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Jaspie - Biochemistry II > VII - Nucleotides > Flashcards

VII - Nucleotides Flashcards

1
Q

Monomer units or buiding blocks of nucleic acids

A

nucleotides

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2
Q

Form part of many co-enzymes, serve as donors of phosphoryl groups, second messengers, allosteric regulators, synthetic analogs

A

nucleotides

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3
Q

Nitrogen-containing heterocycles, cyclic compounds whose rings contain both carbon and other elements, their planar characteristics facilitates stacking

A

purines & pyrimidines

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4
Q

Pyrimidines

A

Cytosine, Uracil, Thymine

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5
Q

Purines

A

Adenine, Guanine

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6
Q

Sugar + Purine/Pyrimidine

A

nucleoside

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7
Q

Link between sugar & purine/pyrimidine

A

β-N-Glucosidic Bond

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8
Q

Nucleoside with a phosphoryl group esterified to a hydroxyl group of a sugar

A

nucleotide

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9
Q

Most common form of nucleotides, phosphoryl group attached to the C-5 of pentose

A

5’-nucleotides

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10
Q

5’-phosphoryl group forms a phosphodiester bond with the 3’-OH of another nucleotide, phoshodiesterases catalyze the hydrolysis of phosphodiester bonds, slow spontaneous hydrolysis

A

polynucleotide

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11
Q

DNA is ___ stable than RNA.

A

more (DNA > RNA)

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12
Q

Polynucleotides are _____ macromolecules.

A

directional

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13
Q

Nucleotide Synthesis: sugar first

A

Purine Synthesis

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14
Q

The purine ring is constructed by adding carbons and nitrogens to a

A

preformed ribose 5-phosphate

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15
Q

Purine Synthesis: Substrates

A

Aspartic Acid, Glutamine, Carbon Dioxide, Glycine, N10-formyltetrahydrofolate / N5,N10-methenyltetrahydrofolate

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16
Q

Nucleotide Synthesis: ring first

A

Pyrimidine Synthesis

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17
Q

Pyrimidine Synthesis: Substrates

A

Aspartic Acid, Glutamine, Carbon Dioxide

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18
Q

Steps in De Novo Purine Synthesis

A

Synthesis of 5-phosphoribosyl-1-pyrophoshate (PRPP), 5’-phosphoribosylamine, Inosine Monophosphate, Conversion of IMP to AMP/GMP

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19
Q

De Novo Purine Synthesis: activated pentose that participates in the synthesis of purines and pyrimidines and in the salvage of purine bases

A

5-phosphoribosyl-1-pyrophoshate (PRPP)

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20
Q

Synthesis of 5-phosphoribosyl-1-pyrophoshate (PRPP): Substrates

A

ATP, Ribose 5-phosphate

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21
Q

Synthesis of 5-phosphoribosyl-1-pyrophoshate (PRPP): Enzyme

A

PRPP Synthetase

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22
Q

Synthesis of 5-phosphoribosyl-1-pyrophoshate (PRPP): Activator

A

inorganic phosphate (Pi)

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23
Q

Synthesis of 5-phosphoribosyl-1-pyrophoshate (PRPP): Inhibitor

A

purine nucleotides

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24
Q

Committed step in purine nucleotide biosynthesis

A

Synthesis of 5’-phosphoribosylamine

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25
Q

De Novo Purine Synthesis: Rate-Limiting Enzyme

A

Glutamyl PRPP Amidotransferase

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26
Q

Glutamyl PRPP Amidotransferase: Inhibitors

A

5’-nucleotides, AMP, GMP, IMP

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27
Q

Product from hypoxanthine, parent purine nucleotide

A

Inosine Monophosphate (IMP)

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28
Q

De Novo Purine Synthesis: Requires a two-step energy-requiring pathway

A

Conversion of IMP to AMP/GMP

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29
Q

AMP synthesis requires

A

GTP

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30
Q

GMP synthesis requires

A

ATP

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31
Q

Purines that result from the normal turnover of cellular nucleic acids or that are obtained from the diet and not degraded, can be reconverted into nucleoside triphosphates and used by the body

A

Purine Salvage

32
Q

Purine Salvage: Irrevesible Enzymes

A

Adenine Phosphoribosyltransferase (APRT), Hypoxanthine-Guanine Phosphoribosyltransferase (HGPRT)

33
Q

Carbamoyl Phosphate Synthetase: mitochondria

A

CPS I

34
Q

Carbamoyl Phosphate Synthetase: Urea Cycle

A

CPS I

35
Q

Carbamoyl Phosphate Synthetase: nitrogen from ammonia

A

CPS I

36
Q

Carbamoyl Phosphate Synthetase: activated by N-acetylglutamate

A

CPS I

37
Q

Carbamoyl Phosphate Synthetase: cytosol

A

CPS II

38
Q

Carbamoyl Phosphate Synthetase: Pyrimidine Synthesis

A

CPS II

39
Q

Carbamoyl Phosphate Synthetase: nitrogen from γ-amide group of glutamine

A

CPS II

40
Q

Carbamoyl Phosphate Synthetase: inhibited by UTP, activated by ATP

A

CPS II

41
Q

Steps in De Novo Pyrimidine Synthesis

A

Synthesis of Carbamoyl Phosphate, Orotic Acid, Pyrimidine Nucleotide, UTP & CTP, dTMP from dUMP

