Biochemistry Metabolism Flashcards Preview

USMLE Step 1 > Biochemistry Metabolism > Flashcards

Flashcards in Biochemistry Metabolism Deck (135):
1

What processes occur in mitochondria?

Fatty acid oxidation (Beta oxidation), acetyl CoA production, TCA cycle, oxidative phosphorylation

2

What processes occur in cytoplasm?

glycolysis, FA synthesis, HMP shunt, protein synthesis (RER), steroid synthesis (SER), cholesterol synthesis

3

What processes require both cytoplasm and mitochondria:

HUG: heme synthesis, urea cycle, gluconeogenesis

4

kinase

uses ATP to add high energy phosphate

5

phosphorylase

adds inorganic phosphate w/out using ATP

6

phosphatase

removes phosphate group

7

dehydrogenase

catalyzes ox-redox reactions

8

hydroxylase

adds -OH group onto substrate

9

carboxylase

transfers CO2 group with help of biotin

10

mutase

relocates functional group within molecule

11

RDS: glycolysis

PFK-1; +: AMP, F26BP; -: ATP, citrate

12

RDS: gluconeogenesis

F16BPhosphatase; + ATP, acetyl-CoA; - AMP F26BP

13

RDS: TCA cycle

isocitrate dehydrogenase; + ADP; - ATP, NADH

14

RDS: glycogenesis

glycogen synthase; + G6P insulin, cortisol; - epinephrine, glucagon

15

RDS: glycogenolysis

glycogen phosphorylase; + epinephrine, glucagon, AMP; - G6P, insulin ATP

16

RDS: HMP shunt

G6PD; + NADP, - NADPH

17

RDS: de novo pyrimidine synthesis

Carbamoyl phosphate synthetase II

18

RDS: do novo purine synthesis

Glutamine-PRPP amidotransferase: -AMP, IMP, GMP

19

RDS: urea cycle

carbamoyl phosphate synthetase I: + n acetyl glutamate

20

RDS: fatty acid synthesis

acetyl-coa carboxlyase: + insulin, citrate; - glucagon, palmitoyl coA

21

RDS: fatty acid oxidation

carnitine acyltransferase: - malonyl coA

22

RDS: ketogenesis

HMG-coa synthase

23

RDS: cholesterol synthesis

HMG coA reductase: + insulin, thyroxin, - glucagon, cholesterol

24

which enzymes require biotin as a cofactor?

pyruvate carboxylase (pyruvate to OAA); acetyl coA to malonyl coA; propionyl COA to methylmalonyl COA

25

which enzymes require thiamine?

Transketolase (ribulose 5 phosphate to F6P); pyruvate DH (pyruvate to acetyl CoA); a-ketoglutarate DH (alphaKG to succinyl coA)

26

where is NADPH made? used?

product of HMP shunt; used in anabolic processes, respiratory burst, CYP450 system, glutathione reductase

27

hexokinase vs glucokinase

hexokinase in most tissues except liver/B cells of pancreas; low Km; high affinity; low Vmax and capacity; not induced by insulin; feedback inhibited by G6P; not associated with mature onset diabetes; glucokinase is opposite of hexokinase

28

galactokinase

galactose to galactose 1 phosphate; mild galactosemia

29

galactose 1 phophate uridyltransferase

glactose 1 phosphate to glucose 1 phosphate; severe galactosemia

30

aldolase A vs B

aldolase A--muscle, B--liver; glyceraldehyde 3 phosphate/DHAP to fructose 1,6 bisphosphate

31

hexokinase/glucokinase

Glucose to glucose 6 phosphate; irreversible

32

Glucose 6 phosphatase

glucose 6 phosphate to glucose; irreversible; von Gierke's

33

G6PD

glucose 6 phosphate to 6 phosphogluconolactone; irreversible

34

transketolase

ribulose 5 phosphate to fructose 6 phosphate; requires thiamine

35

PFK-1

fructose 6 phosphate to F16BP; irreversible

36

Fructose 1,6 bisphosphatase

F16BP to F6P; irreversible

37

fructokinase

fructose to F1P; essential fructosuria

38

aldolase B

F1P to DHAP/glyceradehyde, fructose intolerance

39

pyruvate kinase

PEP to pyruvate; irreversible

40

pyruvate DH

pyruvate to acetyl coA; requires thiamine; irreversible

41

HMG coA reductase

HMG coA to mevalonate

42

pyruvate carboxylase

pyruvate to OAA; irreversible, requires biotin

43

PEP carboxykinase

OAA to PEP; irreversible

44

citrate synthase

OAA to citrate;

