Usmle Step 1 Biochemistry Part 1

Front 1

Deficient enzyme in Phenylketonuria (PKU)

Back 1

Phenylalanine hydroxylase (PAH)

Front 2

PKU presentation?

Back 2

Seizures, albinism and a "musty odor" to the baby's sweat and urine. If untreated develops microcephaly and impairment of cerebral function.

Front 3

PKU Gene?

Back 3

PAH gene is located on chromosome 12 in the bands 12q22-q24.1

Front 4

What does phenylalanine hydroxylase do?

Back 4

Converts the amino acid phenylalanine into the amino acid tyrosine

Front 5

PKU treatment?

Back 5

special diet low in phenylalanine

Front 6

Why consuming alcohol in a fasting state can make you hypoglycemic?

Back 6

Because alcohol metabolism changes the NADH/NAD+ ratio. Important steps in gluconeogenesis use NAD+.

Front 7

Fatty liver mechanism in kwashiorkor?

Back 7

Low protein intake leads to reduced production of VLDLs thus accumulating fatty acids within the liver.

Front 8

Edema, irritability, anorexia, ulcerating dermatoses, and an enlarged fatty liver. Kwashiorkor or Marasmus?

Back 8

Kwashiorkor

Front 9

Tissue and muscle wasting and variable edema. Kwashiorkor or Marasmus?

Back 9

Marasmus

Front 10

Alcoholic develops a rash, diarrhea and altered mental status. What is the most likely cause?

Back 10

Vitamin B3 deficiency

Front 11

Enzyme deficient in Alkaptonuria?

Back 11

homogentisate 1,2-dioxygenase

Front 12

Black spots in the sclera of the eye and urine turns brown when left exposed to open air. Name the disease.

Back 12

Alkaptonuria

Front 13

What accumulates in Alkaptonuria?

Back 13

homogentisic acid in tissues

Front 14

What does homogentisate 1,2-dioxygenase do?

Back 14

Catalyzes the conversion of homogentisate to 4-maleylacetoacetate. Involved in the break down of the amino acids tyrosine and phenylalanine.

Front 15

Distinctive characteristic of _________ is that ear wax exposed to air turns red or black after several hours because of the accumulation of homogentisic acid.

Back 15

Alkaptonuria

Front 16

Genetic disorder characterized by high cholesterol levels, specifically very high low-density lipoprotein (LDL)

Back 16

Familial hypercholesterolemia

Front 17

What disease is caused by a mutation of the LDLR gene that encodes the LDL receptor protein?

Back 17

Familial hypercholesterolemia

Front 18

Common places cholesterol accumulates in patients with Familial hypercholesterolemia?

Back 18

Eyelids (xanthelasma palpebrarum), the outer margin of the iris (arcus senilis corneae) and in the form of lumps in the tendons of the hands, elbows, knees and feet, particularly the Achilles tendon (tendon xanthoma).

Front 19

Can Familial Hypercholesterolemia lead to atherosclerosis?

Back 19

Yes.

Front 20

Enzyme deficient in McArdle’s disease?

Back 20

myophosphorylase

Front 21

Exercise intolerance with myalgia, early fatigue, painful cramps, weakness of exercising muscles and myoglobinuria. Name the disease.

Back 21

McArdle's disease.

Front 22

McArdle's disease treatment?

Back 22

Vitamin B6 appears to impart greater resistance to fatigue.

Front 23

What does Myophosphorylase do?

Back 23

Involved in the breakdown of glycogen to glucose for use in muscle. Removes 1,4 glycosyl residues from outer branches of glycogen and adds phosphate to form glucose-1-phosphate.

Front 24

Chronic pancreatitis with pancreatic insufficiency. What vitamins are likely deficient?

Back 24

A,D,E,K

Front 25

What are the fat soluble vitamins?

Back 25

A,D,K,E

Front 26

What are the water soluble vitamins?

Back 26

Vitamin C, Thiamine (B1), Riboflavin (B2), Niacin (B3), Pantothenic Acid, Biotin, Folate, Cobalamin (B12), Pyridoxine (B6)

Front 27

Higher toxicity. Water or fat soluble vitamins?

Back 27

Fat soluble vitamins because they accumulate in fats.

Front 28

Which B vitamin is stored in the liver?

Back 28

B12

Front 29

Vitamin A (retinol) deficiency.

Back 29

Night blindness, dry skin

Front 30

Vitamin B1 (thiamine) deficiency.

Back 30

Beriberi and Wernicke-Korsakoff syndrome.

Front 31

Weight loss, emotional disturbances, impaired sensory perception, weakness and pain in the limbs, and periods of irregular heart rate.

Back 31

Beriberi

Front 32

Folic acid deficiency.

Back 32

Microcytic megaloblastic anemia,

Front 33

Biotin deficiency?

Back 33

Dermatitis, enteritis. Caused by antibiotic use and ingestion of raw eggs.

Front 34

Vitamin C (ascorbic acid) deficiency?

Back 34

scurvy, anemia, bruising, poor wound healing.

Front 35

Vitamin D deficiency?

Back 35

Rickets in children, osteomalacia in adults and hypocalcemic tetany.

Front 36

Vitamin E deficiency?

Back 36

Increased fragility of erythrocytes, neurodysfunction.

Front 37

Vitamin K deficiency?

Back 37

Hemorrhage

Front 38

zinc deficiency?

Back 38

Delayed wound healing, hypogonadism.

Front 39

3 D's: Dermatitis, Diarrhea, Dementia.

Back 39

Pellagra.

Front 40

Vitamin B2 (riboflavin) deficiency?

Back 40

Angular stomatitis, Cheilosis, corneal vascularization.

Front 41

Vitamin B3 (niacin) deficiency?

Back 41

Pellagra.

Front 42

Vitamin B5 (pantothenate) deficiency?

Back 42

Dermatitis, enteritis, alopecia, adrenal insufficiency.

Front 43

Vitamin B6 (pyridoxine) deficiency?

Back 43

Convulsions, hyperirritability, peripheral neuropathy.

Front 44

Vitamin B12 (cobalamin) deficiency?

Back 44

Microcytic megaloblastic anemia, neurologic symptoms, glossitis.