Biochemistry

Question 1

Von Gierke’s disease

Answer 1

Type 1 Glycogen storage disease

Deficient in glucose 6 phosphatase -> severe fasting hypoglycemia, Increased glycogen in liver (hepatomegaly), increase blood lactate

Question 2

Pompe’s Disease

Answer 2

Type 2 Glycogen storage disease

Deficient lysosomal a-1,4 glucosidase (acid maltase)

Cardiomegaly and systemic findings -> early death

“pompe’s trash the pump (heart, liver, muscle)”

Question 3

Cori’s Disease

Answer 3

Type 3 Glycogen storage disease

Deficient debranching enzyme (a-1,6 glucosidase)

Milder form of type 1 with normal blood lactate (gluconeogensis intact)

Question 4

McArdle’s disease

Answer 4

Type 5 Glycogen storage disease

Deficient in muscle glycogen phosphorylase -> Increase glycogen in muscle (cannot break it down) -> painful muscle cramps, myoglobinuria with strenuous exercise

Question 5

Rate limiting enzyme: glycolysis

Answer 5

PFK-1

Question 6

Rate limiting enzyme: Gluconeogenesis

Answer 6

Fructose 1,6 bisphosphatase

Question 7

Rate limiting enzyme: TCA

Answer 7

Isocitrate dehydrogenase

Question 8

Rate limiting enzyme: Glycogen synthesis

Answer 8

Glycogen synthetase

Question 9

Rate limiting enzyme: glycogenolysis

Answer 9

Glycogen phosphorylase

Question 10

Rate limiting enzyme: HMP shunt (pentose phosphate pathway)

Answer 10

Glucose-6-phosphate dehydrogenase

Question 11

Rate limiting enzyme: De novo pyrimidine synthesis

Answer 11

Carbamoyl phsphate synthetase II

Question 12

Rate limiting enzyme: De novo purine synthesis

Answer 12

Gluatmine-PRPP synthetase

Question 13

Rate limiting enzyme: Urea cycle

Answer 13

CPS-1

Question 14

Rate limiting enzyme: Fatty Acid synthesis

Answer 14

Acetyl-CoA carboxylase

Question 15

Rate limiting enzyme: Fatty Acid Oxidation

Answer 15

Carnitine acyl-transferase 1

Question 16

Rate limiting enzyme: ketogenesis

Answer 16

HMG-CoA synthase

Question 17

Rate limiting enzyme: Cholesterol Synthesis

Answer 17

HMG-CoA reductase

Question 18

Quad screen of Trisomy 21

Answer 18

Decrease AFP

Increase B-hCG

Decrease Estriol

Increase Inhibin A

US - Increase nuchal translucency

Question 19

Quad screen of Trisomy 13

Answer 19

Decrease AFP

Decreaese B-hCG

Decrease estriol

Normal Inhibin A

Question 20

Quad screen of Trisomy 18

Answer 20

Decrease B-hCG

Decrease PAPP-A

Increase nuchal translucency

Question 21

Characteristics of Downs (Trisomy 21)

Answer 21

Mental retardation, flat facies, prominent epicanthal folds, simian crease, gap between toes, duodenal atresia, congenital heart disease (ASD)

Question 22

Characteristics of Edwards (Trisomy 18)

Answer 22

Mental retardation, Rocker bottom feet, micrognathia, low-set Ears, clenched hands, prominent occiput, congenital heart disease

Question 23

Characteristics of Patau (Trisomy 13)

Answer 23

Mental retardation, rocker bottom feet, microphthalmia, microcephaly, cleft liP/_P_alate, holoProsencephaly, Polydactyly, congenital heart disease

Question 24

Fabry’s disease

Defective enzyme

findings

Accumulated substance

Answer 24

Defective enzyme: a-galatosidase A (X-linked recessive)

Findings: Peripheral neuropathy of hands, feet, angiokeratoma, cardiovascular/renal disease

Accumulated: Ceramide trihexoside

Question 25

**Gaucher's disease** Defective enzyme Findings Accumulaiton

Answer 25

Defective enzyme: B-glucocerebrosidase (Autosomal recessive) ## Footnote Findings: RBC dying off -\> accmulate in liver, spleen, bone. Hepatosplenomegaly, **aseptic necrosis of femur**, **macorphage looks like crumped paper** Accumulaiton: Glucocerebroside

Question 26

**Niemann-Pick** Defective enzyme Findings Accumulaiton

Answer 26

Defective enzyme: sphingomyelinase Findings: Progressive neurodengeneration, hepatospelnomegaly, _cherry-red spot on macula_, foam cells Accumulaiton: sphingomyelin

Question 27

**Tay-Sachs Disease** Defective enzyme Findings Accumulaiton

Answer 27

Defective enzyme: He**X**ominadase A in Tay-Sa**X** ## Footnote Findings: Progressive neurodegneration, developmental delay, _cherry-red spot on macula_, lysosomes with onion skin, **no hepatosplenomegaly (vs. Niemann Pick)** Accumulaiton: GM2 ganglioside (build up in ganglion)

Question 28

**Krabbe's disease** Defective enzyme Findings Accumulaiton

Answer 28

Defective enzyme: Galactocerebrosidase ## Footnote Findings: Peripheral neuropathy, developmental delay, **optic atrophy, globoid cells** Accumulaiton: Galactocerebrosidase

Question 29

**Metachromatic leukodystrophy** Defective enzyme Findings Accumulaiton

Answer 29

Defective enzyme: Arysulfatase A ## Footnote Findings: Central and peripheral demyelination with ataxia, dementia Accumulaiton: Cerebroside sulfate

Question 30

Hurler's disease Defective enzyme Findings Accumulaiton

Answer 30

Defective enzyme: a-**L**-iduronidase in Hur**L**er ## Footnote Findings: Developmental delay, gargoylism, airway obstruction, _corneal clouding_ Accumulaiton: Heparan sulfate

Question 31

Hunter's disease Defective enzyme Findings Accumulaiton

Answer 31

Defective enzyme: Iduronate sulfatase (X-linked recessive) Findings: Mild hurler's, aggressive behavior, _no corenal clouding_ Accumulation: Heparan sulfatate

Question 32

Vimentin stains for?

Answer 32

Connective tissue (sarcoma, some carcinoma)

Question 33

Desmin stains for?

Answer 33

Muscles (rhabdomyosarcoma, leiomyomas)

Question 34

Cytokeratin stains for?

Answer 34

Epithelial cells (carcinomas)

Question 35

GFAP stains for?

Answer 35

Neuroglia

Question 36

Neurofilaments stains for?

Answer 36

Neurons (adrenal renal blastomas, primitive ectodermal tumor)