Usmle Step 1 Review - Biochemistry

Front 1

achondroplasia (gene)

Back 1

FGFR3

Front 2

ADPKD (chr)

Back 2

chr 16

Front 3

familial hypercholesterolemia (type IIa) (gene)

Back 3

LDLR

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Huntington's disease (chr)

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chr 4

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NF1 (chr)

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chr 17

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NF2 (chr)

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chr 22

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VHL (gene, function, chr)

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VHL, tumor suppressor gene, chr 3

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CF (chr)

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chr 7

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Huntington's disease (XXX)n

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(CAG)n

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Myotonic dystrophy (XXX)n

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(CTG)n

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Friedreich's ataxia (XXX)n

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(GAA)n

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Fragile X syndrome (XXX)n

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(CGG)n

Front 13

Williams syndrome (del __)

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del 7q

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involved in decarboxylation reactions including pyruvate dehydrogenase, a-ketoglutarate dehydrogenase, transketolase, branched-chain amino acid dehydrogenase

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B1 - thiamine - TPP

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deficiency causes polyneuritis and muscle wasting and/or high-output heart failure

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beriberi, from B1 - thiamine - TPP deficiency

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syndrome with ophthalmoplegia, ataxia, and confusion

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Wernicke's encephalopathy, from B1 - thiamine - TPP deficiency

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syndrome with confabulation, permanent memory loss, and hallucinations

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Korsakoff's psychosis from B1 - thiamine - TPP deficiency

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cofactor in redox reactions (FAD)

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B2 - riboflavin - FAD/FMN

Front 19

deficiency causes cheliosis, corneal revascularization, as well as glossitis and dermatitis

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B2 - riboflavin - FAD/FMN

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cofactor in redox reactions (NAD)

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B3 - niacin - NAD+

Front 21

vitamin whose synthesis requires vitamin B6

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B3 - niacin - NAD+

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deficiency causes diarrhea, dermatitis, dementia

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B3 - niacin - NAD+

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vitamin involved in acyl transfers performed by fatty acid synthase

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B5 - pantothenate - CoA

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deficiency causes dermatitis, enteritis, alopecia, and adrenal insufficiency

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B5 - pantothenate - CoA

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vitamin required for the synthesis of cystathionine, heme, niacin, and GABA

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B6 - pyridoxine - PLP

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vitamin involved in transamination, decarboxylation, and glycogen phosphorylase

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B6 - pyridoxine - PLP

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deficiency causes seizures, peripheral neuropathy, and sideroblastic anemia

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B6 - pyridoxine - PLP

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deficiency can be precipitated by isoniazid or OCPs

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B6 - pyridoxine - PLP

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vitamin involved in 1-carbon transfer (methylation) reactions

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B9 - folic acid - THF

Front 30

vitamin important for synthesis of dTMP

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B9 - folic acid - THF

Front 31

deficiency causes megaloblatic anemia without neurological symptoms in adults, but causes neural tube defects in fetuses

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B9 - folic acid - THF

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vitamin is a cofactor for homocysteine methyltransferase and methylmalonyl-CoA mutase

Back 32

B12 - cobalamin

Front 33

deficiency causes megaloblastic anemia, hypersegmented neutrophils, parasthesias, subacute combined degeneration (irreversible)

Back 33

B12 - cobalamin

Front 34

cofactor for carboxylation enzymes that is synthesized in the gut

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B7 - biotin

Front 35

deficiency causes dermatitis, alopecia and enteritis; can be precipitated by avidin in raw egg whites

Back 35

B7 - biotin

Front 36

an antioxidant that facilitates Fe absorption by keeping it reduced; also necessary for dopamine B-hydroxylase

Back 36

vitamin C - ascorbic acid

Front 37

deficiency leads to swollen gums, bruising, bleeding, anemia, poor healing, and immunodeficiency

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vitamin C - ascorbic acid - syndrome is scurvy

Front 38

deficiency causes night blindness, dry skin

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vitamin A - retinol

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component of rhodopsin and an anti-oxidant

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vitamin A - retinol

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D2 is called...

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ergocalciferol

Front 41

D3 is called...

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cholecalciferol (from milk, sun)

Front 42

storage form of vitamin D

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25(OH)-D3

Front 43

active form of vitamin D

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1,25(OH)-D3 (calcitriol)

Front 44

increases intestinal absorption of Ca and phosphate, and increases bone resorption

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vitamin D

Front 45

excess causes hypercalcemia, hypercalcuria, anorexia and stupor

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vitamin D toxicity

Front 46

an important antioxidant; deficiency can cause hemolytic anemia as well as posterior column and spinocerebellar tract demyelination leading to sensory deficits, stupor

Back 46

vitamin E

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catalyzes gamma-carboxylation of glutamic acid residues

Back 47

vitamin K

Front 48

deficiency can cause abnormal collagen cross-linking as well as muscle weakness and neurological deficits

