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Biochemistry Flashcards

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1
Q

What 5 molecules are used to make purines?

A

Aspartate, glutamine, CO2, glycine, and THF

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2
Q

What 4 molecules are used to make pyrimidines?

A

Aspartate, glutamine, CO2, and ATP

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3
Q

In what order are the base, sugar-PRPP (ribose) assembled in:
Pyrimidines
Purines

A 
Pyrimidines = Base + sugar-PRPP
Purines = Sugar-PRPP + base
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4
Q

What is the rate-limiting step in pyrimidine and purine base synthesis?

A

Pyrimidine - CPS2

Purine - PRPP Synthetase

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5
Q

What is the mechanism of:
Hydroxyurea
5FU

A 
Hydroxyurea = inhibits ribonucleotide reductase
5FU = inhibits thymidylate synthase
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6
Q

Megaloblastic anemia that is not corrected with vitB12 and folate supplementation

A

Orotic aciduria

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7
Q

Increased orotic acid in urine + hyperammonemia

Increased orotic acid in urine without hyperammonemia

A

Ornithine transcarbamylase deficiency

Orotic aciduria

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8
Q

Treatment for orotic aciduria

A

Uridine supplementation (bypass UMP synthase)

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9
Q

What is the mechanism of mycophenylate?

A

Inhibits IMP DH

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10
Q

What is the inheritance pattern of Lesch-Nyhan syndrome?

A

X-linked recessive

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11
Q

What DNA polymerases are used in prokaryotes and what are their functions?

A 
DNApol1 = replaces primers
DNApol3 = leading and lagging strand
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12
Q

What DNA polymerases are used in eukaryotes and what are their functions?

A

a - lAgging strand (has it’s own primase)
B - Mismatch DNA repair
d - leaDing strand
gamma - mitochondrial DNA replication

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13
Q

When is mismatch repair needed?

What disease results from a defect?

A 
Wrong nucleotide is incorporated during replication
Lynch syndrome (hereditary non-polyposis colorectal cancer HNPCC)
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14
Q

When is nucleotide excision repair needed?

What disease results from a defect?

A

When DNA is damaged outside of replication and causes bulky kinks (UV radiation causes thymidine dimers)
Xeroderma pigmentosum

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15
Q

When is base excision repair needed?

What type of DNApol is used?

A

When DNA is damaged outside of replication where the composition of the base is change but the backbone remains intact (non-bulky damage)
DNApol B

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16
Q

What are the steps of:
Nucleotide excision repair
Base excision repair

A 
NER = endonuclease - DNApol - ligase
BER = glycosylase (removes base from the backbone) - endonuclease - DNApol - ligase
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17
Q

When is non homologous end joining repair needed?

What disease results from a defect?

A

dander breaks

Ataxia-telangectasia

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18
Q

What is Bloom syndrome?

How does it present?

A 
Defect in DNA helicase
Sunlight hypersensitivity (similar to XP)
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19
Q

IgA deficiency + poor smooth pursuit/ataxia + spider angiomas + elevated AFP

A

Ataxia-telangectasia

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20
Q

What RNA polymerases are used in eukaryotes and what are their functions?

A

RNApol 1 = rRNA
RNApol 2 = mRNA
RNA pol 3 = tRNA

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21
Q

How is the a-amanitin toxin from the Amanita phalloides mushroom toxic?

A

Inhibits RNApol2 which impairs mRNA synthesis

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22
Q

I cell disease

A

Phosphotransferase mutation - cannot put mannose-6 phosphate on lysosomal enzymes to direct them, so they are released into the interstitial by default

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23
Q

Prader-WIlli syndrome

A

Maternal gene normally silenced, but paternal gene is also deleted - over eating, intellectual disability, hypogonadism, short stature
“POP” - praderwilli, over eating, paternal deletion

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24
Q

Angelman syndrome

A

Paternal gene normally silenced, but maternal gene is also deleted - inappropriate laughter (happy puppet), ataxia, seizures, intellectual disability
“MAMA” - maternal deletion, angelman, mood (laughter), ataxia

