Nucleic Acids (Lecture 29) Flashcards
what is a base?
aromatic ring that differs in the nucleic acid
what is a nucleoside?
base + ribose
what is a nucleotide?
base + ribose + phosphate group
what does glutamine amide contribute to the purine structure?
N3 N9
what does formate contribute to the purine structure?
C2 C8
what does glycine contribute to the purine structure?
C4 C5 N7
what does aspartate amine contribute to the purine structure?
N1
what does HCO3- contribute to the purine structure?
C6
what does aspartate contribute to the pyrimidine structure?
N1 C4 C5 C6
what does glutamine amide contribute to the pyrimidine structure?
N3
what does HCO3- contribute to the pyrimidine structure?
C2
which molecule links to the ribose in a purine?
N9
which molecule links to the ribose in a pyrimidine ?
N1
which orientation is the base put onto the ribose?
beta glycosidic bond (base above)
which stereo conformation re the sugars in nucleic acids
D sugars (furganose conformation)
what it the nucleoside and nucleotide for adenine base?
nucleoside: adenosine
nucleotide: adenylate (AMP)
what it the nucleoside and nucleotide for guanine base?
nucleoside: guanosine
nucleotide: guanylate (GMP)
what it the nucleoside and nucleotide for cytosine base?
nucleoside: cytidine
nucleotide: cytidylate (CMP)
what it the nucleoside and nucleotide for uracil base?
nucleoside: uridine
nucleotide: uridylate (UMP)
what it the nucleoside and nucleotide for thymine base?
nucleoside: deoxythymidine
nucleotide: thymidylate deoxythymidylate (dTMP)
what it the nucleoside and nucleotide for hypoxanthine base?
inosine
inosate (IMP)
what it the nucleoside and nucleotide for xantoine base?
xanthosine
xanthylate (XMP)
what it the nucleoside and nucleotide for orotate (orotic acid) base?
orotidine
orotidylate (OMP)
what is the first step of de novo synthesis of purines?
synthesis of PRPP via alpha-d ribose-5-phosphate and ATP via ribose phosphate pyrophosphokinase (adds 2 phosphates)
the de novo synthesis of purines is regulated at which steps?
synthesis of PRPP
synthesis of 5-phosphoribosylamine
when the cell needs more purines, the amount of PRPP will increase, thus increasing the amount of 5-phosphoribosylamine
what is the committing step in purine de novo synthesis?
PRPP –> 5-phosphoribosylamine
what is the second step of purine de novo synthesis?
PRPP with glutamine form glutamate and beta-5-phosphoribosylamine
pyrophosphate is release, which makes this reaction irreversible
this is done via amidophosphoribosyl transferase
what is the N donor in the second step?
glutamine
why does the release of PPi cause the second step of purine de novo synthesis to be irreversible?
low PPi concentration in the cytosol, because it is always converted into 2Pi, thus making the generation of PPi energetically favourable
what is the usual pathway to donating an amine group?
addition of ATP to a carbonyl group to prime
addition of NH3 and release of Pi
where is the N from glutamine derived from?
side chain
where is the N from aspartic acid derived from?
back bone