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copper

Front 49

deficiency can cause congestive cardiomyopathy (Keshan disease)

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selenium

Front 50

deficiency can cause growth retardation and poor wound healing

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zinc

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RDS of glycolysis

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PFK1

Front 52

RDS of gluconeogenesis

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F-1,6-bisphosphatase

Front 53

RDS of TCA cycle

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isocitrate dehydrogenase

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RDS of glycogen synthesis

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glycogen synthase

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RDS of glycogenolysis

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glycogen phosphorylase

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RDS of HMP shunt

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G6PD

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RDS of de novo pyrimidine synthesis

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carbamoyl phosphate synthase II

Front 58

RDS of de novo purine synthesis

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glutamine-PRPP aminotransferase

Front 59

RDS of urea cycle

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carbamoyl phosphate synthase I

Front 60

RDS of fatty acid synthesis

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acetyl-CoA carboxylase

Front 61

RDS of fatty acid oxidation

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carnitine acyltransferase I

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RDS of ketogenesis

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HMG-CoA synthase

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RDS of cholesterol synthesis

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HMG-CoA reductase

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site of fatty acid oxidation

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mitochondria

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site of acetyl-CoA production

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mitochondria

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site of TCA cycle

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mitochondria

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site of electron transport chain

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mitochondria

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site of glycolysis

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cytoplasm

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site of fatty acid synthesis

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cytoplasm

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site of HMP shunt

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cytoplasm

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site of protein synthesis

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rough ER and free ribosomes in the cytoplasm

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site of steroid synthesis

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smooth ER

Front 73

site of protein sorting and modificaction

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Golgi apparatus

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site of heme synthesis

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both mitochondria and cytoplasm

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site of urea cycle

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both mitochondria and cytoplasm

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site of gluconeogenesis

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both mitochondria and cytoplasm

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in the heart and liver, 1 glucose makes ___ ATP due to the malate-aspartate shuttle

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32

Front 78

in the muscle, 1 glucose makes ___ ATP due to the glycerol-3-phosphate shuttle

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30

Front 79

aromatic essential amino acids

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phenylalanine, tryptophan

Front 80

branched chain essential amino acids

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valine, isoleucine, leucine

Front 81

polar but uncharged essential amino acids

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methionine, threonine

Front 82

basic essential amino acids

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histidine, lysine

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acidic amino acids (not essential)

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aspartate, glutamate

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basic amino acids (all)

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histidine, arginine, lysine

Front 85

defect in glucose-6-phosphatase

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Von Gierke's disease (GSD type I)

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defect in lysosomal alpha-1,4-glucosidase (aka acid maltase)

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Pompe's disease (GSD type II)

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defect in alpha-1,6-glucosidase (debranching enzyme)

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Cori's disease (GSD type III)

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defect in skeletal muscle glycogen phosphorylase

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McArdle's disease (GSD type V)

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build-up of ceramide trihexoside

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Fabry's disease (x-linked)

Front 90

deficiency of alpha-galactosidase

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Fabry's disease (X-linked)

Front 91

deficiency of glucocerebrosidase

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Gaucher's disease

Front 92

build-up of glucocerebroside

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Gaucher's disease

Front 93

build-up of sphingomyelin

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Niemann-Pick disease

Front 94

deficiency of sphingomyelinase

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Niemann-Pick disease

Front 95

build-up of GM2 ganglioside

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Tay-Sachs disease

Front 96

deficiency of hexosaminidase A

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Tay-Sachs disease

Front 97

defect of galactocerebrosidase

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Krabbe's disease

Front 98

build-up of galactocerebroside

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Krabbe's disease

Front 99

defect of arylsulfatase A

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metachromatic leukodystrophy

Front 100

buildup of cerebroside sulfate

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metachromatic leukodystrophy

Front 101

deficiency of alpha-L-iduronidase

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Hurler's syndrome

Front 102

deficiency of iduronate sulfatase

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Hunter's syndrome (X-linked)

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build-up of heparan sulfate and dermatan sulfate

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Hunter's and Hurler's syndromes

Front 104

essential amino acids (list them)

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phenylalanine, tryptophan (aromatic); leucine, isoleucine, valine (branched); methionine, threonine (polar); histidine, lysine (basic)

Front 105

defect in ability to transfer enzymes from lysosomes to phagocytic vesicles --> infections, anemia, thrombocytopenia

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Chediak-Higashi syndrome

Front 106

for a non-competitive inhibitor, is Km or Vmax the same?

Back 106

Km

Front 107

for a competitive inhibitor, is Km or Vmax the same?

Back 107

Vmax

Front 108

antidote for AChE inhibitors

Back 108

pralidoxime chloride

Front 109

gamma-glytamyl transferase (GGT) is elevated in

Back 109

biliary obstructions, pancreatic cancer, and alcohol-induced liver disease

Front 110

autosomal dominant mutations in glucokinase result in

Back 110

MODY

Front 111

Which has a high Km (low affinity), glucokinase or hexokinase?