45

isocitrate dehydrogenase

isocitrate to alpha ketoglutarate; irreversible

46

alpha KG DH

a KG to succinyl coA; irreversible, requires thiamine

47

ornithine transcarbamoylase

ornithine + carbamoyl phosphate to citrulline

48

Which reactions in glycolysis produce ATP?

phosphoglycerate kinase (13BPG to 3 PG, reversible); pyruvate kinase (PEP to pyruvate, irreversible)

49

fasting state regulation by F26BP

increased glucagon-->increased cAMP-->increased protein kinase A-->increased FBPase2, decreased PFK2, less glycolysis

50

fed state regulation by F26BP

increased insulin-->decreased cAMP-->decreased PKA-->decreased FBPase2, increased PFK2, more glycolysis, less gluconeogenesis

51

pyruvate dehydrogenase complex requires which cofactors:

pyrophosphate (B1, thiamine, TPP); FAD (B2, riboflavin); NAD (B3, niacin); CoA (B5, pantothenate); lipoic acid

52

vomiting, rice water stools, garlic breath

arsenic poisoning, inhibits lipoic acid, disrupts pyruvate DH complex

53

purely ketogenic AAs

lysine, leucine

54

neurologic deficits, lactic acidosis, increased serum alanine since infancy

pyruvate dehydronase complex deficiency; buildup of pyruvate that gets shunted to lactate (via LDH) and alanine (via ALT); Tx with high intake of ketogenic nutrients

55

pyruvate can be shunted to 4 different pathways:

alanine amiotransferase (ALT) to alanine (requires B6); pyruvate carboxylase (requires biotin) to OAA (replenish TCA cycle or be used in gluconeogenesis); pyruvate DH (connect glycolysis to TCA cycle); LDH (requires B3)

56

Rotenone

inhibits Complex I of ETC

57

succinate dehydrogenase

part of TCA and Complex II of ETC

58

Antimycin A

inhibits Complex III of ETC

59

Cyanide, CO

inhibits complex IV of ETC

60

oligomycin

inhibits complex V of ETC (ATP synthase)

61

contains CoQ and cytochrome C

Complex III of ETC

62

reduces oxygen to water in ETC

complex IV

63

which side of mt membrane is proton gradient formed on?

proton gradient is formed in intermembrane space and flows through complex V on inner mt membrane to the mitochondrial matrix

64

2,4 dinitrophenyl

increase permability of membrane; uncouple ETC, produces heat

65

what are uncoupling agents?

2,4 dinitrophenyl, aspirin (fevers after OD), thermogenin in brown fat

66

what reaction in gluconeogenesis requires GTP?

PEP carboxykinase (OAA to PEP)

67

odd chain vs even chain fatty acids in gluconeogenesis

only odd chain fatty acids can participate; converted to proprionyl CoA and enter TCA as succinyl cOA; even chain FAs yield only acetyl CoA

68

patients with CGD are at risk for what types of infection?

catalase + bugs: aspergillus, S aureus

69

pyocyanin

released by pseudomonas aeruginosa to generate ROS to kill competing bacteria

70

lactoferrin

protein found in secretory fluid and neutrophils that inhibits bacterial growth via iron chelation

71

failure to track objects or develop a social smile

galactokinase deficiency; galactitol accumulates in lens--infantile cataracts

72

failure to thrive,jaundice, hepatomegaly, infantile cataracts, retardation

classic galactosemia, uridyltransferase deficiency; tx by excluding galactose and lactose

73

Schwann cells, retina, and kidneys lack what enzyme that makes them prone to damage by hyperglycemia

they have aldose reductase but lack sorbitol dehydrogenase, which results in accumulation of sorbitol->osmotic damage

74

glucogenic essential amino acids:

methionine, valine, histidine

75

glucogenic/ketogenic essential amino acids

isoleucine, phenylalanine, threonine, tryptophan

76

Ketogenic essential amino acids

lysine, leucine

77

which step of urea cycle requires N-acetyl glutamate as cofactor?

