2.13 Purines and Pyrimidines Flashcards Preview

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Flashcards in 2.13 Purines and Pyrimidines Deck (25):
0

Difference between ribonucleotides and deoxyribonucleotides

2' position has an OH group on Ribonucleotides
2' position has an H group on Deoxyribonucleotides

1

what kind of a linkage exists between nucleotides

Phosphodiester linkage
3' to 5'

2

What are the precursor molecules to Purine Synthesis

Glycine
Aspartic Acid
Glutamine
CO2
Tetrahydrofolate coenzymes

3

Precursors for Pyrimidine Synthesis

Aspartic acid
Glutamine
CO2

4

What is the general precursor for synthesis of NT

Amino Acid
Ribose 5 phosphate
CO2
NH3

5

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

False, This is true for PUrines

6

Where does purine synthesis occur?

Liver and partly in peripheral tissues

7

What reaction occurs to form the activated PRPP

Ribose 5 Phosphate + ATP = PRPP

8

What enzyme catalyzes the reaction to activate PRPP

PRPP Synthetase

9

How is PRPP used differently in Purine and Pyrimidine synthesis?

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

10

What are the "parent" molecule in both purine and pyrimidine biosynthesis

Purine: IMP
Pyrimidine: OMP

11

What is the rate limiting step in Purine Synthesis

PRPP--> 5 phosphoribosyl 1-amine

12

What enzyme catalyzed the rate-limiting step in Purine synthesis

PRPP amidotransferase

13

What is the rate limiting step in Pyrimidine synthesis

Precursors --> Carbamoyl Phosphate

14

What enzyme catalyzes the rate-limiting step in Pyrimidine synthesis

Carbamoyl Phosphate Synthetase II

15

What inhibits CPS II in pyrimidine synthesis ?

UTP

16

Where does the rate limiting step of Pyrimidine synthesis occur?

Cytosol (Note: CPS 1 occurs in mitochondria)

17

What enzyme catalyzes conversion of Ribonucleotides to Deoxyribonucleotides?

Ribonucleotide Reductase

18

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

Thioredoxin

19

What are the two enzymes involved in Purine base salvage

Adenine Phosphoribosyl Transferase
Hypoxanthine-Guanine Phosphoribosyl transferase

20

What may occur because of a deficiency to HGPRT?

20% of gout occurs due to this enzyme deficiency

21

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

Aspartate

22

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

Glutamine

23

What causes Gout?

Hyperuricemia

24

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

HGPRT deficiency
It is inherited