Back 111

Glucokinase, because this is how the liver senses blood glucose levels. Hexokinase has a low Km and is constitutively active

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F-2,6-BP ____ PFK-1

Back 112

stimulates

Front 113

AMP ___ PFK-1

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stimulates

Front 114

ATP ____ PFK1

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inhibits

Front 115

citrate ___ PFK1

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inhibits

Front 116

FADH2 is worth ___ molecules of ATP

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1.5

Front 117

NADH is worth ___ molecules of ATP

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2.5

Front 118

1 acetyl-CoA is worth ___ molecules of ATP

Back 118

10

Front 119

pyruvate carboxylase requires the vitamin...

Back 119

B7, biotin

Front 120

alpha-ketoglutarate dehydrogenase and pyruvate dehydrogenase require the vitamin...

Back 120

B1, thiamine, TPP

Front 121

Leber's hereditary optic neuropathy results from...

Back 121

defect in mtDNA (cytochrome reductase) --> loss of central vision in males in 3rd decade

Front 122

number of ATP required to synthesize 1 molecule of glucose via gluconeogenesis

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6

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causes accumulation of oxalate in type I primary oxaluria

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missing the transaminase that converts glyoxalate to glycine

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causes histidinemia

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missing histidase

Front 125

causes excessive production of methyl citrate, a TCA poison

Back 125

methylmalonyl CoA mutase deficiency

Front 126

causes accumulation of homocystine and methionine (homocystinuria)

Back 126

defect in cystathionine B synthase

Front 127

causes accumulation of branched-chain amino acids (valine, isoleucine, leucine)

Back 127

maple syrup urine disease, deficiency of alpha-ketoacid dehydrogenase

Front 128

causes build-up of homogentisic acid (alkaptonuria)

Back 128

deficiency of homogentisate oxidase

Front 129

causes build-up of isovaleryl CoA, a leucine degradation product (isovaleric acidemia)

Back 129

deficiency of isovaleryl CoA dehydrogenase

Front 130

MR, spasticity, seizures, HSM, cherry red macula, ataxia, death by 2-3

Back 130

Niemann-Pick disease

Front 131

neurodegeneration, cherry red macula, no HSM, death by age 4

Back 131

Tay-Sachs disease

Front 132

acroparesthesias (extremity pain), angiokeratomas, hypohidrosis, ischemic infarction of kidneys, heart, and brain

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Fabry disease

Front 133

demyelination leads to spasticity, decerebrate posturing, blindness, deafness, and death

Back 133

Krabbe disease

Front 134

HSM, thrombocytopenia, Erlenmeyer flask deformity of distal femur

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Gaucher disease

Front 135

demyelination leads to neurological decline, ataxia, hyporeflexia, and seizures

Back 135

metachromatic leukodystrophy

Front 136

periodic attacks of renal colic, neuropathy, psychosis, and tachycardia; precipitated by drugs like steroids, barbiturates, and alcohol

Back 136

acute intermittent porphyria (autosomal dominant)

Front 137

defect in uroporphyrinogen decarboxylase

Back 137

porphyria cutanea tarda, leads to photosensitivity with bullae

Front 138

defective enzyme in acute intermittent porphyria

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hydroxymethylbilane synthase (aka porphobilinogen deaminase)

Front 139

alcoholics have high or low NADH/NAD+ ratio

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HIGH (too much NADH)

Front 140

hormone that acts through a tyrosine kinase that stimulates IRS-1

Back 140

insulin

Front 141

hormones that act through a GPCR --> adenylate cyclase --> ATP to cAMP --> PKA

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glucagon, EPI

Front 142

hormone that signals increased blood volume; signals through a GPCR --> PKG

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atrial natriuretic peptide

Front 143

hormones that signal through a GPCR --> PKC

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TRH, oxytocin

Front 144

thyroid hormones, vitamin D, and retinoic acid act in the...

Back 144

nucleus!

Front 145

ataxia-telangiectasia is a DNA repair defect affecting...

Back 145

ability to repair damage from ionizing radiation; leads to T-cell leukemias and lymphomas

Front 146

Bloom syndrome is a DNA repair defect affecting...

Back 146

ability to repair DNA damage from UV exposure; leads to skin cancer

Front 147

Fanconi anemia is a DNA repair defect affecting...

Back 147

DNA cross-linking repair with sensitivity to nitrogen mustards; leads to leukemia

Front 148

Li-Fraumeni syndrome is a defect in ___ affecting DNA repair...

Back 148

p53; permits cell to pass cell cycle checkpoints despite messed up DNA; leukemia, sarcoma, breast CA, CNS tumors

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HNPCC is a DNA repair defect affecting...

Back 149

mismatch repair; leads to colon, ovarian, and endometrial cancer

Front 150

xeroderma pigmentosum is a DNA repair defect affecting

Back 150

ability to repair thymidine dimers caused by UV; leads to skin and ocular cancers