Exam 4 purines, pyrimidines and porphyrins section: things to know Flashcards Preview

Medical Biochemistry > Exam 4 purines, pyrimidines and porphyrins section: things to know > Flashcards

Flashcards in Exam 4 purines, pyrimidines and porphyrins section: things to know Deck (46):
1

Lesch-Nyhan Syndrom

self-mutilating behavior;hyperuricemia; uric acid in urine; low HGPRT activity.

Hyperuricemia caused by decreased purine reutilization.
HGPRT is used to recycle purines

2

methotrexate

folic acid analog; can cause folic acid deficiency; symptoms of weakeness, fatigability, nausea and diarrhea

3

what do you make from inosine

purines, pyrimydines, GMP from XMP
you need inosine to make pyrimidines to make CTP from UTP

4

what inhibits PRPP in purine synthesis?

AMP, IMP, GMP

5

what inhibits phosphoribosylamine? in purine synth.

AMP, IMP, GMP

6

purine synt: what inhibits IMP dehydrogenase

GMP

7

purine synt: what inhibits adenylosuccinate synthetase?

AMP

8

what activates ribonucleotide reductase? what inhibits it ?

ATP; inhibited by dATP

9

crigler-najjar syndrome, type I

jaundice; increased unconjugated bilirubin level in serum, low fecal urobilinogen level; liver biopsy result low activity of enzyme UDP-glucoronyl transferase.

10

gilbert syndrome

jaundice, decreased UDPGT activity. no history of dark colored urine, clay colored stools, abdominal, blood transfusion, illegal drug use. no alcohol compsumption.
high unconjugated bilirubin without other symptoms

11

porphyria cutanea tarda

chronic blistering and scarring of skin when exposed to sunlight; smoker, drinker, worsen his condition. urine and plasma havehigh level of uroporphyrin.
uroporphyrinogen decarboxylase deficiency.

12

acute intermittent porphyria

treat with glucose; intravenous hemin injection to decrease synthesis of hepatic ALAS1.
NOT photosensitive. PBG deaminase defect. PBG and ALA accumulate in urine.
abdominal pain, motor system neuropathies, induced by drugs, alcohol and sun exphsure.

13

regulation of heme synthesis

ALA synthase is rate-limiting. regulated by loevels of heme. inhibit expression of ALAS1, transfer of ALAS1 to mito, catalytic activity of ALAS1.

14

erythropoeitic protoporphyria

deficiency in ferrochetalase

15

role of ferrochelatase

needs ascorbic acid and cysteine. converts protoporphyrin IX into protoheme IX

16

neonatal jaundice

low level lingandin in liver at birth
low hepatic glucuronyl-transferase activity
treat with phototherapy or exchange transfusion
light from fluorescent lamp

17

Gout

pain in big toe, joint pain, alcohol and beef consumption. sodium urate has reduced solubility at lower temperature.

18

primary renal and primary metabolic gout

renal: hyperuricemia caused by underexcretion of uric acid
metabolic: over production of purines and uric acid

19

committed step in biosynthesis of adenine and guanine nucleoside monophosphates is catalyzed by

glutamine-PRPP amidotransferase; inhibited by AMP, GMP and IMP; activated by PRPP

20

allopurinol

inhibits xanthine oxidase

21

pyrimidine nucleotide biosynthesis regulated by allosteric binding of UTP to

ribose 5 phosphate as a substrate

22

folate deficiency leads to decreased rate of synthesis of

amino acids, thymidylate and AMP

23

lead intoxication mechanism

inhibition of enzymes in her RBCs that are present in the mito and in the cytosol. affects ALA dehydratase and ferrochelatase

24

in porphyria cutanea tarda, phlebotomy is used form

reducing iron stores since can be influenced by hepatic iron overload

25

crigler-Najjar syndrome type II

presence of bilirubin monoglucuronide conjugates in urine. UDPGT deficiency is benign. partial deficiency of gene.

26

ALA synthase reaction

glycine to delta-aminolevulinate with pyridoxal phosphate

27

bilirubin formation

hemoglobin to heme, heme to biliverdin, beliverdin to bilirubin

28

what does biliary obstruction cause?

elevated direct/conjugated bilirubin in blood: if blilirubin is conjugated, UDPGT works, so there no deficit, which causes CN I and II and Gilbert syndrom

29

mechanism of methotrexate

inhibits dihydrofolate reductase to suppress synthesis of dTMP and purine nucleotides. antiinflammatory used for RA.

30

why is folate important in treating pernicious anemia?

tetrahydrofolate derivatives are essential for the synthesis of IMP and dTMP in humans.

31

febuxostat mechanism

xanthine oxidase inhibitor

32

colchicine

inhibit microtubule formation and prevents phagocytic cells from engulfing urate crystals. used for gout to alleviate inflammation.

33

uricosuric agents

promote renal clearance of uric acid by inhibiting a urate-anion exchanges that mediates urate re-absorption.

34

how does 5-flurouracil (5-FU) treatment work?

suppresses cell prolieration by inhibiting dTMP (thymidylate) synthesis

35

Adenosine deaminase deficiency

causes immune dysfunction due to accumulation of dATP in body, which is a potent inhibitor of ribonucleotide reductase. treat with bone marryow transplant.

36

chronic hepatitis symptoms

jaundice, mildly protruberant abdomen, high serum levels of indirect bilirubim. disease impairs bilirubin conjugation and thus increases level of unconjugated bilirubin in blood

37

excess unconjugated bilirubin

increased bilirubin formation
defective liver uptake
defective conjugation

38

excess conjugated bilirubin

defective transport to bile
bile duct blockage

39

what is secreted along with urobilinogens that are not absorbed

stercobilin, orange browned colored pigments

40

ALA dehydratase reaction

ALA to PBG; needs zinc; inhibited by lead, can cause anemia and lead poisoning

41

hemolytic anemia

anemia, enlarged spleen, jaundice, blood problem; bizarre looking RBCs, pyruvate kinase deficiency.
disease involved excess bilirubin load because can't metabolize bilirubin or because of hemolytic process.
breakdown of RBCs causes hemolytic jaundice. increased indirect plasma biliruben. increased urobilonogen level in plasma and urine.

42

how does body compensate in pyruvate kinase deficiency?

increase 2,3BPG

43

three types of hyperbilirubinemia

hemolytic anemia: high un/con bili (bile)
hepatitis: high un/con blood)
biliary duct stone: hih unco blood/high con blood

44

why use phenobarbital to treat Crigler-Najjar syndrome type II?

phenobarbital can induce synthesis of hepatic UDP glucuronyl transferase (UDPGT) so that bilirubin conjugation can be stimulated in the patient. won't work for type I.

45

Dubin Johnson syndrome

jaundice no enlarged liver or spleen, no liver failure; abnormally elevated levels of conjugated bilirubin and several liver enzyumes. high coproporphyrin I and III in urine. liver was dark green.
caused by defective transporter for conjugated bilirubin.

46

what causes porphyria cutanea tarda

deficiency in urophorpyrinogen decarboxylase. uroporphyrin accumulates in urine and patients are photosensitive.