Usmle Step 1 Random Facts

Front 1

Which enzyme is the rate limiting step for glycolysis?

Back 1

Phosphofructokinase-1

Front 2

Which enzyme is the rate limiting step for gluconeogenesis?

Back 2

Fructose-1,6-biphosphate

Front 3

Which enzyme is the rate limiting step for the TCA cycle?

Back 3

Isocitrate dehydrogenase

Front 4

Which enzyme is the rate limiting step for glycogen synthesis?

Back 4

Glycogen synthase

Front 5

Which enzyme is the rate limiting step for glycogenolysis?

Back 5

Glycogen phosphorylase

Front 6

Which enzyme is the rate limiting step for the HMP shunt?

Back 6

G6PD

Front 7

Which enzyme is the rate limiting step for de novo pyrimidine synthesis?

Back 7

Carbamoyl phosphate synthetase II

Front 8

Which enzyme is the rate limiting step for de novo purine synthesis?

Back 8

Glutamine-PRPP-amidotransferase

Front 9

Which enzyme is the rate limiting step for the urea cycle?

Back 9

Carbamoyl phosphate synthetase I

Front 10

Which enzyme is the rate limiting step for fatty acid synthesis?

Back 10

Acetyl-CoA-carboxylase

Front 11

Which enzyme is the rate limiting step for fatty acid oxidation?

Back 11

Carnitine acyltransferase I

Front 12

Which enzyme is the rate limiting step for ketogenesis?

Back 12

HMG CoA synthase

Front 13

Which enzyme is the rate limiting step for cholesterol synthesis?

Back 13

HMG-CoA reductase

Front 14

What is the mnemonic for the gycogen storage diseases?

Back 14

Very Poor Carbohydrate Metabolism

Front 15

Which enzyme is deficient in Von Gierke's disease (type I)?

Back 15

Glucose-6-phosphotase; severe fasting hypoglycemia, increased glycogen in the liver, increased blood lactate and hepatomegaly.

Front 16

Which enzyme is deficient in Pompe's disease (type II)?

Back 16

Lysosomal a-1,4-glucosidase; cardiomegaly and systemic findings

Pompe's trashes the Pump (heart liver and muscle)

Front 17

Which enzyme is deficient in Cori's disease (type III)?

Back 17

Debranching enzyme (a-1,6-glucosidase); milder form of type I with normal blood lactate levels; gluconeogenesis is intact

Front 18

Which enzyme is deficient in McArdle's disease (type V)?

Back 18

Skeletal muscle glycogen phosphorylase; increased glycogen in muscle, but cannot break it down, leading to painful muscle cramps and myoglobinuria with exercise.

McArdles = Muscle

Front 19

Which enzyme is deficient in the lysosomal storage disorder Fabry's disease?

Back 19

a-galactosidase A; peripheral neuropathy of hands/feet, cardiovascular and renal disease, X-recessive.

Front 20

Which enzyme is deficient in the lysosomal storage disorder Gaucher's disease?

Back 20

Glucocerebrosidase; hepatosplenomegaly, aseptic necrosis of femur, Gaucher's cells (look like crumpled tissue paper). A-recessive

Front 21

Which enzyme is deficient in the lysosomal storage disorder Neimann-Pick disease?

Back 21

Sphinomyelinase; neurodegeneration, cherry red spot on macula, foam cells, A-recessive.

Front 22

Which enzyme is deficient in the lysosomal storage disorder Tay-Sachs disease?

Back 22

Hexosaminidase A; neurodegeneration, cherry red spot on macula, onion-skinned lysosomes, NO hepatosplenomegaly, A-recessive

Front 23

Which enzyme is deficient in the lysosomal storage disorder Krabbe's disease?

Back 23

B-galacocerebrosidase; peripheral neuropathy, optic atrophy, globoid cells, A-recessive

Front 24

Which enzyme is deficient in the lysosomal storage disorder Metachromatic Leukodystrophy?

Back 24

Arylsulfatase A; central and peripheral demyelination with ataxia and dementia; A-recessive.

Front 25

Which enzyme is deficient in the lysosomal storage disorder Hurlers' syndrome?

Back 25

a-L-iduronidase (accumulates heparin.dermatan sulfate); gargoylism, airway obstruction, corneal clouding, hepatosplenomegaly, A-recessive

Front 26

Which enzyme is deficient in the lysosomal storage disorder Hunter's syndrome?

Back 26

Iduronate sulfatase; Mild Hurler's + aggressive behavior, no corneal clouding, X-recessive

Front 27

Mnemonic for Neiman-Pick, Tay-Sachs and Hunters:

Back 27

No man picks (Neimann-Pick) his nose with his sphinger (sphingomyelinase).

Tay-SaX (tay-sachs) lacks heXosaminidase.

Hunters see clearly (no corneal clouding) and aim for the X (X-recessive).

Front 28

At what stage are primary oocytes held until ovulation?

Back 28

Prophase of meiosis I.

Front 29

At what stage of meiosis II is an egg released during ovulation?

Back 29

Metaphase

Front 30

Complete mole:

Back 30

Normal 46XX karyotype; results from fertilization of an empty egg with a haploid 23X sperm. Complete moles are characterized by generalized edema of chorionic villi forming grape-like transparent vesicles and an absence of a fetus.

Partial moles are usually triploid (69XXX or 69XXY) due to fertilization of an egg with two sperm.

* Preeclampsia during first trimester, MASSIVELY elevated hCG levels.

Front 31

Derivatives of pharyngeal arch 1:

Back 31

Cranial nerve V
Muscles of mastication
Maxilla, Mandible, Malleus, Incus

Front 32

Derivatives of pharyngeal arch 2:

Back 32

Cranial nerve VII
Muscles of facial expression.
Stapes.

Front 33

Derivatives of pharyngeal arch 3:

Back 33

Cranial nerve IX
Common carotid and internal carotid arteries.

Front 34

Derivatives of pharyngeal arch 4:

Back 34

Cranial nerve X
Muscles of soft palate, muscles of the pharynx, right subclavian artery, arch of aorta.

Front 35

Derivatives of pharyngeal arch 6:

Back 35

Cranial nerve X (recurrent part).
Muscles of larynx, upper muscles of esophagus, pulmonary arteries, ductus arteriosus.

Front 36

Derivatives of the pharyngeal pouches:

Back 36

1 - epithelial lining of auditory tube and middle ear cavity.
2 - epithelial lining of palatine tonsil crypts
3 - inferior parathyroid glands, thymus
4 - superior parathyroid gland

Front 37

Differences between a direct and an indirect inguinal hernia:

Back 37

Front 38

What is the difference between Erb's and Klumpke's palsy?

Back 38

Erb's palsy is an adduction injury to the upper brachial plexus, whereas Klumpke's palsy is an abduction injury to the lower brachial plexus that may involve the sympathetic chain at T1 producing Horner's syndrome.