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Step Nuggets > Biochem > Flashcards

Biochem Flashcards

1
Q

AAs in histones

A

Lysine and arginine, positively charged to hold DNA

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2
Q

Histone Structure

A

H2A, H2B, H3, H4 (2ea) form the histone - 10nm fiber
Recall the 10nm fiber is vulnerable to endonucleases
H1s condense to 30nm

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3
Q

Name the purines

A

A, G

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4
Q

Name the pyrimidines

A

C,U,T

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5
Q

Lesch-Nyhan Syndrome

A

Defective purine salvage due to absent HGPRT
Build up of uric acid
XLR
Intellectual Disability, self-mutilation, aggression, hyperurecemia, gout, dystonia

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6
Q

HGPRT Function

A

Converts hypoxanthine to IMP, Guanine to GMP

Purine Salvage pathway

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7
Q

Defect of nucleotide excision repair

A

Xeroderma pigmentosum

no repair of pyrimidine dimers due to UV light

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8
Q

Defect of DNA mismatch repair

A

HNPCC - Chr5

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9
Q

Defect in phosphotranferase -> failure of Golgi to phosphorylate mannose residues

A

I-cell disease
Proteins are secreted rather than targeted to the lysosome
Course facial features, clouded corneas, restricted joint movement, high plasma lysosomal enzymes
Fatal in childhood

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10
Q

ADPKD

A

Bilateral, massive enlargement of the kidneys due to multiple large cysts
AD
85% mutation in PKD1 - Chr16
15% mutation in PKD2 - Chr4

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11
Q

Familial Adenomatous Polyposis

A

Colon has 1000’s of polyps -> 100% progression to colon cancer unless resected
AD
Chr5

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12
Q

Familial Hypercholesterolemia

A

Elevated LDL b/c absent LDL receptors -> severe atherosclerosis in early life, tendonous xanthomas
AD

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13
Q

Hereditary spherocytosis

A

Spheroid RBCs due to absent ankyrin or spectrin -> hemolytic anemia
AD
Treatment: splenectomy

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14
Q

Marfan Syndrome

A

Fibrillin-1 mutation -> connective tissue disorder
tall w/ long extremities, hypermobile joints, cystic medial necrosis of the aorta, dissections, floppy valves, lens subluxations
AD

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15
Q

NF1

A

Chr17
cafe-au-lait, cutaneous neurofibromas
AD, variable expression

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16
Q

NF2

A

Chr22
bilateral acoustic schwannomas, juvenile cataracts, meningiomas, ependymomas
AD, variable expression

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17
Q

von Hippel-Lindau

A

Multiple tumors, benign and malignant
VHL gene on Chr3
AD

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18
Q

Fragile X Syndrome

A

Defect in methylation and expression of FMR1 gene due to CGG repeats on X
2nd most common cause of genetic intellectual disability
enlarged testes, long face w/ large jaw, large ears, autism,
mitral valve prolapse

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19
Q

Trisomy 21

A

Down Syndrome
Flat facies, epicanthal folds, single palmar crease, gap between toes, duodenal atresia, Hirschsprung’s, ostium primum ASDs, ALL, Alzhiemer’s
Most cases due to meiotic non-disjunctions

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20
Q

Trisomy 18

A

Edwards Syndrome

severe intellectual disability, rocker bottom feet, low set ears, clenched hands

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21
Q

Trisomy 13

A

Patau Syndrome

severe intellectual disability, rocker bottom feet, cleft lip/palate, polydactyly

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22
Q

Biochemical action of Glucagon

A

Phosphorylate Stuff!!! through PKA on Ser, Thr

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23
Q

Biochemical action of Insulin

A

Dephosphorylate stuff!!! TK receptors

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24
Q

TLCFN

A 
Cofactors required by PDH and alpha-ketoglutarateDH
Thiamine (B1)
Lipoic Acid
CoA (pantothenate/B5)
Flavin (Riboflavin/B2)
NAD (Niacin, B3)
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25
Q

Inputs to TCA Cycle

A

1 Acetyl CoA
3 NAD+
1 FAD+
1 GDP

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26
Q

Outputs of TCA Cycle

A

2 CO2
3 NADH
1 FADH2
1 GTP

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27
Q

Citrate Function, outside of TCA

A

used in FA synthesis, inhibits glycolysis

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28
Q

Succinyl-CoA Sources

A

VOMIT
Valine, Oddchain FA, Met, Iso, Thr
Requires B12
In excess energy states (high ATP), goes to heme synthesis

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29
Q

Required cofactor of transaminases?

