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BMSC 230 > Chapter 32 - Metabolism of Nucleotides > Flashcards

Chapter 32 - Metabolism of Nucleotides Flashcards

1
Q

Which have more DNA and RNA: meats of fruits and veggies?

A

meat

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2
Q

While only __% of nucleosides absorbed are reutilized for nucleic acid synthesis, __% of these are used by rapidly regenerating enterocytes.

A

5, 25

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3
Q

nucleoside vs nucleotide

A

nucleotide contains 1 or more phosphate

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4
Q

deoxy-

A

one less oxygen

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5
Q

functions of nucleotides

A
  • precursors of DNA and RNA
  • ATP is an energy currency in biological systems
  • adenine nucleotides are components of 3 major coenzymes (NAD, FAD, CoA
  • activated intermediates in many biosynthetic pathways
  • metabolic and physiological regulators
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6
Q

biosynthesis of purine nucleotides (A, G)

A

very little obtained from diet is used and most converted to uric acid which is secreted
-two pathways (de novo, salvage)

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7
Q

de novo pathway of purine nucleotides

A

precursors: Ribose 5-P, Aspartate, CO2, Gly, Gln, formate

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8
Q

5-Phosphoribosyl 1-pyrophosphate

A

PRPP; activated form of ribose 5-P

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9
Q

first committed step and point of regulation in de novo synthesis of purines is catalyzed by…

A

glutamine-PRPP amidotransferase

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10
Q

When making AMP, ____ is used

A

GTP

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11
Q

When making GMP, ____ is used.

A

ATP

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12
Q

AMP is formed by..

A

by the addition of aspartate followed by the release of fumarate.

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13
Q

GMP is formed by…

A

addition of water, dehydrogenation by NAD+, and the replacement of the carbonyl oxygen atom by
—NH2 derived by the hydrolysis of glutamine

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14
Q

During Purine nucleotide biosynthesis, what inhibits PRPP synthetase

A

ADP

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15
Q

During Purine nucleotide biosynthesis, what inhibits Gln-PRPP amidotransferase

A

AMP, GMP, IMP

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16
Q

During Purine nucleotide biosynthesis, what inhibits adenylosuccinate synthetase

A

AMP

17
Q

During Purine nucleotide biosynthesis, what inhibits IMP dehydrogenase

A

GMP

18
Q

Adenine phosphoribosyltransferase (APRT) catalyzes the formation of…

A

adenylate (AMP)

19
Q

hypoxanthine-guanine phosphoribosyltransferase (HGPRT) catalyzes the formation of …

A

guanylate (GMP) as well as inosinate (IMP)

20
Q

Which is major and which is minor: APRT or HGPRT?

A

minor: APRT (because most of the adenine is converted to hypoxanthine)
major: HGPRT

21
Q

gout

A

characterized by high blood levels of
uric acid due to overproduction or
underexcretion of uric acid

22
Q

gout treatments

A

grades, excretion stimulants, dietary and alcohol restrictions

23
Q

Lesch Nyhan Syndrome

A
  • deficiency in HGPRT activity due to mutations in the gene

- X linked and mostly affects males

24
Q

Lesch Nyhan Syndrome consequence

A

The combination of increased synthesis, and decreased utilization, of purines leads to high levels of uric acid production

25
Q

de novo pathway of pyrimidine nucleotides (U, C)

A

precursors: R5-P, CO2, Gln, Aspartate
- synthesize carbamoyl phosphate
- build pyrimidine ring (orotate)
- link orotate to R5P

26
Q

synthesis of carbamoyl phosphate

A
  • rate limiting step in pyrimidine synthesis

- carbamoyl phosphate synthetase II (CPSII)

27
Q

CPS I vs CPS II: metabolic process

A
  • urea synthesis

- pyrimidine nucleotide synthesis

28
Q

CPS I vs CPS II: location

A
  • mitochondrial matrix

- cytosol

29
Q

CPS I vs CPS II: N donor

A
  • NH4+

- Gln

30
Q

CPS I vs CPS II: regulatory effectors

A

I: (+) N-acetylGlu, (+) Arginine
II: (-) UTP, (+) ATP, PRPP

31
Q

5-phosphoribosyl-1-pyrophosphate

A

active form of ribose5P

-addition of pyrophosphate from ATP in a rxn catalyzed by PRPP synthetase

32
Q

ribonucleotide reductase

A

reduction of ribonucleotides to deoxyribonucleotides

33
Q

ultimate reductant

A

NADPH

34
Q

chemotherapeutic agents

A

Inhibition of biosynthesis of DNA is a basis for some chemotherapies to slow up cell division (inhibition of thymidylate synthase and dihydrofolate reducatase)

35
Q

inhibitors of thymidylate synthase

A

5-fluorouracil, Raltitrexed

36
Q

inhibitors of dihydrofolate reductase

A

methotrexate (slows diwn psoriasis)

BMSC 230 (15 decks)

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