42
Q

De Novo Pyrimidine Synthesis: Rate-Limiting Step

A

Synthesis of Carbamoyl Phosphate

43
Q

De Novo Pyrimidine Synthesis: Rate-Limiting Enzyme

A

Carbamoyl Phosphate Synthetase II

44
Q

Carbamoyl Phosphate Synthetase II: Inhibitor

A

UTP

45
Q

Carbamoyl Phosphate Synthetase II: Activators

A

ATP, PRPP

46
Q

The only enzyme for synthesis of orotic acid inside the mitochondria

A

Dihydroorotate Dehydrogenase

47
Q

Parent pyrimidine nucleotide

A

Orotidine Monophosphate (OMP)

48
Q

OMP is converted to Uridine Monophosphate (UMP) by

A

OMP Decarboxylase

49
Q

Synthesizes UTP and CTP

A

CTP Synthetase

50
Q

Synthesizes dTMP from dUMP using N5,N10-methenyltetrahydrofolate as the source of the methyl group

A

Thymidylate Synthase

51
Q

Salvageable Pyrimidines

A

Uridine, Cytidine (uridine-cytidine kinase), Deoxycytidine (deoxycitidine kinase), Thymidine (thymidine kinase)

52
Q

Nucleoside diphosphates are synthesized from the corresponding nucleoside monphosphates using

A

Base-Specific Nucleoside Monophosphate Kinases

53
Q

Source of the transferred phosphate in the synthesis of diphosphates and triphosphates

A

ATP

54
Q

Deoxyribonucleotide Synthesis: Enzyme

A

Ribonucleotide Reductase

55
Q

Multisubunit enzyme specific for the reduction of nucleoside diphosphates to their deoxy forms

A

Ribonucleotide Reductase

56
Q

Regenerates the reduced form of ribonucleotide reductase

A

Thioredoxin

57
Q

Reconverts thioredoxin to its reduced form

A

NADPH

58
Q

Degradation of dietary nucleic acids occurs in

A

small intestines

59
Q

Hydrolyze nucleotides to nucleosides and free bases

A

pancreatic enzymes

60
Q

Dietary purines are generally converted to

A

uric acid

61
Q

The _____ ring can be opened and degraded to highly soluble structures.

A

pyrimidine

62
Q

Pyrimidine Degradation: roducts

A

β-alanine (precursor for acetyl CoA), β-aminoisobutyrate (precursor for succinyl-CoA)

63
Q

Structural analogs of PABA that competitively inhibit bacterial synthesis of folic acid

A

Sulfonamides

64
Q

Co-enzyme for purine synthesis

A

Tetrahydrofolate (THF)

65
Q

Inhibit the reduction of dihydrofolate to tetrahydrofolate catalyzed by dihydrofolate reductase

A

Methotrexate, Trimethoprim

66
Q

hyperuricemia with recurrent attacks of acute arthritis caused by deposition of uric acid crystals

A

Gouty Arthritis

67
Q

Gouty Arthritis: no known cause

A

Primary

68
Q

Gouty Arthritis: ↑ cell turnover, ↑ UA production, ↓ UA excretion

A

Secondary

69
Q

Gouty Arthritis: Acute Phase Management

A

NSAIDs, steroids, colchicine

70
Q

Gouty Arthritis: Intercritical Phase Management

A

allopurinol (overproducers), probenecid (underexcretors)

71
Q

X-linked recessive deficiency in HGPRT that causes a rise in intracelular PRPP, hyperuricemia, mental retardation, self-mutilation

A

Lesch-Nyhan Syndrome

72
Q

Purine overproduction and hyperuricemia secondary to enhanced generation of PRPP precursor of 5-phosphate

A

Von Gierke’s Disease

73
Q

Leads to severe combined immunodeficiency (T and B lymphocytes), high dATP which inhibits ribonucleotide reductase and inhibits formation of deoxyribonucleotides

A

Adenosine Deaminase Deficiency (SCID)

74
Q

Metabolically converted to 5-FdUMP which becomes permanently bound to the inactivated thymidylate synthase

A

5 Fluorouracil

75
Q

Low activities of orotidine phosphate decarboxylase and orotate phosphoribosyltransferase, abnormal growth, megaloblastic anemia, excretion of large amounts of orotate in the urine

A

Orotic Aciduria

76
Q

Orotic Aciduria: Treatment

A

diet rich in uridine results in the improvement of the anemia and decreased excretion of orotate

Jaspie - Biochemistry II (15 decks)

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