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Step Study Notes > Biochem > Flashcards

Biochem Flashcards

1
Q

Purines

A

A, G, 2 rings, easier to make

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2
Q

Pyrimidines

A

C, T, U, 1 ring, harder to make

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3
Q

Amino acids necessary for purine synthesis

A

GAG, Glitter and Glue (Glycine, Aspartate, Glutamine)

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4
Q

Drugs blocking purine synthesis

A

MMF, Ribavirin (IMP dehydrogenase)
HU (ribonucleotide reductase)
6-MP, azathioprine (de novo purine synthesis)

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5
Q

Drugs blocking pyrimidine synthesis

A

Leflunomide (dihydroorage dehydrogenase)
HU (ribonucleotide reductase)
5-FU (thymidylate synthase)
MTX, tMP, pyrimethamine (DHFR in human, bacteria, protozoa, respectively)

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6
Q

Transition

A

Purine to purine or pyrimidine t pyrimidine (moving down the street)

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7
Q

Transversion

A

Purine to pyrimidine or vice versa (crossing the street)

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8
Q

N-oligosaccharides

A

asparagine

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9
Q

O-oligosaccharides

A

Serine, threonine

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10
Q

M6P

A

Proteins going to the lysosome

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11
Q

Type 1 Cartilage

A

Bone
Skin
Tendon

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12
Q

Type 2 Cartilage

A

Hyaline cartilage
Vitreous Body
Nucleus pulposus

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13
Q

Type 3 Cartilage

A

Reticulin (skin blood vessels, uterus, fetal tissue, granulation tissue)

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14
Q

Type 4 Cartilage

A

Basement membrane, basal lamina, lens

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15
Q

Heterodisomy

A

2 copies of chromosome from one parent due to meiosis I error, none from other parent

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16
Q

Isodisomy

A

2 copies of chromosome fron one parent due to meiosis II or postzygotic duplication, none from other parent

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17
Q

ADPKD

A

AD, PKD1 and 2, cystic kidneys, sometimes liver and pancreas

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18
Q

Familial Adenomatous Polyposus

A

APC gene, adenomatous polyps, progress to cancer unless resect colon

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19
Q

Familial Hypercholesterolemia

A

AD, LDL-receptor gene, severe atherosclerosis, xanthomas

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20
Q

HHT

A

AD, disorder of blood vessels, telangiectasias, epistaxis, skin discoloration, AVM, GI bleeds, hematuria

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21
Q

Hereditary spherocytosis

A

AD, spectrin or ankyrin gene, spheroid erythrocytes resulting in hemolytic anemia, increased MCHC, RDW

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22
Q

Huntington

A

AD, trinucleotide repeat disease CAG in huntingtin gene, chorea, dementia, caudate atrophy, depression, increased DA, decreased GABA, ACh

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23
Q

Li Fraumeni Syndrome

A

AD, P53 Gene, multiple malignancies

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24
Q

Marfan syndrome

A

AD, fibrillin gene, CTD affecting skeleton, heart, eyes, tall, long extremities, pectus excavatum, hypermobile joints, arachnodactyly, cystic medial necrosis of aorta –> aortic incompetence and dissecting aneurysms, floppy mitral valve, subluxation of lenses

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25
Q

MEN

A

AD, MEN1: MEN1 gene, MEN2: RET gene, multiple endocrine neoplasias

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26
Q

NF

A

AD
NF1: NF1 gene, chr17, CALM, neurofibroma, optic glioma, pheochromocytoma, lisch nodule
NF2: NF2 gene, chr22, schwannomas, meningomas, ependymomas

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27
Q

TSC

A

TSC1 and 2 benign hamartomas

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28
Q

VHL

A

VHL gene, chr3, numerous tumors,

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29
Q

Serology findings for trisomy 21

A

First trimester:

  • serum PAPPa down
  • free beta-HCG up,
  • increased nuchal translucency

Second trimester:

  • alpha-fetoprotein and estriol down
  • free beta-HCG and inhibin A up
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30
Q

Serology findings for trisomy 18

A

First trimester:
- PAPPa and beta-HCG down
Second trimester:
- alpha-fetoprotein, beta-HCG, estriol and inhibin A down (or normal inhibin A)

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31
Q

Serology findings for trisomy 13

A

First trimester:

- free betaHCG and PAPPa down, increased nuchal translucency

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32
Q

Vitamin A deficiency

A 
night blindness
dry scaly skin
corneal degeneration
bitot spots on conjunctiva
immunosuppression
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33
Q

