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Jaspie - Biochemistry II > VII - Nucleotides > Flashcards

VII - Nucleotides Flashcards

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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
De Novo Purine Synthesis: Rate-Limiting Enzyme
Glutamyl PRPP Amidotransferase
26
Glutamyl PRPP Amidotransferase: Inhibitors
5'-nucleotides, AMP, GMP, IMP
27
Product from hypoxanthine, parent purine nucleotide
Inosine Monophosphate (IMP)
28
De Novo Purine Synthesis: Requires a two-step energy-requiring pathway
Conversion of IMP to AMP/GMP
29
AMP synthesis requires
GTP
30
GMP synthesis requires
ATP
31
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
Purine Salvage
32
Purine Salvage: Irrevesible Enzymes
Adenine Phosphoribosyltransferase (APRT), Hypoxanthine-Guanine Phosphoribosyltransferase (HGPRT)
33
Carbamoyl Phosphate Synthetase: mitochondria
CPS I
34
Carbamoyl Phosphate Synthetase: Urea Cycle
CPS I
35
Carbamoyl Phosphate Synthetase: nitrogen from ammonia
CPS I
36
Carbamoyl Phosphate Synthetase: activated by N-acetylglutamate
CPS I
37
Carbamoyl Phosphate Synthetase: cytosol
CPS II
38
Carbamoyl Phosphate Synthetase: Pyrimidine Synthesis
CPS II
39
Carbamoyl Phosphate Synthetase: nitrogen from γ-amide group of glutamine
CPS II
40
Carbamoyl Phosphate Synthetase: inhibited by UTP, activated by ATP
CPS II
41
Steps in De Novo Pyrimidine Synthesis
Synthesis of Carbamoyl Phosphate, Orotic Acid, Pyrimidine Nucleotide, UTP & CTP, dTMP from dUMP
42
De Novo Pyrimidine Synthesis: Rate-Limiting Step
Synthesis of Carbamoyl Phosphate
43
De Novo Pyrimidine Synthesis: Rate-Limiting Enzyme
Carbamoyl Phosphate Synthetase II
44
Carbamoyl Phosphate Synthetase II: Inhibitor
UTP
45
Carbamoyl Phosphate Synthetase II: Activators
ATP, PRPP
46
The only enzyme for synthesis of orotic acid inside the mitochondria
Dihydroorotate Dehydrogenase
47
Parent pyrimidine nucleotide
Orotidine Monophosphate (OMP)
48
OMP is converted to Uridine Monophosphate (UMP) by
OMP Decarboxylase
49
Synthesizes UTP and CTP
CTP Synthetase
50
Synthesizes dTMP from dUMP using N5,N10-methenyltetrahydrofolate as the source of the methyl group
Thymidylate Synthase
51
Salvageable Pyrimidines
Uridine, Cytidine (uridine-cytidine kinase), Deoxycytidine (deoxycitidine kinase), Thymidine (thymidine kinase)
52
Nucleoside diphosphates are synthesized from the corresponding nucleoside monphosphates using
Base-Specific Nucleoside Monophosphate Kinases
53
Source of the transferred phosphate in the synthesis of diphosphates and triphosphates
ATP
54
Deoxyribonucleotide Synthesis: Enzyme
Ribonucleotide Reductase
55
Multisubunit enzyme specific for the reduction of nucleoside diphosphates to their deoxy forms
Ribonucleotide Reductase
56
Regenerates the reduced form of ribonucleotide reductase
Thioredoxin
57
Reconverts thioredoxin to its reduced form
NADPH
58
Degradation of dietary nucleic acids occurs in
small intestines
59
Hydrolyze nucleotides to nucleosides and free bases
pancreatic enzymes
60
Dietary purines are generally converted to
uric acid
61
The _____ ring can be opened and degraded to highly soluble structures.
pyrimidine
62
Pyrimidine Degradation: roducts
β-alanine (precursor for acetyl CoA), β-aminoisobutyrate (precursor for succinyl-CoA)
63
Structural analogs of PABA that competitively inhibit bacterial synthesis of folic acid
Sulfonamides
64
Co-enzyme for purine synthesis
Tetrahydrofolate (THF)
65
Inhibit the reduction of dihydrofolate to tetrahydrofolate catalyzed by dihydrofolate reductase
Methotrexate, Trimethoprim
66
hyperuricemia with recurrent attacks of acute arthritis caused by deposition of uric acid crystals
Gouty Arthritis
67
Gouty Arthritis: no known cause
Primary
68
Gouty Arthritis: ↑ cell turnover, ↑ UA production, ↓ UA excretion
Secondary
69
Gouty Arthritis: Acute Phase Management
NSAIDs, steroids, colchicine
70
Gouty Arthritis: Intercritical Phase Management
allopurinol (overproducers), probenecid (underexcretors)
71
X-linked recessive deficiency in HGPRT that causes a rise in intracelular PRPP, hyperuricemia, mental retardation, self-mutilation
Lesch-Nyhan Syndrome
72
Purine overproduction and hyperuricemia secondary to enhanced generation of PRPP precursor of 5-phosphate
Von Gierke's Disease
73
Leads to severe combined immunodeficiency (T and B lymphocytes), high dATP which inhibits ribonucleotide reductase and inhibits formation of deoxyribonucleotides
Adenosine Deaminase Deficiency (SCID)
74
Metabolically converted to 5-FdUMP which becomes permanently bound to the inactivated thymidylate synthase
5 Fluorouracil
75
Low activities of orotidine phosphate decarboxylase and orotate phosphoribosyltransferase, abnormal growth, megaloblastic anemia, excretion of large amounts of orotate in the urine
Orotic Aciduria
76
Orotic Aciduria: Treatment
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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