Biochem from UWorld

Question 1

ricin

Answer 1

cleaves rRNA of 60S subunit

Question 2

7a-hydroxylase

Answer 2

cholesterol to bile acids

Question 3

Gs

Answer 3

glucagon, TSH, and PTH receptors

Question 4

Bohr effect

Haldane effect

Answer 4

peripheral tissues

lungs

Question 5

scurvy also causes

Answer 5

anemia

hyperkeratotic papular rashes

Question 6

pyruvate carboxylase regulation

Answer 6

acetyl CoA stimulates

gluconeogenesis

Question 7

insulin resistance

Answer 7

aberrant serine or threonine phosphorylation of IRS-1 via TNFa, catecholamines, glucocorticoids, or glucagon

Question 8

CN poisoning

Answer 8

flush, RR, HR, headache, N/V, then resp/cardiac dysfunction

binds cytochrome a-a3 complex

trapped by methemoglobin induced by amyl nitrates, or can use sodium thiosulfate to make thiocyanate which is excreted in urine

Question 9

heme to biliverdin

Answer 9

heme oxygenase

Question 10

heme synthetic enzymes

Answer 10

ferrochetalase

uroporphrinogen decarboxylase

Question 11

treat homocystinuria

Answer 11

B6

decrease methionine

Question 12

PMNT

Answer 12

NE to E

under control of cortisol

Question 13

treat orotic aciduria

Answer 13

uridine to inhibit CPS I

Question 14

enolase

Answer 14

2PG to PEP

Question 15

aconitase

Answer 15

citrate to isocitrate

Question 16

hemoglobin C

Answer 16

Glu –> Lysine (more positive)

Question 17

aging

Answer 17

less production of dermal collagen and elastin

Question 18

heme synthesis

Answer 18

Succinyl CoA + glycine + B6 —ALAS–> ALA —ALA dehydratase–> porphyrobilinogen —HMB synthase—> HMB (UPI) —Uroporphyrinogen III synthase–> uroporphyrinogen III —UPDC—> Coporphrinogen III —CPO—> protoporphyinogen IX —> protoporphyrin IX —Ferrochetalase+Fe–> Heme

Question 19

Heme regulatory

Answer 19

Lead —] ALA dehydratase
Lead —] ferrochetalase
Heme, glucose —-] ALA synthase
Alcohol, barbiturates, hypoxia —> ALA synthase

Question 20

high glycogen in lysosomes

Answer 20

Pompe (acid maltase/a-glucosidase)

Question 21

sorbitol dehydrogenase

Answer 21

sorbitol –> fructose

Question 22

dihydropterin reductase deficiency

Answer 22

can’t do BH2 to BH4

needed for phenylalanine hydroxylase and tyrosine hydroxylase

Question 23

nitrous acid

Answer 23

deaminates C, A, G

Question 24

glycogen phosphorylase kinase

Answer 24

active when phosphorylated by PKA
active when allosteric Ca binding
activates glycogen phophorylase

Question 25

JAK-STAT

Answer 25

CSF's, GH, prolactin, IL2, cytokines

Question 26

GLUT

Answer 26

1 - RBC, BBB = basal 2 - liver, beta cells, renal tubular, SI = regulate 3 - placenta, neurons 4 - skeletal muscle, adipocytes = insulin 5 - sperm, GI tract = fructose

Question 27

elastin

Answer 27

desmosine cross-linking via lysyl hydroxylase on four chains glycine, alanine, valine fewer hydroxylated proline, lysine

Question 28

2,3-DPG

Answer 28

stabilizes T form (no O2) | facilitates release at tissue level

Question 29

Xeroderma pigmentosum

Answer 29

often from UV-specific endonuclease deficiency

Question 30

methylmalonic acidemia

Answer 30

defect in isomerization of methylmallonyl CoA to succinyl CoA

Question 31

GTP made in glycolysis

Answer 31

succinyl-CoA synthetase/succinate thiokinase

Question 32

GTP used

Answer 32

PEPCK

Question 33

folate

Answer 33

thymidylate synthase

Question 34

need CoA

Answer 34

OAA to citrate vit A, D, cholesterol, steroids, heme A FA, AA, protein

Question 35

proprionic acid

Answer 35

catabolite of Ile, Val, Thr, Met, cholesterol, odd chain FA

Question 36

OATP MRP2

Answer 36

passive uptake indirect bili to liver active secretion direct bili into bile

Question 37

heme synthesis

Answer 37

in mitochondria

Question 38

pancreatic B cell regulation

Answer 38

Glucose enters, increase ATP via TCA, leads to closure of K channel, depolarize, Ca channel open, insulin out

Question 39

can't use ketone bodies

Answer 39

RBC (no mitochondria) | Liver (no succinyl-CoA-acetoacetate CoA transferase)

Question 40

lead poisoning mechanism

Answer 40

affinity for sulfhydryl groups of delta-ALA-dehydratase and ferrochetalase delta-ALA = succinyl CoA + glycine with B6

Question 41

N-acetylglutamate

Answer 41

glutamate + acetylCoA, needed for CPS I

Question 42

Hexokinase

Answer 42

can save fructose in fructokinase def

Question 43

G6PDH

Answer 43

G6P to 6PG

Question 44

prevent tumor lysis syndrome

Answer 44

rasburicase (inhibits urate oxidase) | allopurinol

Question 45

metabolized faster than glucose

Answer 45

fructose | aldolase B yields DHAP and glyceraldehyde bypassing PFK1

Question 46

chronic myeloproliferative disorders

Answer 46

polycythemia vera essential thrombocytosis primary myelofibrosis V617F mutation in JAK2