Nucleic Acid Metabolism Flashcards

1
Q

What are the two pathways to make necleotides?

A

De novo and salvage pathways

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2
Q

What is the beginning of nucleotides in de novo synthesis pathways?

A

Synthesis of ribonucleotides

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3
Q

Why would blocking de novo have little effect?

A

If cell has source of bases or nucleotides, salvage pathway can be used

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4
Q

Why would blocking the salvage pathway have little effect?

A

Cells could synthesize nucleotides by the de novo pathway

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5
Q

Where does de novo synthesis occur?

A

Cytosol

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6
Q

Where is the purine ring synthesized in de novo?

A

1’ carbon of ribose 5-phosphate

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7
Q

What is the first nucleotide formed in de novo purine synthesis?

A

Inosine monophosphate (IMP)

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8
Q

What are the steps of IMP synthesis?

A
  1. Activation of ribose-5-phosphate?
  2. Acquisition of purine atom N9
  3. Purine ring completion by successive activation of carbon-bound oxygen by phosphorylation
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9
Q

What stimulates or inhibits AMP synthesis?

A

Low GTP INHIBITS
Hight GTP STIMULATES

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10
Q

How is de novo purine synthesis inhibited?

A

High IMP, AMP, GMP

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11
Q

How is de novo purine synthesis stimulated?

A

High PRPP

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12
Q

True or false. De Novo synthesis of pyrimidine nucleotides is non-linear.

A

False; it is linear.

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13
Q

What are the steps of de novo synthesis of pyrimidine nucleotides?

A
  1. Synthesis of UMP
  2. Synthesis of carbamoyl aspartate
  3. Ring closure to form dihydroorotate
  4. Oxidation of dihydroorotate
  5. Acquisition of ribose phosphate
  6. Decarboxylation of OMP to form UMP
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14
Q

What do nucleotide kinases do?

A

Convert monophosphates to di- and tri-phosphates

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15
Q

What are the three types of salvage enzymes?

A

Nucleoside kinases
Nucleoside phosphorylases
Phosphoribosyl transferases

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16
Q

What are the ways that nucleotides are catabolized?

A

Nucleic acid catabolism
Nucleotide catabolism
Further catabolism of purine and pyrimidine bases

17
Q

What must happen for TMP synthesis to continue?

A

THF oxidized to DHF and reduced back to THF