13 terms

Final: Nitrogen Metabolism II

What is related to nitrogen metabolism and arises from very simple starting compounds?
Nucleotide biosynthesis. Two of the nitrogens of purines come from the amine of glutamine; one comes from incorporation of glycine, and one from aspartate.
Why is the synthesis of nucleotides carefully balanced in cells?
Imbalances in quantity of nucleoteides is a factor in causing mutations.
What types of phosphates in purine nucleotides inhibit synthesis?
Mono, di, and triphosphates.
T/F: IMP is not intermediate that is at the branch point between synthesis of AMP and GMP.
False it is an
List some ways in which a cell "balances" the control of purine levels.
AMP requires GTP for energy. AMP also inhibits its own synthesis by feedback inhibition. Synthesis of GMP requires ATP for energy and GMP feedback inhibits its own synthesis as well.
What do specific kinases, such as AMP kinase, convert?
Nucleoside monophosphates (such as AMP) to nucleoside diphosphates (such as ADP).
What converts Nucloside diphosphates to nucleoside triphosphates?
These are catalyzed by nucleoside diphosphokinase (NDPK). NDPK also converts all of the deoxyribonucleoside diphosphates to corresponding deoxyribonucleoside triphosphates.
T/F: PUrine breakdown (catabolism) goes through the intermediate Xanthine, which is broken down to uric acid and ultimately to glyoxylate and urea.
True. Also, Uirc acid crystals are the causes of the painful disease known as gout.
What is the primary regulatory enxypme of pyrimidine biosynthesis?
ATCase. It provides balance between purines and pyrimidines, since it is activated by a purine (ATP) and inactivated by a pyrimidine (CTP).
Amino acides are precursors to what?
Prymidine synthesis. The first prymidine nucleotide made up is UMP, and from it UDP, UTP, and CTP are made.
T/F: Deoxyribonucleotides (the building blocks of DNA) are not made up from ribonucleotides (building blocks of RNA_ using the enzyme ribonucleotide reductase (RNR).
False. Note that the precursor ribonucleotides are DIPHOSPHATES and that the reaction simple reduces the hydroxyl group on the ribose ring to a hydrogen, thus making deoxyribose as the sugar on a deoxyribonucleotide.
Thymidine nucleotides are made from what?
Uridine nucleotides.
List the process that forms Hymidine nucleotides.
UDP goes to dUDP. Then, several reactions later, dTTP is made.