Biochem Flashcards
what amino acids are histones rich in?
lysine and arginine (+ charged)
what ties nucleosome beads together on a string?
H1 (the only histone that is not in a nucleosome core)
What is methylated during DNA replication
template strand cytosine and adenine (allows for mismatch repair)
What inactivates transcription of DNA
histone methylation
What relaxes DNA coiling, allowing for transcription?
histone acetylation
nucleotides with 2 rings
purines (A, G)
nucleotides with 1 ring
pyrimidines (C, U, T)
which nucleotide has a ketone?
guanine
which nucleotide has a methyl?
thymine
what makes uracil?
deamination of cytosine
amino acids necessary for purine synthesis
GAG (glycine, aspartate, glutamate) and THF
nucleoside
base + ribose
nucleotide
base + ribose + phosphate (linked by 3-5 phosphodiester bond)
de novo purine synthesis
start with sugar + PRPP, add base
de novo pyrimidine synthesis
make temporary base (orotic acid), add sugar + PRPP, modify base
what is required for pyrimidine base production
aspartate
what is carbamoyl phosphate involved in?
de novo pyrimidine synthesis and urea cycle
ornithine transcarbamoylase deficiency
accumulation of carbamoyl phosphate, which is then converted to orotic acid; hyperammonemia
hydroxyurea
interferes with nucleotide synthesis, inhibits ribonucleotide reductase
6-MP
blocks de novo purine sunthesis
5-FU
inhibits thymidylatesynthase
methotrexate
inhibits dihydrofolate reductase
trimethoprim
inhibits bacterial dihydrofolate reductase
what is defective in orotic aciduria?
de novo pyrimidine synthesis (can’t convert orotic acid to UMP) because of defect in UMP synthase (phosphoribosyltransferase or orotidine-5-phosphate decarboxylase)