Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
67 Cards in this Set
- Front
- Back
|
Name the five major purines.
|
Adenine
Guanine Hypoxanthine Xanthine Uric acid |
|
|
Name the four major pyrimidines.
|
Cytosine
Thymine Uracil Orotic acid |
|
|
What is the name of a hyposanthine ring and a ribose sugar?
|
Inosine
|
|
|
On what position on the ribose sugar will the base attach?
|
1'
|
|
|
On what position on the ribose sugar will you deoxydize?
|
2
|
|
|
Name the contributors to the purine ring structure.
|
2 Gln
2 THF 1 CO2 1 Asp 1 Gly |
|
|
Name the contributors to the pyrimidine ring structure?
|
1 Asp
1 Gln 1 CO2 |
|
|
Under what conditions will nucleotide synthesis continue?
|
Well fed
High energy charge High amino acid |
|
|
What enzyme is the first regulatory step towards nucleotide synthesis?
|
pyrophosphoribosyl kinase (PPR-kinase)
|
|
|
What will inhibit pyrophosphoribosyl kinase?
|
low energy charge (high ADP and GDP)
|
|
|
What does pyrophosphoribosyl kinase make? From what substrate? What is the cost?
|
PRPP
Ribose-5-P 2 ATP (ATP to AMP) |
|
|
What is the first addition to the PRPP? What enzyme is responsible?
|
Gln
Gln-PRPP Amidotransferase |
|
|
What is the key regulatory step in purine synthesis?
|
Gln-PRPP Amidotransferase
|
|
|
What enzyme will yield the product PR-NH2 (Phosphoribosylamine)?
|
Gln-PRPP Amidotransferase
|
|
|
What will activate and inhibited the Gln-PRPP Amidotransferase enzyme?
|
+ by PRPP
- by nucleotides |
|
|
Addition of CO2 to the purine ring structure is unique. Why?
|
No biotin
No ATP |
|
|
What is the fate of Asp after donating a N to the purine ring?
|
Recycled to TCA as fumerate
|
|
|
What is the first ring structure that is made in purine synthesis?
|
Inosine mono phosphate
|
|
|
How many ATP does it require to make one purine ring?
|
5 ATP
|
|
|
What is the handle that the purine ring is build upon?
|
PRPP
|
|
|
What does PRPP stand for?
|
phosphoribosyl pyrophosphate
|
|
|
How is adenosine made from IMP? What does it cost?
|
Addition of Asp
GTP |
|
|
What is the fate of the Asp added to make AMP from IMP?
|
Cleaved to form succinate
|
|
|
Where will ATP feedback to regulate synthesis?
|
Gln-PRPP Amidotransferase
|
|
|
How is GMP formed from IMP? What does it cost?
|
N donated by Gln (XMP intermediate)
NADH, ATP |
|
|
Where does GTP feedback to regulated nucleotide synthesis?
|
Gln-PRPP amidotransferase
At IMP to GMP branch point |
|
|
What is the first step to pyrimidine formation?
|
Formation of carbamoyl phosphate by CPS II
|
|
|
What are the regulation characteristics of CPS II?
|
+ ATP
+ PRPP - UMP (first product) |
|
|
Describe the reaction catalyzed by CPS II.
|
Substrates are Gln (leaves are Glu) and CO2
Costs 2 ATP Product is carbamoyl phosphate |
|
|
What enzyme catalyzes the addition of Asp to the pyrimidine ring?
|
Aspartate transcarbamoylase
|
|
|
What inhibits aspartate transcarbamoylase?
|
CTP (last product)
|
|
|
What is the first ring structure made during pyrimidine synthesis?
|
Orotic acid
|
|
|
When is the PRPP added to the pyrimidine?
|
Added to orotic acid to form OMP
|
|
|
How is OMP turned into UMP?
|
Decarboxylation
|
|
|
What substrate is made into the first cytosine ring?
|
UTP
|
|
|
How is UTP made into CTP?
|
Transamination with Gln
|
|
|
What are the differences between purine and pyrimidine synthesis?
|
1. Pyrimidine synthesis is linear
2. PRPP is added at the end to the pyrimidine rings |
|
|
What is the immediate need for ATP, GTP, UTP, and CTP?
|
RNA synthesis
|
|
|
What is the addition that needs to be made to make thymine from uracil?
|
Methylation
|
|
|
What is the key step needed to make thymine?
|
Need deoxyribose before methylation of uracil.
|
|
|
What enzyme is responsible for making deoxyribonucleotides?
|
Ribonucleotide Reductase
|
|
|
What kind substrate does ribonucleotide reductase use?
|
Diphospho-nucleotides
|
|
|
What protein complex will reduce ribonucleotide reductase after it has been oxidized?
|
Thioredoxin
|
|
|
What resets Thioredoxin?
|
Thioredoxin reductase
|
|
|
What forms of reducing power is need to fuel ribonucleotide reductatse?
|
Thioredoxin
FADH2 NADPH |
|
|
Describe how a dUDP is made into a dTMP.
|
dUDP is made into dUTP, then hydrolyzed to dUMP, then methylated.
|
|
|
What are the two ways to make dUMP?
|
From dUTP
From dCDP |
|
|
What carbon donor is used to make Thymine?
|
THF
|
|
|
What happens to THF after it donates a methyl to form thymine?
|
Oxidized to form Dihydroxyfolate
|
|
|
What does methotrexate do?
|
inhibits the reduction of DHF to THF
|
|
|
What kind of reducing power is used to change DHF to THF?
|
NADPH
|
|
|
What regulates the on/off of the ribonucleotide reductase?
|
high [ATP] turns it on
low [ATP] turns it off |
|
|
What is the first feedback regulator of ribonucleotide reductase? What does it do?
|
dTTP
- dCDP and dUDP binding + dGDP binding |
|
|
What is the role of dGTP for regulation of ribonucleotide reductase?
|
- dGDP binding
+ dADP binding |
|
|
What is the regulatory function of dATP on ribonucleotide reductase?
|
Shuts down the whole protein.
|
|
|
What does the phosphorylase do during the degradation of nucleotides?
|
releases Ribose-1-P
|
|
|
What form are most nucleotides salvaged?
|
As free nucleotides
|
|
|
What pyrimidine is not recycled?
|
thymine
|
|
|
Why can pyrimidines be recycled?
|
PRPP can be added to the formed ring.
|
|
|
What two enzymes allow purines to be recycled?
|
Adenine phophoribosyl transferase
Guanine/Hypoxanthine Phosphoribosyl transferase |
|
|
How is uracil degraded?
|
Cleaved to form carbamoyl beta alanine and finally to acetyl-coa
|
|
|
What are the two key intermediates of thymine degradation?
|
B-amino isobutyric acid
methyl malonyl-CoA |
|
|
What product is formed from thymine degradation?
|
succinyl-CoA
|
|
|
What is the degradation fate of adenine and guanine?
|
Excreted as Uric acid
|
|
|
What degrades guanine to xanthine?
|
Guanase
|
|
|
What form of uric acid is dominant?
|
The enol or Urate forms. Uric acid form will be dominant at low pH.
|
|
|
What is the key enzyme in adenosine degradation? What is its product?
|
Adenosine Deaminase
Inosine |
