/renal disease
alpha-galactosidase A
Ceramide trihexoside

101
Q

Gaucher disease
Symptoms
Deficient enzyme?
Accumulated substrate?

A

Symptoms: Hepatosplenomegaly, pancytopenia, osteoporosis, aseptic necrosis of femur, bone crises, Gaucher cells,
Glucocerebrosidase (B-glucosidase)
Glucocerebroside

102
Q

Niemann-Pick
Symptoms
Deficient enzyme?
Accumulated substrate?

A

Progressive neurodegeneration, hepatosplenomegaly, foam cells (lipid-laden macrophages), “cherry-red” spot on macula
Sphingomyelinase
Sphingomyelin

103
Q

Tay-sachs disease
Symptoms
Deficient enzyme
accumulated substrate

A

Progressive neurodegneration, no hepatosplenomegaly, developmental delay, “cherry-red” spot on macula, lysososmes with onion skin
B-hexosaminidase A
GM2 ganglioside

104
Q

Krabbe disease
Symptoms
Deficient enzyme
accumulated substrate

A

Peripheral neuropathy, developmental delay, optic atrophy, globoid cells
Galactocerebrosidase
Galactocerebroside
Psychosine

105
Q

Metachromatic leukodystrophy
Symptoms
Deficient enzyme
Accumulated substrate

A

Central and peripheral demyelination with ataxia, dementia
Arylsulfatase A
Cerebroside sulfate

106
Q

Hurler syndrome
Symptoms
Deficient enzyme
Accumulated substrate

A

Developmental delay, gargoylism, airway obstruction, corneal clouding, hepatosplenomegaly
Alpha-l-iduronidase
Heparan sulfate, dermatan sulfate

107
Q

Hunter syndrome
Symptoms
Deficient enzyme
accumulated substrate

A

Mild hurler +aggressive behavior, NO corneal clouding
Iduronate sulfatase
Heparan sulfate, dermatan sulfate

108
Q

Rate limiting enzyme in fatty acid synthesis

A

acetyl coA carboxylase

109
Q

Rate limiting enzyme in LCFA degradation

A

Carnitine acyltransferase I

110
Q

Predominant location of fatty acid synthesis

A

liver, lactating mammary glands, adipose tissue

111
Q

What is the difference in odd chain fatty acid and even chain fatty acid production?

A

Odd chain fatty acids yield 1 propionyl coA which enter TCA cycle as succinyl coA, undergo gluconeogenesis and serve as glucose source

Even chain fatty acids cannot produce new glucose, since they yield only acetyl-coA equivalents

112
Q

What is the only TAG component from odd chain FFA that contributes to gluconeogenesis?

A

propionyl-coA

113
Q

Only organ that can use glycerol for energy

A

liver

114
Q

Type I hyperchylomicronemia deficiency

A

lipoprotein lipase deficiency or altered apolipoprotein CII

115
Q

Type IIa familial hypercholesterolemia deficiency

A

LDL receptor deficiency

116
Q

Type IV hypertriglyceridemia deficiency

A

Hepatic overproduction of VLDL

USMLE Step 1-2015 (18 decks)

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