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Metabolism > 2.13 Purines and Pyrimidines > Flashcards

2.13 Purines and Pyrimidines Flashcards

0
Q

what kind of a linkage exists between nucleotides

A

Phosphodiester linkage

3’ to 5’

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1
Q

Difference between ribonucleotides and deoxyribonucleotides

A

2’ position has an OH group on Ribonucleotides

2’ position has an H group on Deoxyribonucleotides

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2
Q

What are the precursor molecules to Purine Synthesis

A 
Glycine
Aspartic Acid
Glutamine
CO2
Tetrahydrofolate coenzymes
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3
Q

Precursors for Pyrimidine Synthesis

A

Aspartic acid
Glutamine
CO2

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4
Q

What is the general precursor for synthesis of NT

A

Amino Acid
Ribose 5 phosphate
CO2
NH3

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5
Q

T or F, Pyrimidines have two rings, 1- 5 membered ring and 1- 6 membered ring

A

False, This is true for PUrines

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6
Q

Where does purine synthesis occur?

A

Liver and partly in peripheral tissues

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7
Q

What reaction occurs to form the activated PRPP

A

Ribose 5 Phosphate + ATP = PRPP

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8
Q

What enzyme catalyzes the reaction to activate PRPP

A

PRPP Synthetase

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9
Q

How is PRPP used differently in Purine and Pyrimidine synthesis?

A

Purine: Sugar is assembled from PRPP and added to a base
Pyrimidine: Base is assembled and then added to PRPP (sugar)

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10
Q

What are the “parent” molecule in both purine and pyrimidine biosynthesis

A

Purine: IMP
Pyrimidine: OMP

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11
Q

What is the rate limiting step in Purine Synthesis

A

PRPP–> 5 phosphoribosyl 1-amine

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12
Q

What enzyme catalyzed the rate-limiting step in Purine synthesis

A

PRPP amidotransferase

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13
Q

What is the rate limiting step in Pyrimidine synthesis

A

Precursors –> Carbamoyl Phosphate

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14
Q

What enzyme catalyzes the rate-limiting step in Pyrimidine synthesis

A

Carbamoyl Phosphate Synthetase II

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15
Q

What inhibits CPS II in pyrimidine synthesis ?

A

UTP

16
Q

Where does the rate limiting step of Pyrimidine synthesis occur?

A

Cytosol (Note: CPS 1 occurs in mitochondria)

17
Q

What enzyme catalyzes conversion of Ribonucleotides to Deoxyribonucleotides?

A

Ribonucleotide Reductase

18
Q

What must be oxidized for the conversion of Ribonucleotides to Deoxyribonucleotides?

A

Thioredoxin

19
Q

What are the two enzymes involved in Purine base salvage

A

Adenine Phosphoribosyl Transferase

Hypoxanthine-Guanine Phosphoribosyl transferase

20
Q

What may occur because of a deficiency to HGPRT?

A

20% of gout occurs due to this enzyme deficiency

21
Q

In case of AMP, what amino acid provides the NH group?

A

Aspartate

22
Q

In the case of GMP, what amino acid provides the NH group

A

Glutamine

23
Q

What causes Gout?

A

Hyperuricemia

24
Q

What is the deficiency that leads to Lesch-Nyhan disease?

A

HGPRT deficiency

It is inherited

Metabolism (31 decks)

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