A

B6 / pyridoxine

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30
Q

Malate shuttle

A

Used to get NADH into the mitochondria for ETC

Get 2.5-3 ATP per NADH (3 H+ pumps)

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31
Q

G3P shuttle

A

Used to get NADH into ETC via FADH2 (1.5-2 ATPs, uses 2 H+ pumps)

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32
Q

Rotenone

A

Blocks Complex 1 of ETC
Decreases proton gradient and ATP synthesis
Barbiturates also block Complex 1

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33
Q

Antimycin A

A

Inhibits Complex III of ETC

blocks ATP synthesis

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34
Q

Cyanine, CO

A

Block Complex IV of ETC
Decreased ATP synthesis
House fires, ‘almond breath’ for cyanide

35
Q

Oligomycin

A

Inhibits ATP synthase, F0 subunit (channel)

No ATP production

36
Q

Name some ETC uncoupling agents and explain the mechanism

A

2,4 DNP, high dose aspirin, thermogenin (in brown fat)

leaky membrane causes decreased H+ gradient and increased metabolism -> heat, increased O2 usage

37
Q

Sources of pyruvate for gluconeogenesis

A

Alanine via ALT [B6]
all aa’s except leucine and lysine can eventually make pyruvate
Lactate via LDH (uses NAD+, produces NADH)

DHAP can come from FA and make glucose also

38
Q

Name the enzymes unique to gluconeogenesis

A

Pyruvate carboxylase: in mito, pyr -> OAA
PEP carboxylase: in cyto, OAA -> PEP (induced by cortisol, leading to hyperglycemia in Cushing’s)
F1,6bisphosphatase: cyto, inhibited by F2,6BP, F16BP->F6P
G6phosphatase: cyto, G6P -> glucose, only in the liver

39
Q

Aldolase B Deficiency

A

Fructose intolerance, AR
accumulation of F6P, causing a decrease in available phosphate -> inhibition of glycogenolysis and gluconeogenesis
hypoglycemia, jaundice, cirrhosis, vomiting after ingestion of juice, fruit, honey…
‘reducing sugar in the urine’- non-specific
Tx; avoid fructose and sucrose in the diet

40
Q

Galactokinase Deficiency

A

Relatively mild, AR
Build up of Galactitol (via aldose reductase) -> infantile cataracts, failure to track, failure to develop social smile, galactose in blood and urine

41
Q

Galactose-1-phosphate uridyltransferase deficiency

A

Classic Galactosemia, AR
accumulation of back-products (Galactitol) causes damage
FtT, jaundine, hepatomegaly, infantile cataracts, intellecetual disability
associated with Ecoli sepsis in neonates

42
Q

Glucose-6-Phosphatase deficiency

A

Von Gierke’s, AR
severe fasting hypoglycemia, excess glycogen in liver (megaly), lactic acidosis
Normal glycogen
Tx: frequent oral glucose/cornstarch

43
Q

Lysosomal alpha1,4-glucosidase (acid maltase) deficiency

A

Pompe Disease, AR
cardiomyopathy and systemic findings lead to early death
normal glycogen
Tx: ERT

44
Q

Debranching enzyme (alpha16glusidase) deficiency

A

Cori Disease, AR
Mild hypoglycemia, nml blood lactate
short (1 residue) branches in glycogen

45
Q

Skeletal muscle glycogen phosphorylase deficiency

A

McArdle Disease, AR
increased glycogen in muscle, but can’t break it down
painful muscle cramps, myoglobinuria

46
Q

What are the essential FAs?

A

Linoleic (w6) and Linolenic (3) acids

Linoleic is the precursor to arachidonic acid (w6)

47
Q

ApoE

A

Mediates remnant uptake by the liver

donated to VLDL, chylomicron by HDL

48
Q

ApoA1

A

Activates LCAT, allows HDL to pick up peripheral cholesterol

49
Q

ApoCII

A

Activates lipoprotein lipase

donated to VLDL, chylomicron from HDL

50
Q

ApoB48

A

In chylomicrons from the gut

51
Q

ApoB100

A

Binds LDL receptors

52
Q

Chylomicrons

A

ApoB48. Gets E and CII from HDL; E allows uptake by the liver and CII activates LPL for TGs drop-off. Delivers dietary TGs to peripheral tissues, then (as a chylo remnant) delivers cholesterol to the liver

53
Q

VLDL

A

ApoB100. Gets E and CII from HDL; E allows uptake by the liver and CII activates LPL for TGs drop-off. Delivers hepatic TGs to peripheral tissues.

54
Q

IDL

A

Formed from degradation of VLDL (by LPL). Can deliver TGs and cholesterol to the liver or progress to LDL.

55
Q

LDL

A

Delivers hepatic cholesterol to peripheral tissues. Formed from IDL via hepatic lipase (HL). ApoB100.

56
Q

HDL

A

Picks up peripheral cholesterol (in vessels) and returns to the liver. Donates CII and E to chylo’s and VLDL.

