Purine, Pyrimidine, and Nucleotide Metabolism - Parts 1 & 2 Flashcards Preview

Digestive, Endocrine, and Metabolic Systems > Purine, Pyrimidine, and Nucleotide Metabolism - Parts 1 & 2 > Flashcards

Flashcards in Purine, Pyrimidine, and Nucleotide Metabolism - Parts 1 & 2 Deck (27):
1

___________ have two rings.

Purines (Two-rines)

2

Compare and contrast the starting points for the synthesis of purines and pyrimidines.

Purines: starts with ribose

Pyrimidines: starts with base and adds sugar at the end

3

The form of __________ in the mitochondria takes part in the urea cycle, while the cytosolic form participates in pyrimidine synthesis.

carbamoyl phosphate synthase

4

In purine synthesis, ___________ is converted to AMP and GMP.

IMP

5

__________ is converted to CTP.

UTP

6

What is the first step in purine synthesis?

Ribose 5-phosphate
(PRPP synthetase) ***Regulated step***
5-phosphoribosyl-1-pyrophosphate

7

After PRPP synthetase, what is the next regulated step in the synthesis of IMP?

5-PRPP
(Glutamine phosphoribosyl pyrophosphate amidotransferase) ***Inhibited by GMP, AMP, and IMP; activated by PRPP***
5-phosphoribosylamine

8

These two enzymes are both allosterically inhibited by IMP, GMP, and AMP: _______________.

PRPP synthetase and glutamine PRPP amidotransferase

9

The key regulated enzyme in pyrimidine synthesis is _________________.

2x ATP + CO2 + glutamate
(Carbamoyl phosphate synthetase II [in the cytosol])
Carbamoyl phosphate

10

Ribonucleosides are converted to deoxyribonucleosides by the enzyme _________________.

ribonucleotide reductase

11

ATP _____________ ribonucleotide reductase, while dATP _____________ it.

activates; deactivates

12

Allopurinol inhibits ______________.

xanthine oxidase

13

What enzyme converts adenosine to inosine?

Adenosine deaminase

14

The two key enzymes in purine degradation are ________________.

(1) adenosine deaminase and (2) xanthine oxidase

15

Those with Lesch-Nyhan cannot convert ________ to __________ or __________ to __________.

guanine; GMP

hypoxanthine; IMP

16

Nucleoside is ______________, while nucleotide is _______________.

base and sugar; base, sugar, and phosphate

17

In general, the body relies on ______________ when it needs nucleotides.

the salvage pathway

18

True or false: methotrexate inhibits the production of pyrimidines.

False. Purines.

19

What is created first in the pyrimidine synthesis pathway?

UMP; it must be converted to UTP before being converted to CTP

20

The enzyme ribonucleotide reductase is inhibited by ____________.

dNTP

21

Ribonucleotide reductase does not recognize _______.

TMP, so to get dTMP you need to make dUDP first

22

Describe the overall process of purine breakdown.

First, the base is separated from the sugar, then the base is broken down to uric acid and excreted in the urine.

23

After pyrimidines are separated from their sugars, what happens?

The ring is broken open.

24

PRPP synthase is activated by high amounts of ______________.

inorganic phospate

25

5-flurouracil inhibits the synthesis of _____________.

dTMP (because 5FU enters the enzyme thymidylate synthase and inhibits it)

26

Without adenosine deaminase, dATP builds up in the blood. Why is this a problem?

Because dATP is a potent inhibitor of DNA synthesis

27

Degradation of _____________ can lead to increased production of substrates for the TCA cycle.

pyrimidines

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