Nucleotide Metabolism Flashcards
What is illustrated by the Central Dogma of Molecular Biology?
The Central Dogma illustrates the major processes involved in the handling of genetic information.
What is DNA replication?
Process in which DNA molecules are replicated. Upon cell division, each daughter cell receives a copy of the original information found in the parental cell and uses this template to form a complementary strand.
What is transcription?
Process in which the transfer of information found in the dsDNA to the base sequence of an ssRNA.
(This is the first stage in the expression of genetic information.)
What is translation?
If the RNA is mRNA, then this process coverts the information in the RNA base sequences to the amino acid sequence of a protein.
What is reverse transcription?
In the life cycle of retroviruses, this process is used to synthesize DNA from the information in their RNA genomes.
What is repair?
Process in which damaged DNA is mended.
What is recombination?
Process in which rearrangements of genetic material are produced.
What are mutations?
Occasional mistakes in any of the processes.
What are the raw materials for evolution?
Mutations
What is the purpose of the chemical properties of amino acids?
To direct the three-dimensional folding of the protein molecule and the assembly of subunits into active molecules.
What often undergo extensive processing?
Nucleic acids and proteins
What is under careful regulation?
The expression of genetic information
What are the three pathways associated with purines and pyrimidines?
- ) De Novo biosynthesis - made from new molecules
- ) Salvage synthesis - made from recycled parts
3) Degradation - breakdown when no longer needed
How does De Novo Purine Biosynthesis start?
De Novo Purine Biosynthesis starts with pentose sugar and then slowly builds the purine ring.
What is Step 1 of De Novo Purine Biosynthesis?
Step 1 is regulated, but not committed.
Alpha Ribose5P uses PRPP synthetase and ATP to for PRPP.
Negative Feedback - Purine nucleotides inhibit PRPP synthetase.
What is Step 2 of De Novo Purine Biosynthesis?
Step 2 is regulated and committed.
PRPP uses PRPP glutamyl amido transferase and glutamine to form 5-Phosphoribosylamine.
Negative feedback - Purine nucleotides inhibit PRPP glutamyl amido transferase.
Positive feedback - PRPP activates PRPP glutamy amido transferase.
What steps of De Novo Purine Biosynthesis involve glutamine?
(2) PRPP uses PRPP glutamyl amido transferase and glycine to for 5-Phosphoribosylamine.
(5) Formylglycinamide ribosyl5P uses ATP and glutamine to form Formylglycinamidine.
(15) Xanthosine monophosphate (UMP) uses ATP and glutamine to form Guanosine monophosphate (GMP)
What steps of De Novo Purine Biosynthesis involve folate derivatives?
(4) Glycinamide ribosyl5P uses formyl transferase and folate to form Formylglycinamide ribosyl5P.
(10) Aminoimidazolecarboxamide ribosyl5P uses transformylase and folate to form Amidoimidazolecarboxymide ribosyl phosphate.
What are the origins of residues of the purine ring?
- Start at top N on big ring, N = Aspartate
- Go counter clockwise around ring, C = Formate
- N = Amide N of Glutamine
- and 5. C = Glycine
- C = CO2
- Start at top N on little ring, N = Glycine
- Go clockwise, C = Formate
- N = Amide N of Glutamine
What are the inhibitors of De Novo Purine Biosynthesis?
Block steps 2, 5, 15:
Glutamine analogs like Azaserine are similar in structure to glutamine but not enough to continue the reaction. (Azaserine is too toxic to use in humans.)
What are the inhibitors of folate metabolism?
Block steps 4, 10:
Sulfonamides and Methotrexate are competitive antagonists in folate metabolism.
How do sulfonamides inhibit folate metabolism?
Bacteria synthesize folic acid from para amino benzoic acid (PARA). Sulfonamides are PABA analogs (competitive antagonists) and inhibit synthesis of folic acid in susceptible bacteria.
How does Methotrexate inhibit folate metabolism?
Bacteria and human use Dihydrofolate reductase to add 4 Hs to Folic Acid and form Tetrahydrofolate.
Methotrexate is a folate analog (competitive antagonist) that inhibits Dihydrofolate reductase and prevent the formation of Tetrahydrofolate. It is used in cancer chemotherapy.