carbamoyl phosphate synthetase I (CO2 + NH3 to carbamoyl phosphate) requires 2 ATP; occurs in mitchondria

78

which step of urea cycle generates AMP?

argininosuccinate synthetase: citrulline + aspartate to argininosuccinate requires ATP and generates AMP

79

which step of urea cycle generates fumarate?

argininosuccinase: argininosuccinate to arginine generates fumarate

80

which step of urea cycle generates urea?

arginase: arginine + H2O to ornithine and urea (to kidney)

81

urea is comprised of what three things?

ammonia; carbon dioxide; aspartate; NH2-C=O-NH2

82

ammonia is transported from muscle to liver how?

amino acids to glutamate to alanine-->bloodstream-->liver-->glutamate-->urea; pyruvate + NH3 = alanine; alpha KG + NH3 = glutamate

83

urea cycle occurs mostly in?

liver; impaired in liver disease

84

N-acetyl glutamate deficiency vs carbamoyl phosphate synthetase deficiency

NAG deficiency is AR, CPS is X linked recessive; both present identically: early in life, orotic acid elevated in blood and urine; decreased urea production; hyperammonemia; no megaloblastic anemia; increased ornithine with normal urea cycle enzymes suggests NAG deficiency

85

carbamoyl phosphate synthetase deficiency vs orotic aciduria

orotic aciduria: UMP synthase (orotic acid to UMP) deficiency (de novo pyrimidine synthesis); no hyperammonemia; megaloblastic anemia

86

Catecholamine synthesis pathway:

Phe-->Tyrosine-->Dopa-->Dopamine-->NE-->Epi-; cofactors required in order: BH4, BH4, B6, vitC, SAM; Enzymes: phenylalanine hydroxylase, tyrosine hydroxylase, dopa decarboxylase, dopamine hydroxlyase,

87

Tyrosine can form what three products:

Dopa or Thyroxine, homogentisic acid

88

DOPA can form what two products:

Melanin or Dopamine

89

tryptophan forms which AAs

niacin (requires B6) to NAD/NADP+, serotonin (requires BH4 and B6); serotonin to melatonin

90

histidine forms which AAs

histamine (requires B6)

91

Glycine forms which amino acids

porphyrin (requires B6)-->Heme

92

Glutamate forms which amino acids

GABA (requires B6); glutathione

93

Arginine forms which AAs

creatine, urea, Nitric oxide (requires BH4)

94

Phenlyketonuria can be caused by:

deficiency in phenylalanine hydroxylate or BH4 (malignant PKU); Tx by reducing Phe intake and increased tyrosine intake

95

maternal PKU

infant microcephaly, intellectual deficiency, growth retardation, congenital heart defect

96

alkaptonuria

AR deficiency of homogentisate oxidate in degradative pathway of tyrosine to fumarate

97

dark connective tissue, brown sclerae, urine turns black on prolonged air, may have debilitating arthralgias

alkaptonuria--homogentisate oxidate deficiency; AR; homogentisate acid buildup in cartilage

98

albinism

tyrosinase deficiency--cannot convert DOPA to melanin

99

inhibits DOPA decarboxylase

carbidopa

100

3 deficiencies resulting in homocystinuria

cystathione synthase deficiency (Tx by decreasing methionine, increasing cysteine, increase B12 and folate in diet); decreased affinity of cystathione synthase for pyridoxal phosphate (increase B6 and cysteine in diet); Homocystein methyltransferase deficiency (increase methionine in diet)

101

homocystinuria vs marfans?

marfans has negative nitroprusside test. lens up and out in marfans; homocystinuira lens down and in;

102

cystinuria

defect of renal PCT COLA transporter (cysteine, ornithine, lysine, arginine); excess cystine in urine-->hexagonal uric acid stones; AR; nitroprusside test positive; Tx with urinary alkalinization (potassium citrate, acetazolamide) and chelating agents, hydration

103

urine smells like burnt sugar

MSUD: blocked degradation of ILV (isoleucine, leucine, valine) due to decreased alpha-ketoacid dehydrogenase (B1); Tx AA restriction with B1 supplementation;

104

Glycogen phosphorylase vs glycogen synthase

phosphorylase (glycogen to glucose) is activated by glycogen phosphorylase kinase (via glucagon, epinephine and PKA and calcium); synthase (glucose to glycogen) is activated by insulin; PKA inhibits synthase; protein phosphatase inhibits phosphorylase