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25
How do epinephrine (muscles) and glucagon (liver) raise blood sugar?
Bind GCPR (Gs type) - increase intracellular cAMP - activate protein kinase A - activate phosphorylase kinase: 1. Inhibits glycogen synthase 2. Activates glycogen phosphorylase
26
Hypoglycemia/hyperlipidemia + gout + elevated lactic acid + hepatosplenomegaly + enlarged kidneys
``` VonGierke disease (type 1) = glucose-6-phosphatase mutation Muscle doesn't release glucose into the blood, so this only affects liver (glycogenolysis and gluconeogenesis) ```
27
Hypoglycemia with normal lactic acid and uric acid + normal kidneys + hepatosplenomegaly + muscle weakness
Cori disease (type 3) = a-1,6-glucosidase mutation
28
Muscle cramps and myoglobinuria with strenuous exercise
McArdle disease (type 5) = glycogen phosphorylase
29
Where does glycogen accumulate in Pompe disease? | What organs are affected by infantile and adult type Pompe?
Lysosomes Infant - cardiomyopathy Adult - respiratory failure
30
What are the required co-factors for pyruvate DH?
B1 (thiamine), B2 (FAD), B3 (NAD), B5 (CoA), and lipoic acid
31
What 2 metabolites are elevated in pyruvate DH deficiency?
Lactic acid (lactic acid DH, pyruvate to lactic acid) and alanine (ALT, pyruvate to Ala)
32
What is the inheritance pattern for pyruvate DH deficiency? | How is it acquired?
``` X-linked Arsenic exposure (depletes lipoid acid and thiamine) ```
33
Treatment for pyruvate DH deficiency
Purely ketogenic protein and fat diet - Lysine and Leucine
34
``` What part of the electron transport chain is inhibited by: Rotenone (fish poison), MPTP/MPP Antimycin A (fish poison) CN, azide (N3-), CO, H2S Oligomycin (macrolide) ```
Complex 1 Complex 3 Complex 4 ATP synthase
35
What enzymes require Selenium?
Glutathione peroxidase and reductase
36
What enzyme is deficient in essential fructosuria?
Fructokinase
37
Hypoglycemia + hepatomegaly/jaundice
Fructose intolerance (fructose is trapped in the cells by phosphorylation, but cannot be utilized. Depleted PO4 shuts down gluconeogenesis and cannot correct hypoglycemia)
38
What enzyme is deficient in fructose intolerance? | What sugars must be avoided?
Aldolase B | Fructose or sucrose
39
Infantile cataracts and elevated galactose in urine/blood
Galactokinase deficiency - galactitol accumulates in the lens causing cataracts
40
Infantile cataracts + hepatomegaly/jaundice + intellectual disability
Classic galactosemia
41
What enzyme is deficient in classic galactosemia? | What sugars must be avoided?
Galactose-1-phosphate uridyltransferase | Galactose and lactose
42
How long is glycogenolysis used for fuel following a meal?
Only 2 hrs
43
What is used as fuel in starvation?
Glucose (hepatic gluconeogenesis) and FAs - 24 hrs | Ketone bodies - 48 hrs
44
What does the brain use as fuel in starvation? Muscles?
Brain - glucose then ketone bodies | Muscles - FAs
45
Intellectual disability + fair skin + eczema + seizures + musty body odor
Phenylketonuria - Phe hydroxylase or tetrahydobriopterin deficiency
46
Dark brown sclera + joint pain + urine turns black when exposed to air
Alkaptonuria = Homogentisate oxidase deficiency, homogentisic acid accumulation (toxic to cartilage)
47
Tall/kyphosis + intellectual disability + osteoporosis + downward lens subluxation + thrombosis
Homocysteinuria | Homocysteine accumulation damages endothelial cells, predisposing to thrombosis
48
What are 2 causes for homocysteinuria?
Cystathionine synthase dysfunction - deficiency or low affinity for vitB6 Homocysteine methyltransferase deficiency
49
Megaloblastic anemia + neurologic dysfunction (spinal cord demyelination) + normal methylmalonyl CoA
Homocysteinuria - homocysteine methyltransferase deficiency
50
Hexagonal cystine kidney stones
Cystinuria
51
What causes Cysteinuria? | How is it treated?
Defective transporter for Cys, Ornithine, Lys, and Arg (COLA) in renal proximal tubule and intestines Acetazolamide - alkalinizes the urine = basic AAs lose their protons and become charged = increased solubility in the filtrate
52
Neutral aminoaciduria + pellagra
Hartnup disease
53
What is the most immediate source of nitrogen for the urea cycle?
Aspartate
54
What infection may require vitamin A supplementation?
Measles - prevents exfoliative rash
55
Hemolytic anemia + ataxia/peripheral neuropathy + proximal muscle weakness with a poor diet
Vitamin E deficiency
56
What 2 vitamins must be given to exclusively breast-fed babies?
Vitamin C and D
57
Scaly skin + hepatomegaly + joint pain + headaches
Vitamin A toxicity (causes pseudotumor cerebri = headaches)
58
What non-collagen enzyme requires vitamin C?
Dopamine B-hydroxylase (DA to NE)
59
What vitamin facilitates Fe absorption?
Vitamin C (keeps Fe in the reduced 2+ state)
60
Confusion + opthalmoplegia + ataxia + memory loss
Wernicke-korsakoff syndrome (thiamine deficiency)
