USMLE Flashcards
(39 cards)
Purines
Pure AG
A
G
Pyrimidines
CUT the PY
C
U
T
Amino acid requirement for purine synthesis
GAG
Glycine
Aspartate
Glutamine
Amino acid requirement for both purine and pyrimidine synthesis
Aspartate
MOA of
MTX
TMP (trimethoprim)
Pyrimethamine
Inhibit dihydrofolate reductase
MTX - humans
TMP - bacteria
Pyrimethamine - protozoans
(pyrimidine synthesis)
MOA of 5-FU
Inhibits thymidylate synthase
pyrimidine synthesis
MOA of
6-MP and azathioprine
Inhibit de novo purine synthesis
MOA of hydroxyurea
Inhibits ribonucleotide reductase
purine and pyrimidine synthesis
Lesch-Nyhan syndrome absent enzyme
HGPRT
leads to: Hyperuricemia Gout Pissed off (aggression and self-mutilation) Retardation T (dysTonia)
Unambiguous genetic code features
Each codon specifies only 1 amino acid
Degenerate or redundant genetic code features
Most AA are coded by multiple codons
EXCEPT:
Methionine - AUG (MET tayo in AUG)
Tryptophan - UGG
Transition mutation
Purine to purine
Pyrimidine to pyrimidine
Transversion mutation
Purine to pyrimidine
Pyrimidine to purine
Most severe mutation
Frameshift
Frameshift > nonsense > missense»_space; silent
Missense mutation
Changed AA
Sickle cell dse (glutamate to valine)
Sick GV
Nonsense mutation
Early stop codon
Nonfunctional protein
Stop this nonsense!
Frameshift mutation
Deletion or insertion of nucleotides not divisible by 3
Leads to misreading of downstream nucleotides
Duchenne muscular dystrophy
Tay-Sachs dse
Rate limiting enzyme of
Glycolysis
Phosphofructokinase-1 (PFK-1)
Rate limiting enzyme of
Gluconeogenesis
Fructose-1,6-bisphosphatase
Rate limiting enzyme of
TCA cycle
Isocitrate dehydrogenase
Rate limiting enzyme of
Glycogenesis
Glycogen synthase
Rate limiting enzyme of
Glycogenolysis
Glycogen phosphorylase
Rate limiting enzyme of
HMP shunt
G6PD
Rate limiting enzyme of
De novo pyrimidine synthesis
Carbamoyl phosphate synthetase II
