Chapter 18

Describe the four biochemical processes that nucleotides participate in. Give examples of nucleotides - other than those containing the nucleotide base adenine- that have a role in each of these processes.

Nucleotide salvage pathways are an important recycling process in cells because they require less ATP than the de novo biosynthetic pathways use. What is the source of most nucleotide bases salvaged by recycling processes in cells?

What is a purinosome, and what is the experimental evidence for the existence of purinosomes in cells? What biochemical methods could be used to "prove" the existence of purinosomes in cells under normal physiologic conditions?

What regulatory mechanisms ensure a balanced pool of guanine and adenine in cells?

What is the primary metabolic fate of excess purine nucleotides in humans, Siberian tigers, flamingos, rattlesnakes, tuna, great white sharks, salamanders, cockroaches, and lobsters?

What is the biochemical basis for ADA-SCID, and what are the treatment options for patients diagnosed with ADA-SCID?

Describe similarities and differences between the regulation of the de novo pyrimidine biosynthetic pathway in \(E .\) coli compared to that in humans.

How would a deficiency in the human enzyme dihydropyrimidine dehydrogenase cause 5 -fluorouracil toxicity in cancer patients undergoing chemotherapy?

Describe the RNA world hypothesis. What is the best evidence to date that this view of early biochemical life on Earth may be accurate?

Describe the function and regulation of \(E .\) coli ribonucleotide reductase.

What are three sources of deoxyuridylate in bacterial cells?

Describe three mechanisms of methotrexate drug resistance in human cancer cells.