Vitamin A excess

A

Retinol

Acute:
N&V
vertigo
blurred vision
Chronic: 
alopecia
dry skin
hepatic toxicity and enlargement
arthralgias
psurdotumor cerebri
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34
Q

Vitamin B1 deficiency

A

Adult-acquired: Wernicke-Korsakoff
Thiamine

confusion and memory loss
opthalmoplegia
ataxia
nystagmus
confabulation and personality change

Childhood-acquired:
Dry beriberi: polyneuritis, muscle wasting
Wet beriberi: high-throughput cardiac failure (DCM), edema

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35
Q

Vitamin B2 deficiency

A

Riboflavin

cheilosis
corneal vacularization

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36
Q

Vitamin B3 deficiency

A

Niacin (derived from tryptophan)

Glossitis
Pellagra (diarrhea, dementia/hallucinations, dermatitis)

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37
Q

Vitamin B3 excess

A

Niacin (derived from tryptophan), lowers VLDL, raises HDL

Facial flushing (PG-mediated, avoid w/aspirin)
Hyperglycemia
Hyperuricemia

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38
Q

Vitamin B5 deficiency

A

Pantothenic acid

dermatitis
enteritis
alopecia
adrenal insufficiency

39
Q

Vitamin B6 deficiency

A

Pyridoxine

convulsions
hyperirritability
peripheral neuropathy (esp w/isoniazid and OCP tx)
sideroblastic anemia

40
Q

Vitamin A

A 
visual pigments
epithelial differentiation
block squamous metaplasia
tx measles, AML3
liver and leafy veggies
41
Q

Vitamin B1

A

alpha ketoglutarage dehydrogenase
transketolase (HMP shunt)
pyruvate dehydrogenase
branced chain ketoacid dehydrogenase

42
Q

Vitamin B2

A

component of flavins FAD and FMN, used in TCA cycle

43
Q

Vitamin B3

A

component of NAD, NADP used in redox reactions

require b2 and b6 for sx

44
Q

Vitamin B5

A

essential component of coenzyme A (CoA) and FA synthase

45
Q

Vitamine B6

A 
converted to pyridoxal phosphate, used for:
transamination
decarboxylation
glycogen phosphorylase
Sx of:
heme
niacin
histamine
NT's (Serotonin, Epi, NE, Da, GABA)
46
Q

Vitamin B7

A

cofactor for carboxylation enzymes (which add 1 carbon at a time)

47
Q

Vitamin B7 deficiency

A

Biotin (caused by abx use or egg white ingestion)

Dermatitis
Alopecia
enteritis

48
Q

Vitamin B6

A

Converted to tetrahydrofolic acid
coenzyme for 1-carbon transfer/methylation
synthesis of nitrogenous bases in DNA and RNA
leafy green vegetables
absorbed in jejunum
reservoir in liver

49
Q

Vitamin B6 deficiency

A

Folate (deficiency in alcohol, pregnancy, phenytoin, sulfonamide, mtx use)

Macrocytic, megaloblastic anemia
hypersegmented PMN’s
glossitis
neural tube defects in pregnancy

Labs:

incr. homocysteine
nl. MMA

50
Q

Vitamin B12

A

cofactor for

  • homocysteine methyltransferase (make methionine from homocysteine)
  • methylmalonyl-CoA mutase (part of heme production pathway from FA, branched chain aa’s)

found in animal products
synthesized only by microorganisms
large reservoir pool in liver

51
Q

Vitamin B12 Deficiency

A

Cobalamin (Deficiency caused by insufficient intake, malabsorption, lack of IF, gastric bypass, absence of terminal ileum, tapeworm, anti-IF antibody)

Macrocytic, megaloblastic anemia
hypersegmented PMN's
paresthesias 
subacute combined degeneration (demyelination of dorsal column, lateral corticospinal tracts, and spinocerebellar tracts resulting in:
- large fiber sensory polyneuropathy
- nerupsych. symptms
- optic neuropathy)

Labs:
incr. homocysteine AND mma

52
Q

Vitamin C

A

antioxidant
facilitates iron absorption by reducing to Fe2+ state
necessary for hydroxylation of proline and lysine in collagen synthesis
necessary for conversion of DA to NE (dopamine beta hydroxylase)

found in fruits and veggies
tx for methemoglobinemia by reducing iron

53
Q

Vitamin C deficiency

A

Ascorbic Acid

Scurvy (collagen synth. defect)

  • swollen gums
  • buising
  • petechiae
  • hemarthrosis
  • anemia
  • poor wound healing
  • perifollicular and subperiosteal hemorrhage
  • corkscrew hair
  • weakened immune system
54
Q

