biochem

Question 1

deamination of cytosine

take off NH2

Answer 1

uracil

Question 2

CG vs AT bond

Answer 2

CG triple bond. highger temp to break

Question 3

cofactors to make carbamoyl phosphate

Answer 3

glutamine
CO2
ATP

Question 4

carbamoyl phosphate is in what pathway

Answer 4

making pyrimidine and purines

Question 5

what enzyme makes carbamoyl phosphate

Answer 5

CPS II

Question 6

rate limiting pyrimidine synthesis

Answer 6

CPS II

Question 7

where is CPS II

Answer 7

cytosol

Question 8

to make Uridine mono phosphate (pyrimidine synthesis)

Answer 8

PRPP plus orotic acid

Question 9

name the enzymes in pyrimidine synthesis

Answer 9

CPSII- rate limiting
ribonucleotide reductase
thymidylate synthase (needs THF aka folic acid)

Question 10

What inhibits dihydrofolate reductase

Answer 10

Trimethoprim in prokaryotes

MTX in eukaryotes

Question 11

Orotic aciduria biochem defect

Answer 11

defect in UMP synthase

auto recessive

Question 12

orotic aciduria clinical picture from UMP synthase

Answer 12

high orotic acid
not high ammonia (like in OTC)
failure to thrive at young age
megaloblastic anemia

Question 13

main step and rate limiting in purine synthesis

Answer 13

PRPP to IMP

enzyme: glutamine PRPP amidotransferase

Question 14

what inhibits glutamine PRPP amidotransferase

Answer 14

6 Mercaptopurine

Question 15

What drugs inhibit enzymes in pyrimidine synthesis

Answer 15

5-FU- thymidilate synthase
MTX- DHF reductase
TMP- DHF reductase
hydroxy urea- ribonucleotide reductase

Question 16

what drugs inhibit enzymes in purine synthesis

Answer 16

6 mercaptopurine- PRPP amidotransferase

Mycophenolate- IMP dehydrogenase

Question 17

which enzyme is used to add phosphates onto bases to recycle the nucleobases?

Answer 17

HGPRT

Question 18

clinical features lesch nyhan

Answer 18

gout
mental retardation
aggressive
self mutilation
choreoathetosis

Question 19

syndrome with ineffective adenosine deaminase

Answer 19

SCID

Question 20

what pathway is affected in SCID

Answer 20

recycling purines

Question 21

clinical picture SCID

Answer 21

severe recurrent infections
-candidiasis
-pneumocystis pneumonia
chronic diarrhea
failure to thrive
No thymic shadow!!!!