Kaplan Biochem Exam 1

Question 1

catecholamine synthesis intermediates, steps (4)

Answer 1

tyrosine –> L dopa –> dopamine –> norepinephrine –> epinephrine

Question 2

rate limiting step in catecholamine synthesis

Answer 2

tyrosine hydoxylase: tetrahydrobiopterin (THB) conversion of tyrosine to l topa

Question 3

conversion of norepi to epi

Answer 3

accomplished by PNMT (phenylethanolamine-N-methyltransferase)

Question 4

PNMT: its importance

Answer 4

cortisol stimulates expression of PNMT gene to catalyze norepi to epi, which is more potent

Question 5

how does PNMT work?

Answer 5

transfers a methyl group form norepi to epi. involves S-adenosyl methionine transferase (SAM)

Question 6

homocystinuria

Answer 6

autosomal recessive disorder

cystathionine beta synthase (CBS) deficiency impairs cystathionine sythensis and results in elevated serum levels of homocysteine

Question 7

autosomal recessive disorder, maradinoid habitus, bilateral lens disclocation

Answer 7

homocystinuria - deficiency of

cystathionnine beta synthase (CBS)

or

methionine synthase deficiency

or

5,10-THF reductase deficiency ca

Question 8

calcium bilirubinate stone

Answer 8

indicates extravascular hemolysis (sickle cell dx or hereditary spherocytosis)

Question 9

calcium oxalate stones and cystine stones

Answer 9

kidney stones rather than gallstones

Question 10

yellow gallstones

Answer 10

cholesterol

Question 11

brown mixed stones

Answer 11

billiary tract infection

Question 12

predisposes affected individuals to hemolysis in the presence of oxidizing agents

Answer 12

G6PD deficiency: x linked recessive dx, most common RBC enyzme disorce, confers protection against malaria

G6PD is the only source of NADPH in the RBC: protects membrane proteins and lipids from damage by reactive oxygen species (ROS).

Question 13

neonate with enlarged spleen and chronic hemolysis

Answer 13

pyruvate kinas deficiency

Question 14

neonate with direct hyperbilirubinemia

Answer 14

billary atresia

Question 15

infant with acute swelling and pain in extremities and chronic anemia

Answer 15

sickle cell dz- pt presents with dactylitis, pain in hands and feet

Question 16

hydroxymethylbilane synthase

Answer 16

also known as porphobilinogen deaminase PBGD