Vitamin C excess

A 
N&V
diarrhea
fatigue
calcium oxalate nephrolithiasis
increased risk of iron tox in predisposed people
55
Q

Vitamin D

A

Ergocalciferol from plants, cholecalciferol from milk, made in skin

converted to calcitriol (1,25-OH-D)

increases intestinal absorption of phosphate and calcium
increases bone mineralization

Breasfeeding: give supplemental oral vitamin D to baby

56
Q

Vitamin D deficiency

A
  • Deficiency in breastfed children, low sun exposure, pigmented skin, prematurity

Rickets in children (bone pain with deformity)
Osteomalacia in adults (bone pain with muscle weakness)
Hypocalcemic tetany

57
Q

Vitamin D excess

A

Hypercalcemia, hypercalciuria
Loss of appetite
Stupor

Sometimes seen in granulomatous disease due to activation by epithelioid macrophages

58
Q

Vitamin E

A

Antioxidant that protects RBCs and membranes from free radical damage
Enhances anticoagulation effects of warfarin

59
Q

Vitamin E deficiency

A

Tocopherol/Tocotrienol

Hemolytic anemia
Acanthocytosis
Muscle weakness
Posterior column and spinocerebellar tract demyelination (similar to B12 deficiency w/o megaloblastic anemia and hypersegmented PMNs, or increased MMA)

60
Q

Vitamin K

A 
Cofactor for gamma-carboxylation of glutamic acid on proteins needed for clotting (Factors 2, 7, 9, 10, protein C and protein S)
Synthesized by intestinal flora
Note: 
- neonates have sterile intestines
- not in breast ilk
- abx tx will destroy flora
61
Q

Vitamin K deficiency

A

Neonatal hemorrhage with increased PT and PTT (nl bleeding time)

62
Q

Zinc

A

essential for enzyme activity, transcription factors

63
Q

Zinc deficiency

A 
Delayed wound healing
Hypogonadism
Decreased adult hair
Dysgeusia
Anosmia
Acrodermatits enteropathic

Alcoholic cirrhosis predisposition

64
Q

Kwarsiorkor

A

Protein malnutrition

  • skin lesions
  • edema
  • liver malfunction (fatty change)
  • anemia
65
Q

Marasmus

A

Total calorie malnutrition:

  • tissue and muscle wasting
  • loss of subQ fat
  • variable edema
66
Q

Arsenic

A
  • causes glycolysis to produce zero net ATP
  • inhibits lipoic acid (cofactor for pyruvate dehydrogenase complex)
  • Produces: vomiting, rice-water stools, gralic breath
67
Q

Pyruvate dehydrogenase complex deficiency

A
  • pyruvate buildup because cannot be used in TCA cycle
  • pyruvate shunted to lactate and alanine
  • X-linked (or due to nutritional deficiency of cofactors)
  • see neurologic defects, lactic acidosis, increased serum alanine
  • if X-linked: increase intake of ketogenic nutrients leucine and lysine (the only purely ketogenic aa’s)
68
Q

Rate-limiting step of glyolysis

A

phosphofructokinase (fructose 6-phosphate to fructose 1,6-bisphosphate)

69
Q

Rate-limiting step of gluconeogenesis

A

fructose 1,6 bisphosphatase (f 1,6 BP to F6P)

70
Q

Rate-limiting step of TCA cycle

A

isocitrate dehydrogenase (isocitrate to alpha ketoglutarate)

71
Q

Rate-limiting step of glycogenesis

A

glycogen synthase

72
Q

Ketogenic aa’s

A

Leucine and lysine

73
Q

Essential aa’s

A

LiL HuMVee PITT:

  • LiL = Leucine, lysine, ketogenic
  • HMV = His, Met, Val, glucogenic
  • PIT = Phe, Ile, Thr, Trp, gluco/ketogenic
74
Q

Pyruvate dehydrogenase deficinecy

A
  • can’t use pyruvate in TCA
  • X-linked
  • lactic acidosis, neruo. defects, high serum alanine
  • consume ketogenic compounds (fat, leucine, lysine)
75
Q

N-acetylglutamate synthase deficiency

A
  • cannot use carbamoyl phosphate syntase 1 deficiency to allow NH3 to enter urea cycle.
  • accumulate ammonia
  • neonates: poorly regulated body temp, respiration, poor feeding, developmental delay and ID
76
Q

