Chapter 32 Flashcards
what are amino acids precursors to?
immune system signals
hormones
membrane lipid constituents
electron carriers
nucleotide bases
what are the two ways nucleotides can be synthesized?
de novo
salvage pathways
what is de novo nucleotide synthesis?
purines and pyrimidines are made by scratch
energy source necessary
shut off if body can salvage
what is the salvage nucleotide synthesis pathway?
preformed bases are recovered and attached to an activated ribose
uses less energy
what are pyrimidines synthesized from?
bicarbonate, aspartate, and ammonia, with glutamate often serving as the nitrogen donor
in what order of pyrimidines synthesized?
the pyrimidine ring is synthesized first and then attached to an activated ribose
how are nucleoside monophosphates converted into diphosphates?
by specific nucleoside monophosphate kinases
EX: UMP Kinase forms UDP from UMP
what do nucleoside diphosphate kinases do?
they catalyze the interconversion of di - and triphosphates
how are purines synthesized?
purines are synthesized on a ribose molecule in the de novo pathway
(synthesized on the PRPP)
ring is built second
what does the initial committed step of purine synthesis form?
5-phosphoribosyl-1-amine from PRPP and glutamine
(the amine is in the beta configuration)
how are deoxyribonucleotides synthesized?
from ribonucleoside diphosphates
the 2’-hydroxyl group of ribose is replaced by a hydrogen atom in a reaction catalyzed by ribonucleotide reductase
what activates ribonucleotide reductase?
ATP
what does ribonucleotide reductase do?
it catalyzes the synthesis of deoxyribonucleotides by reducing ribonucleoside diphosphate to deoxyribonucleoside diphosphate
what are the products of ribonucleotide reductase?
ADP ⇒ dADP
GDP ⇒ dGDP
CDP ⇒ dCDP
UDP ⇒ dUDP
what does further processing of the products of ribonucleotide reductase do?
dADP ⇒ dATP
dGDP ⇒ dGTP
dCDP ⇒ dCTP
dUDP ⇒ TTP
what does ATP do in the regulation of ribonucleotide reductase?
activates
signals high energy changes
what does dATP do in the regulation of ribonucleotide reductase?
it inhibits
how are deoxy substrates regulated?
they regulate each other ⇒ balance
how is TMP synthesized?
a methyl group is added to dUMP