61
What 2 other conditions are caused by thiamine deficiency?
Wet Beriberi - high output heart failure | Dry Beriberi - polyneuropathy
62
Angular chelitis + gossitis
``` Vit B2 (flavin) or B6 (PLP) deficiency vitB6 def will also have convulsions (required to make GABA) ```
63
What are 3 causes of pellagra (vitB3 niacin deficiency)?
Hartnup disease, carcinoid syndrome, and isoniazid
64
Indication for niacin therapy
Low HDL
65
What vitamin deficiency can lead to adrenal insufficiency?
Vitamin B6 (pantothenate, CoA - acetylCoA used to make cholesterol)
66
Which vitamin is a cofactor for the aminotransferases?
Vitamin B6 (pyridoxine, PLP)
67
What two vitamins are depleted by isoniazid?
Vitamin B3 (niacin) and B6 (PLP)
68
What 4 medications can cause folate deficiency?
Phenytoin, sulfonamides, MTX/TMP
69
What type of reaction converts methylmalonyl-CoA to saucily-CoA requiring vitaminB12?
Isomerization reaction (methylmalonyl-CoA mutase)
70
GI bleeding with late metabolic acidosis and GI obstruction (weeks later)
Fe poisoning (ROS generation causes the GI damage and scarring causes obstruction)
71
What enzymes require Zn?
Carbonic anhydrase and LDH
72
What type of patients should receive Zn supplementation?
Delayed wound healing
73
Impaire night vision + infertility + delayed wound healing + anosmia + acrodermatitis enteropathica
Zn deficiency
74
Wrist/foot drop + colicky abdominal pain + bright horizontal lines near long-bone metaphyses
``` Lead poisoning (lead lines = deposition of lead in growing bone) Also causes anemia and basophilic stippling ```
75
Treatment for lead poisoning
Succimer or EDTA | Severe = succimer + dimercaperol
76
What are 2 causes of acrodynia (peeling skin off the finger tips)?
Kawasaki disease and Hg poisoning
77
CNS changes + enlarged kidneys + history of eating large fish like swordfish or shark
Hg poisoning
78
What 4 conditions are associated with Down syndrome?
Duodenal atresia, endocardial cushion defects, ALL ("we ALL fall DOWN"), and alzheimer's disease
79
What hematologic pathology is seen in newborns with Down syndrome?
Polycythemia
80
What are the 2 most common genetic causes for intellectual disability? What is the most common non-genetic cause?
Down syndrome then Fragile X syndrome | Fetal alcohol syndrome
81
What does the Quad screen look like in Down syndrome? | AFP, B-hCG, estriol, and inhibin A
AFP low, B-hCG high, estriol low, and inhibit A high | put in alphabetical order then start with down and alternate
82
What 3 congenital conditions will show nuchal translucency on 1st trimester ultrasound?
Down syndrome (trisomy 21), Patau syndrome (trisomy 13) and Turner syndrome
83
Micrognathia + clenched hands | Quad screen? (AFP, B-hCG, estriol, and inhibin A)
Edwards syndrome - trisomy 18 (Election age is 18 - Edwards) | AFP low, B-hCG low, estriol low, and inhibin A normal
84
Midline fascial defects/micropthalmia + polydactyly | What is used for prenatal detection?
Patau syndrome - trisomy 13 (Puberty at age 13 = Patau) | Decreased PAPP-A
85
What does FSH and LH look like in Klinefelters?
Abnormal seminiferous tubules = decreased Sertoli cell inhibin production = low FSH Abnormal Leydig cells = decreased testosterone = low FSH
86
Tall + developmental delay + testicular atrophy
Klinefelter syndrome (47XXY)
87
High pitched cry/mewing in newborn
Cri-Du-Chat = "cry of the cat" (chr5 short arm deletion)
88
Elfin facies + extreme friendliness + hyperCa + intellectual disabiltiy
Williams Syndrome - increased sensitivity to vitD = hyperCa | "WILL ferrel in ELF movie"
89
Advanced paternal age is associated with what condition of the child? What is the inheritance pattern?
Achondroplasia | Autosomal dominant FGFR3 mutation
90
Telangiectasia/AVMs throughout the body
Osler-Weber-Rendu (hereditary hemorrhagic telangiectasia)
91
What anemia is autosomal dominant?
Hereditary spherocytosis
92
What condition that predisposes to particular cancers is inherited in autosomal dominant pattern?
MEN
93
Intellectual disability + macroorchidism + mitral valve prolapse
Fragile X syndrome
94
What is the genetic cause of fragile X?
Trinucleotide repeat CGG | "Chromosome Girly-Girl = chr X"
95
Ataxia + hammer toes/pes cavus + hypertrophic cardiomyopathy + DM
Friedreich ataxia
96
What is the genetic cause of Friedreich ataxia?
Trinucleotide repeat GAA | "Gait Astoundingly Ataxic"
97
What antibiotic is used in CF that is not typically used in kids?
Fluoroquinolones
98
What condition is associated with gargoylism?
Hurler syndrome
99
What disorders are X-linked recessive? | "Oblivious Female Will Give Her Boys Her x-Linked Disorders"
Ocular albinism, Fabry disease, Wiscott-aldrich, G6PD deficiency, Hunter syndrome, Bruton agammaglobulinemia, Hemophilia A and B, Lesch-nyhan syndrome, and DMD

USMLE (12 decks)

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