Ornithine transcarbamylase deficiency

A
  • most common
  • X-linked recessive
  • interferes with ammonia elimination
  • increased orotic acid due to shunting of excess carbamoyl phosphate
  • decreased BUN
  • symptoms of hyperammonemia
  • NO megaloblastic anemia
77
Q

PKU

A
  • deficiency of Phenylalanine Hydroxylase OR Tetrahydrobipterin Cofactor
  • Autosomal recessive
  • ID, growth retard, seizure, fair skin, musty body odor
  • Maternal: neonate with ID, microcephaly, growth retard. heart defects
78
Q

Maple Syrup Urine

A
  • deficiency of Alpha-ketoacid dehydrogenase
  • degradation of branched amino acids is blocked (leucine, isoleucine, valine)
  • CNS defects, ID, death
  • urine smelling like burnt sugar, increased alpha ketoacids in blood, esp from leucine
79
Q

Alkaptonuria

A
  • deficiency of homogentisate oxidase
  • cannot degrade tyrosine to fumarate
  • accumulate pigment-formine homogentisic acid in tissues
  • dark connective tissue, brown pigmented sclerae, urine turns black when exposed to air,
  • arthralgias possible
80
Q

Homocystinuria

A

3 types, all autosomal recessive

  • deficiency or decreased B6 affinity of cystathione synthase (makes cysteine)
  • deficiency of homocysteine methyltransferase (makes methionine)
  • all have excess urinary homocysteine, ID, osteoporosis, marfanoid habitus, kyphosis, lens subluxation (down and in), thrombosis, atherosclerosis
81
Q

Cystinuria

A
  • amino acid transporter (PT and intestine)
  • inability to reabsorb COAL (cysteine, ornithine, arginine, lysine)
  • hexagonal cystine stones
  • alkalinize urine, hydrate, chelation,
  • dx w/CN nitroprusside urinary test
82
Q

Von Gierke Disease

A
  • Defect in G6 phosphatase
  • cannot release glucose from liver cells
  • hepatomegaly, high glycogen in liver, lactic acidosis, increased uric acid, increased tg’s
83
Q

Pompe disease

A
  • defect in alpha 1,4 glucosidase (alternative enzyme for degrading glycogen in lysosome)
  • cardiomegaly, hypertrophic cardiomyopathy, floppy baby, early death
84
Q

Cori disease

A
  • debranching enzyme (alpha 1,6 glucosidase) deficiency

- mild disease with normal blood lactate

85
Q

McArdle Disease

A
  • deficiency of muscle glycogen phosphorylase
  • muscles cannot release glucose from glycogen
  • increased muscle glycogen, muscle cramps, myoglobinuria w/exercise, arrhythmia from electrolyte abnormalities, normal blood glucose
  • tx with B6 (cofactor)
86
Q

Fabry

A

Deficiency: Alpha galactosidase A (XR)
Buildup: Ceramide trihexidose

Sx: acroparesthesia, hypohidrosis, angiokeratoma, CV/Renal/GI complications, corneal opacity

87
Q

Gaucher

A

Deficiency: Glucocerebrosidase (AR)
Buildup: Glucocerebroside

Sx: HSM, erlenmyer flask bones, pancytopenia, osteoporosis, aseptic necrosis of femur, gaucher cells

88
Q

Niemann-Pick

A

Deficiency: Sphingomyelinase (AR)
Buildup: sphingomyelin

Sx: progressive neurodegeneration, HSM, foam cells, cherry red spot, ILD/recurrent lung infection

89
Q

Tay-Sachs

A

Deficiency: Hexosaminidase A (AR)
Buildup: GM2 ganglioside

Sx: progressive neurodegeneration, foam cells, cherrry red spot, lysosomes with onion skin

90
Q

Krabbe

A

Deficiency: Galactocerebrosidase (AR)
Buildup: galactocerebroside, psychosine

Sx: peripheral neuropathy, developmental delay, optic atrophy, globoid cells

91
Q

Metachromatic Leukodystrophy

A

Deficiency: Arylsulfatase A (AR)
Buildup: cerebroside sulfate

Sx: central and peripheral demyelination with ataxia, dementia

92
Q

Hurler

A

Deficiency: Alpha-L-Iduronidase (AR)
Buildup: heparan sulfate, dermatan sulfate

Sx: developmental delay, gargoylism, airway obstruction, corneal clouding, HSM

93
Q

Hunter

A

Deficiency: Iduronate sulfatase (XR)
Buildup: heparan sulfate, dermatan sulfate

Sx: mild hurler + aggressive behavior, no corneal clouding

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