Usmle Step 1 Biochemistry: Paul

Front 1

What is the result of Vitamin A deficiency?

Back 1

night blindness

Front 2

What are the different types of GLUT transporters and where are they found?

Back 2

GLUT1: brain, RBCs
GLUT2 (bidirectional): B islet cells, liver, kidney
GLUT4: muscle, adipose

Front 3

Which tissues do not require insulin for glucose uptake?

Back 3

brain, RBCs, intestine, cornea, kidney, liver

Front 4

What are the regulators of glycogen synthase in liver and muscle?

Back 4

liver: + insulin and glucose, - glucagon and epi
muscle: + insulin, - epi

Front 5

What are the regulators of glycogen phosphorylase in liver and muscle?

Back 5

liver: + glucagon and epi, - insulin
muscle: + epi and AMP, - insulin and ATP

Front 6

What is the immediate precursor to adding a glucose molecule to a glycogen chain?

Back 6

UDP-glucose

Front 7

What is the deficient enzyme of Von Gierke's disease? What are the findings?

Back 7

glucose 6 phosphatase - causes hepatomegaly, severe hypoglycemia with fasting, high blood lactate levels

Front 8

What is the deficient enzyme of Pompe's disease? What are the findings?

Back 8

lysosomal a 1,4 glucosidase - cardiomegaly and systemic findings leading to early death

Front 9

What is the deficient enzyme of Cori's disease? What are the findings?

Back 9

debranching enzyme a 1,6 glucosidase - milder form of Von Gierke's disease

Front 10

What is the deficient enzyme of McArdle's disease? What are the findings?

Back 10

muscle glycogen phosphorylase - increased muscle glycogen, cramps and myoglobinuria with strenuous exercise

Front 11

What is the common denominator of glycogen storage diseases?

Back 11

all result in accumulation of glycogen in cells

Front 12

What is the most common lysosomal storage disease?

Back 12

Gaucher's

Front 13

What is the deficient enzyme and accumulated product in Gaucher's disease?

Back 13

B-glucocerebrosidase causing accumulation of glucocerebroside

Front 14

What is the deficient enzyme and accumulated product of Tay-Sachs disease?

Back 14

hexosaminidase A causing accumulation of GM2 ganglioside

Front 15

What is the deficient enzyme and accumulated product of Niemann-Pick disease?

Back 15

sphingomyelinase causing accumulation of sphingomyelin

Front 16

What is the result of carnitine deficiency?

Back 16

toxic accumulation of long chain fatty acids

Front 17

What is the fuel source for muscle and brain tissue during prolonged starvation?

Back 17

acetoacetate and B-hydroxybutarate

Front 18

What is the rate limiting enzyme in cholesterol synthesis and which drugs inhibit it?

Back 18

HMG-CoA Reductase inhibited by statin drugs

Front 19

What are the essential fatty acids?

Back 19

Linolenic acid and Linoleic acid (arachidonic acid is linoleic acid is absent)

Front 20

What is the function of Apo A1?

Back 20

activates LCAT (lecithin cholesterol acyltransferase)

Front 21

What is the function of Apo B48?

Back 21

mediates chylomicron secretion

Front 22

What is the function of Apo B100?

Back 22

mediates VLDL release, uptake of LDL and IDL

Front 23

What is the function of Apo CII?

Back 23

required cofactor for lipoprotein lipase

Front 24

adult polycystic kidney disease

Back 24

AD mutation of APKD1 gene. always bilateral, presents with massively enlarged kidneys, pain, hematuria, hypertension. associated with berry aneurysms.

Front 25

familial hypercholesterolemia

Back 25

AD: absent or defective LDL receptor causing elevated cholesterol (heterozygotes) or severely elevated cholesterol (homozygotes) resulting in early MI and atherosclerotic disease

Front 26

Marfan syndrome

Back 26

AD mutation of fibrillin. tall stature, long bones, hyperextensible joints, long tapering fingers and toes, dissecting aortic aneurysms, floppy mitral valve, subluxation of lenses

Front 27

Neurofibromatosis type 1 (Von Recklinghausen's disease)

Back 27

AD mutation on chromosome 17. cafe au lait spots, neural tumors, Lisch nodules, skeletal disorders, pheochromocytoma

Front 28

Neurofibromatosis type 2

Back 28

AD mutation of NF2 gene on chromosome 22. bilateral acoustic neuromas, juvenile cataracts.

Front 29

Tuberous sclerosis

Back 29

AD. facial lesions, "ash leaf spots", cortical and retinal hamartomas, seizures, mental retardation, renal cysts, cardiac rhabdomyomas

Front 30

Von Hippel-Lindau disease

Back 30

AD mutation of VHL gene of chromosome 3. hemangioblastomas of retina/cerebrum/cerebellum, half develop bilateral renal cell carcinomas

Front 31

Familial adenomatous polyposis

Back 31

AD mutation of APC gene of chromosome 5. hundreds of polyps cover colon after puberty with 100% progression to colon cancer without resection

Front 32

Huntington's disease

Back 32

AD mutation on chromosome 4. choreiform movements, depression, caudate atrophy, progressive dementia, onset between 20 and 50. Triplet repeat disorder.

Front 33

Hereditary spherocytosis

Back 33

AD. spheroid erythrocytes, hemolytic anemia, increased MCHC, splenectomy is curative.

Front 34

Achondroplasia

Back 34

AD mutation of FGF receptor 3. causes dwarfism - short limbs with normal head and trunk size

Front 35

Cystic fibrosis

Back 35

AR mutation of CFTR gene of chromosome 7. CFTR channel secretes Cl- from lungs and absorbs it from sweat. causes thick mucus production that clogs airways, pancreas and liver. recurrent pulmonary infections, pancreatic insufficiency, increased Cl- in sweat is diagnostic

Front 36

X-linked recessive disorders

Back 36

Bruton's agammaglobulinemia, Wiskott-Aldrich syndrome, Fragile X, G6PD deficiency, Ocular albinism, Lesch-Nyhan syndrome, Duchenne's muscular dystrophy, Hemophilia A & B, Fabry's disease, Hunter's syndrome

Front 37

Duchenne's muscular dystrophy

Back 37

X-linked deletion of dystrophin gene causes accelerated muscle breakdown. weakness of pelvic girdle muscles that moves superiorly. Gower's maneuver, pseudohypertrophy of calf muscles, cardiac myopathy. onset before 5 years of age

Front 38

Becker's muscular dystrophy

Back 38

mutated dystrophin gene. less severe than Duchenne's.

Front 39

Fragile X syndrome

Back 39

X linked defect effecting expression of FMR1 gene. maro-orchidism, large jaw, large ears, mental retardation (2nd most common cause). triplet repeat disorder.

Front 40

What is the 2nd most common cause of mental retardation?

Back 40

Fragile X syndrome

Front 41

What are some trinucleotide repeat disorders?

Back 41

Fragile X, Huntington's, myotonic dystrophy, Friedreich's ataxia

Front 42

Down syndrome

Back 42

Trisomy 21. mental retardation, simian crease, flat facial profile, prominent epicanthal folds, duodenal atresia, congenital heart disease, Alzheimer's disease, increased risk of ALL

Front 43

What is the most common cause of mental retardation?

Back 43

Down syndrome

Front 44

What is the most common chromosomal disorder?

Back 44

Down syndrome

Front 45

Edward's syndrome

Back 45

Trisomy 18

Front 46

Patau's syndrome

Back 46

Trisomy 13