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OS 201 > Nucleotide Metabolism > Flashcards

Nucleotide Metabolism Flashcards

1
Q

What are the components of nucleotides?

Hint: 3

A
  1. Bases
  2. Sugar`
  3. Phosphate`
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2
Q

Base + Sugar =

A

Nucleoside

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3
Q

Base + Sugar + Phosphate =

A

Nucleotide

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4
Q

TRUE or FALSE

Thymidine is found only in deoxyribose

A

True

You don’t say ‘deoxythimidine’ because thymidine is found only in deoxyribose

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5
Q

TRUE or FALSE

Uracil is found in RNA only

A

True

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6
Q

Where is phosphate attached in ‘deoxyribose’?

A

C3

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7
Q

Where is phosphate attached in ‘ribose’?

A

C2, C3

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8
Q

Source of nucleotides
From simple precursors
Start from starch

A

‘De novo synthesis’

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9
Q

Source of nucleotides

Use of preformed nucleosides and bases

A

Salvage reactions

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10
Q

End product in the metabolism of purine bases

A

Uric acid

Purine bodies are catabolyzed mainly to uric acid

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11
Q

Branched reaction in the biosynthesis of purine ring involves the conversion of __ to __ to ___

A

IMP —> GMP —> AMP

GMP - donor of amino group is glutamine
Conversion of IMP to GMP is an oxidation reaction

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12
Q

The synthesis of GMP from IMP needs an energy source. Why is this so?

a. For regulation
b. To maintain equimolar concentrations of both types of nucleotides - AMP and GMP
c. GMP is needed to biosynthesize AMP
d. All of the above

A

D

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13
Q

The ‘committed step’ in the biosynthesis of purine bases involves?

A

Glutamine amidotransferase

Kapag nagsimula ito, tuloy-tuloy na

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14
Q

What are the points of regulation in the synthesis of purine bases?

A
  1. PRPP Synthetase

2. Glutamine amidotransferase

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15
Q

Which biosynthesis is simpler? And why?

A

Biosynthesis of Pyrimidine Bases

Simple = straight pathway

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16
Q

What is used in the biosynthesis of pyrimidine bases, CPS I or CPS II?

CPS = Carbamoyl Phosphate

A

CPS II

  • PYRIMIDINE BIOSYNTHESIS
  • Found everywhere
  • Cytosol
  • Amide group of glutamine

CPS I

  • UREA CYCLE
  • Liver
  • Mitochondrion
  • Ammonium ion
17
Q

What is the end product of pyrimidine? It is the first pyrimidine nucleotide?

A

UMP

18
Q

What is the point of regulation in the synthesis of pyrimidine in animals?

A

UMP

19
Q

Why is regulation of purine and pyrimidine needed?

A

There should be control, when certain metabolism are in excess

Both processes are energy requiring. Pathways should be regulated so there would be no waste

20
Q

This enzyme in pyirimidine synthesis is a regulator of PRPP and is needed for the synthesis of purine

A

TDP

21
Q

This reaction use preformed reaction of purine and nucleosides

Occur in most cells (non-hepatic)

A

Salvage reaction

22
Q

What is this syndrome?

  • uric acid in the blood
  • tendency to do self-mutilation
A

Lesch-Nyhan Syndrome

23
Q

How are deoxyribonucleotides formed?

A

Ribonucleotide reductase

24
Q

4 ribonucleoside phosphates

A

ADP
GDP
CDP
UDP

25
Q

There is a need to maintain ratio of ribonucleotides ro deoxyribonucleotides. What is the BEST regulator?

A

dATP (deoxyATP)

26
Q

Found only in DNA

Precursor of thymidine

A

Thymidylate

27
Q

Difference between UMP and TMP

A

Methyl group attached at C5

28
Q

Inhibitor of thymidylate synthetase

A 
5 fluorouracil (anticancer drug)
Side effects: Falling hair (where cells easily divide)

TMP is needed for biosynthesis of nucleic acids (cell division)

29
Q

End product of the degradation of purine nucleotides

A

Uric acid

30
Q

TRUE or FALSE

Degradation of pathway involves oxidation reaction but the ring system remains intact

A

True

31
Q

Immune deficiency due to defective adenosine

Involves T-cell and B-cell dysfunction

A

SCID

32
Q

Characterized by hyperuricemia resulting in painful swelling of joints
Deposition of urate crystals

Primary causes are primary enzymes

  • defective PRPP synthetase:
  • lack of xanthine oxidase:
A

Gout

Hyperuricemia
Hypouricemia

33
Q

Suicide inhibitor used to treat gout
Structure is similar to hypoxanthine
Once it is bound, the normal substrate can no longer bind to the enzyme

A

Allopurinol

34
Q

End products in the degradation of pyrimidine nucleotides and their clinical importance

A

Beta-alanine
Beta-aminoisobutyrate

Clinical correlation: SOLUBLE
So, it is not a major concern unlike gout which involves deposition of crystals

35
Q

Difference between amount of nitrogen intake and outtake

A

Nitrogen balance

36
Q

TRUE or FALSE

Hydroxyl group (-OH) at C-2 in ribose is replaced by hydrogen (-H) in deoxyribose

A

True

37
Q

Explain the digestion of dietary nucleic acids (6 STEPS)

A
  1. Nucleic acids ingested in the form of nucleoproteins (denatured by acidity, lose H-bonds but retain phosphodiester bonds)
  2. Denatured nucleic acids are subjected to nucleases, which produces oligonucleotides (shorter chains)
  3. Cleaved by phosphodiesterases, which cleave phosphodiester bonds one at a time
  4. Nucleases and phosphodiesterase cleave oligonucleotides into mononucleotides
  5. Nucleotides dephosphorylate mononucleotides into nucleosides
  6. Nucleosidases spit the nucleotides further into sugar and base
38
Q

TRUE or FALSE

Hydroxyl group (-OH) at C-2 in ribose is replaced by hydrogen (-H) in deoxyribose

A

True

39
Q

Explain the digestion of dietary nucleic acids (6 STEPS)

A
  1. Nucleic acids ingested in the form of nucleoproteins (denatured by acidity, lose H-bonds but retain phosphodiester bonds)
  2. Denatured nucleic acids are subjected to nucleases, which produces oligonucleotides (shorter chains)
  3. Cleaved by phosphodiesterases, which cleave phosphodiester bonds one at a time
  4. Nucleases and phosphodiesterase cleave oligonucleotides into mononucleotides
  5. Nucleotides dephosphorylate mononucleotides into nucleosides
  6. Nucleosidases spit the nucleotides further into sugar and base

OS 201 (9 decks)

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