105

severe fasting hypoglycemia, increased glycogen in liver, high blood lactate, hepatomegaly

Type I glycogen storage disease (von Gierke); glucose 6 phosphatase defect-->cant release glucose from liver into bloodstream; tx with frequent carbs, avoid fructose and galactose (both are converted to glucose 6 P)

106

cardiomyopathy and systemic findings-->early death

Type 2 GSD (Pompe disease); lysosomal alpha 1,4 glucosidase (acid maltase) deficiency;

107

milder hypoglycemia, normal blood lactate levels

Type 3 (Cori disease); debranching enzyme (alpha 1,6 glucosidase); intact gluconeogenesis just can't utilize all of glycogen

108

increased glycogen in muscle, painful muscle cramps, myoglobinuria (red urine) with strenous exercise, arhythmia from electrolyte disturbances

Type V (McArdle disease); skeletal muscle glycogen phosphorylase (myophosphorylase); can't break down glycogen in muscle

109

all glycogen storage disease are inherited in what fashion?

AR

110

peripheral neuropathy of hands/feet, angiokeratomas, cardiovascular/renal disease

Fabry disease; alpha galactosidase A, accumulation of ceramide trihexoside; XR

111

HSM, pancytopenia, aseptic necrosis of femur/bone crises, lipid laden macrophages,

Gaucher disease, glucocerebrosidase (beta glucosidas), accumulation of glucocerebroside, AR

112

progressive neurodegeneration, HSM, cherry red spot on macula, foam cells (lipid laden macrophages)

Niemann Pick disease; sphingomyelinase; accumuation of sphingomyelin, AR

113

progressive neurodegeneration, developmental delay, cherry red spot on macula, lysosome with onion skin, no HSM

Tay Sachs, hexosaminidase A, GM2 ganglioside accumulation, AR

114

Peripheral neuropathy, developmental delay, optic atrophy, globoid (multinucleated) cells

Krabbe disease, Beta galactosidase (galactocerebrosidase); galactocerebroside/psychosine; AR

115

central and peripheral demyelination with ataxia, dementia

metachromatic leukodystrophy; arylsulfatase A; cerebroside sulfate, AR

116

developmental delay, gargolyism, airway obstruction, corneal clouding, HSM

Hurler syndrome; alpha L iduronidase; heparan sulfate, dermatan sulfate, AR

117

Mild hurler + aggressive behavior, no corneal clouding

Hunter Syndrome; iduronate sulfatase; heparan sulfate/dermatan sulfate; XR

118

Which sphingolipidoses LSD is XR?

Fabry's all others are AR

119

Which mucopolysaccharidoses is XR?

hunter's; hurlers is AR

120

weakness, hypotonia, hypoketotic hypoglycemia

carnitine deficiency (cannot transport LCFAs into mitochondria, toxic accumulation of FAs)

121

acyl-coA deficiency

increased dicarboxylic acids, decreased glucose and ketones, acetyl coA is + allosteric regulator of pyruvate carboxylase in gluconeogenesis; decreased acetyl CoA, decreased fasting glucose

122

ketone bodies

acetoacetate and B-hydroxybutyrate; urine test does not detect B hydroxybutyrate

123

ketone bodies cannot be utilized as fuel where?

liver (no thiotransferase); RBCs (no mitochondria); renal medulla (not enough oxidative capacity)

124

pancreatic lipase

degradation of dietary TGs in small intestine

125

lipoprotein lipase

degradation of TGs circulating in chylomicrons and VLDLs, found on vascular endothelial cell surface; activated by insulin

126

hepatic TG lipase

degradation of TG remaining in IDL

127

hormone sensitive lipase

degradation of TGs stored in adipocytes

128

LCAT

esterifies cholesterol (nascent HDL to mature HDL)

129

CETP

transfer of cholesterol esters from HDL to VLDL/IDL/LDL

130

chylomicrons vs VLDL

chylomicrons carry TGs from food to peripheral tissues. VLDL carries endogenous TGs from the liver; chylomicrons: ApoB48, VLDL ApoB100

131

lipoprotein lipase cofactor

ApoCII

132

mediates remnant uptake

ApoE

133

activates LCAT

Apo A-I

134

mediates chylomicron secretion

B-48

135

binds LDL receptor

B-100