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Biochemistry > Nucleotide Metabolism > Flashcards

Nucleotide Metabolism Flashcards

1
Q

What are nucleotides made out of?

(3)

A
  1. Nitrogenous base
  2. Pentose monosaccharide
  3. 1-3 phosphate groups
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2
Q

What are the 2 Purines?

A

Adenine and Guanine

For both DNA/RNA

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3
Q

What are the 3 pyrimidines?

A

Thymine, Cytosine, Uracil

Uracil-RNA
Thymine-DNA

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4
Q

What are the 2 common bases involved in purine metabolism?

A
  1. Hypoxanthine formation of Inosine monophosphate (IMP)
  2. Xanthine found in xanthosine MP
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5
Q

What is a nucleoside?

A

Addition of pentose sugar to a base

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6
Q

Addition of ribose sugar to bases A, G, C, T and U produce what?

A

Adenosine
Guanosine
Cytidine
Thymidine
Uridine

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7
Q

Addition of 1-3 phosphate group to a nucleoside yields what structure?

A

Nucleotide (mono, di, tri)

Phosphate groups are responsible for the negative charges w/ RNA/DNA

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8
Q

What is used to synthesize PRPP?

5-Phosphoribosyl-1-pyrophosphate

A

Ribose 5-phosphate from the HMP (non-oxidative)

Used for both purine/pyrimidine pathways

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9
Q

Is PRPP an activated or deactivated pentose?

A

Activated

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10
Q

PRPP synthetase is an X-linked enzyme. T/F?

Activation/Inhibition?

A

TRUE-from mother
* Activated by inorganic phsophate
* Inhibited by purine ribonucleotides

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11
Q

Where does De Novo Purine synthesis occur?

A

CYTOPLASM

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12
Q

What are the five precursors involved in purine de novo synthesis?

A
  1. CO2
  2. Aspartate
  3. Glycine
  4. Glutamine
  5. Folic Acid (Formyl tetrahydrofolate)
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13
Q

What is the RLS in De novo Purine Synthesis?

A

Construction of the purine ring

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14
Q

Do humans synthesize folic acid?

A

NO-thats why sulfa drugs do not interfere with humans and only the bacteria.

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15
Q

De Novo Purine Synthesis Pathway

Simplified

A
  1. PRPP
  2. IMP
  3. AMP/GMP
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16
Q

Conversion of Nucleoside Monophosphates to di and triphosphates

A

INSERT PIC

17
Q

Purine Salvage 2 enzymes involved

A
  1. HGPRT (Hypoxanthine-guanine phosphoribosyltransferase)
  2. APRT(Adenine phosphoribosyltransferase)
18
Q

Lesch-Nyhan Syndrome

A
  • X-linked recessive disorder
  • Due to deficiency of HGPRT
  • Results in an increased breakdown of purines causing elevated levels of uric acid
19
Q

Are purine rings easily cleaved in humans?

A

NO-not cleaved at all. Purine nucleotides are degraded primarily in the **liver **and the free bases are sent out and salvaged by peripheral tissues

20
Q

What is the cause of Gout?

A

Purine undersecretion OR overproduction

Immunodeficiencies include:
1. Adenosine deaminase deficiency
2. Purine nucleoside phosphorylase deficiency

21
Q

In Pyrimidine Synthesis are rings formed before or after the attachment to the ribose-5-phosphate of PRPP?

A

Before and put on in 1 piece

22
Q

What is the RLS in pyrimidine synthesis?

A

2 ATP + CO2 + Glutamine–> Carbamoyl phosphate

Enzyme is Carbamoyl Phosphate Synthetase II (CPS II)

23
Q

Are folic acid derivatives used in Pyrimidine synthesis?

A

NO
1. Aspartic acid
2. Amide of glutamine
3. CO2

24
Q

Are Pyrmidine bases highly soluble?

A

Yes-less clinically significant than purine salvage

25
Q

What is the common disorder of Pyrmidine Metabolism?

A

Orotic Aciduria
1. Poor growth
2. Megaloblastic anemia

26
Q

The reduction of ADP, CDP, UDP to dADP, dCDP, dUDP is catalyzed by what enzyme?

A

Ribonucleotide diphosphate reductase

Inhibitors: dATP, hydroxyurea

27
Q

Where does the digestion of dietary Nucleic Acids take place?

A

Occurs in the small intestine
* End product is Uric Acid

28
Q

What does Sulfonamides do?

A

Competitive inhibitors of the enzyme dihydropteroate synthetase that only efects bacteria

29
Q

What is an anti metabolite?

A

Similar to normal body molecules (slightly different structure)
* Stop cancer cells from making and repairing DNA that they need to grow and multiply

Biochemistry (15 decks)

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