57
Q

Effects of increased liver cholesterol

A

downregulates LDL receptors leading to increased LDL in the blood
Statins work by decreasing denovo synthesis of liver cholesterol, thus increasing the number of LDL receptors and clearing LDL from the blood

58
Q

Fatty Streak Formation Basics

A

LDL + O2 (oxidized) -> cholesterol deposits in the vessels
enhanced by O2 and turbulence: arteries > veins
also enhanced by gravity: AA at the iliac bifurcation

59
Q

Smith-Lemli-Optiz Syndrome (SLO)

A

Mutation in DHCR7 (last step in cholesterol synthesis)
decreased cholesterol for development -> FtT, int. disability, decreased steroid hormones, problems with myelination, problems with SSH processing
Tx: high dietary cholesterol and HMG-CoA reductase inhibitors

60
Q

Type I Familial Dyslipidemia - Hyperchylomicronemia

A

AR LPL or CII deficiency -> increased chylo’s, TGs in the blood; saturated excretion via bile leads to gallstones and recurrent pancreatitis; xanthomas

61
Q

Type II Familial Dyslipidemia - Famial Hypercholesterolemia

A

AD absent or defective LDL receptors

accelerated atherosclerosis, tendon xanthomas, corneal arcus

62
Q

Abetalipoproteinemia

A

no ApoB100 or ApoB48
cant absorb dietary fat: DKEA deficiencies (poor night vision, acanthocytes), steatorhea, no lineoleic acid -> no arachodonic acid products
markedly decreased TGs and cholesterol

63
Q

Name the amino acids which are strictly ketogenic

A

leucine and lysine

64
Q

Name the amino acids which can be glucogenic or ketogenic

A

Tyr, Trp, Phe, Ile, Thr

65
Q

Symptoms of hyperammonemia?

A

asterixis tremor, CNS/ mental status changes, blurred vision

66
Q

Increased orotic acid in the urine, decreased BUN, hyperammonemia

A

Ornithine transcarbamylase deficiency
ornithine + carbamoyl phosphate -> citrulline in the urea cycle
buildup of carbamoyl phasphate leads to increased orotic acid

67
Q

Derivatives of Phenylalanine

A

Tyrosine –> Thyroxine
Tyrosine -> dopa -> melanin and dopamine
dopamine -> NE and epi

68
Q

Derivatives of Tryptophan

A

Niacin -> NAD/NADP

Serotonin -> Melatonin

69
Q

Peripheral burning neuropathy, angiokeratomas, CV/renal disease

A

Fabry’s; XLR

deficient in alpha-galactosidase A, build up of ceramide trihexoside

70
Q

Bone marrow issues causing fractures and pancytopenia, hepatosplenomegaly

A

Gaucher Disease, AR
Deficient in glucocerebrosidase (beta-glucosidase)
Build up of Glucocerebroside

71
Q

Neurodegeneration, cherry red spot on the macula, with hepatosplenomegaly

A

Niemann-Pick Disease, AR
Deficient in Sphingomylinase
Build up of sphingomyelin

72
Q

Neurodegeneration, developmental delay, cherry red spot on the macula without hepatosplenomegaly

A

Tay-Sachs, AR in Ashkenazi Jews
Deficient in Hexosaminidase A
Build up of GM2 ganglioside

73
Q

Peripheral neuropathy with optic atrophy and globoid cells

A

Krabbe Disease, AR
deficiency of galactocerebrosidase
build up of galactocerebroside, psychosine

74
Q

central and peripheral demylination with ataxia and dementia

A

Metachromatic leukodystrophy, AR
Deficiency of arylsulfatase A
build up of cerebroside sulfate

75
Q

developmental delay, gargoylism, airway obstruction, corneal clouding and hepatosplenomegaly

A

Hurler syndrome
deficiency of alpha-L-iduronidase
build up of heparan sulfate and dermatan sulfate

76
Q

mild Hurler symptoms with aggressive behavior, no clouding

A

Hunter syndrome ‘hunters need to see’
deficiency of iduronate sulfatase
build up of heparan sulfate and dermatan sulfate

77
Q

alpha-galactosidase A deficiency

A

Fabry’s; ceramide trihexoside

78
Q

glucocerebrosidase (beta-glucosidase) deficiency

A

Gaucher’s Disease; glucerebroside

79
Q

sphingomyelinase deficiency

A

Niemann-Pick; sphingomyelin

80
Q

hexosaminidase A deficiency

A

Tay-Sachs; GM2 ganglioside

81
Q

galactocerebrosidase deficiency

A

Krabbe; galactocerebroside, psychosine

82
Q

arylsulfatase A deficiency

A

Metachromatic leukodystrophy; cerebroside sulfate

83
Q

alpha-L-iduronidase deficiency

A

Hurler; heparan sulfate, dermatan sulfate

84
Q

iduronate sulfatase deficiency

A

Hunter; heparan sulfate, dermatan sulfate

Step Nuggets (23 decks)

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