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MCBM EXAM 4 > Nucleotide Metabolism > Flashcards

Nucleotide Metabolism Flashcards

1
Q

When you synthesize common new nucleotides

A

de novo synthesis

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2
Q

What is the purine ring precursor?

A

hypoxanthine (a nitrogenous base)

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3
Q

What is the pyrimidine ring precursor?

A

Oroate (a nitrogenous base and carboxylic acid)

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4
Q

T/F: While purine precursor is

directly synthesized on ribose C-1, the pyrimidine is synthesized stepwise then attached to the ribose C-1

A

T

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5
Q

Precursors hypoxanthine and orotate are coupled with

A

5-phosphoribosyl-1-pyrophosphate (PRPP)

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6
Q

Synthesis of PRPP requires what enzyme?

A

PRPP synthetase

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7
Q

PRPP (1-pyrophosphate) activated C1 on what sugar?

A

Ribose

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8
Q

PRPP is a key substrate in both a ____ and ____ synthesis

A

purine and pyrimidine

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9
Q

Is synthesis of PRPP a committed step or not

A

no, it creates 2 different substrates

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10
Q

During ____ synthesis, a 5 membered ring is built on PRPP first

A

purine

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11
Q

Methyl groups in the formation of purine come from

A

N10-formyl-tetrahydro-folate

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12
Q

T/F: In purine synthesis, methyl groups come from SAM

A

False, they comes from N10-formyl-tetrahydro-folate

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13
Q

AMP and GMP are made from

A

IMP

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14
Q

The precursor for Adenylate (AMP) and Guanylate (GMP) is

A

Inositate IMP

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15
Q

You use ____ (ATP/GTP) when synthesizing adenylate, and ____(ATP/GTP) when synthesizing Guanylate

A

GTP, ATP

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16
Q

When making adenylate, your nitrogen donating group is ____

A

Aspartate

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17
Q

When making guanylate you use what a nitrogen donating group?

A

Glutamine (Gln)

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18
Q

During de novo pyrimidine biosynthesis, the first step is

A

formation of carbamoyl phosphate

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19
Q

Glutamine can be turned into glutamate using what enzyme?

A

carbamoyl phosphate synthetase II

20
Q

The formation of carbamoyl phosphate and glutamate occurs in the (cytoplasm/mitochondria), which is different from the urea cycle which takes place in the (cytoplasm/mitochondria)

A

cytoplasm, mitochondria

21
Q

In the formation of carbamoyl phosphate, nitrogen is taken from _____ but int he urea cycle, the nitrogen is taken from _____ released from glutamine

A

glutamine, ammonia

22
Q

The formation of N-carbamoylaspartate is catalyzed by what enzyme?

A

aspartate transcarbamoylase

23
Q

The committed step of pyrimidine is what?

A

The second step

he formation of N-carbamoylaspartate is catalyzed by aspartate transcarbamoylase

24
Q

The feedback of turning aspartate into N-carbamoylaspartate is inhibited by

A

CTP (cytidine 5’-triphosphate)

25
Q

These three components come together to produce what compound?

Glutamine, HCO3-, Aspartate

A

N-Carbamoylaspartate

26
Q

Nucleoside diphosphate turns to deoxyribonucleoside diphosphate using what enzyme? What is its energy source?

A

ribonucleotide reductase

NADPH from Pentose phosphate pathway

27
Q

What is dihydrofolate reductase inhibited by?

A

Methotrexate
Aminopterin
Trimethoprim

28
Q

When going from dTMP to dUMP, what enzyme do we use?

A

Thymidylate synthase

29
Q

When going from dTMP to dUMP, the methyl group donator is the____. What is its energy source?

A

N5N10 methylete-THF,

NADPH

30
Q

Regeneration of N5N10 methylene-THF happens by

A

dihydrofolate reductase & serine-hydroxymethyl tra

31
Q

Guanine and hypoxanthine are formed from what in the salvage pathway of purine synthesis

A

adenine

32
Q

Hypoxanthine + PRPP = what

A

IMP

33
Q

Guanine + PRPP = what

A

GMP

34
Q

Adenine + PRPP = what

A

AMP

35
Q

ADA deficiency causes what

A

SCID

36
Q

XO (xanthine oxidase) inhibitors are a good treatment for what condition

A

gout

37
Q

Buildup of Uric Acid from AMP and GMP causes what disease?

A

Gout

38
Q

ADA (adenosine deaminase) stops the formation of ____ from ____

A

inosine, adenosine

39
Q

Xanthine Oxidase (XO) contributes ___ to uric acid

A

OH

40
Q

What type of autosomal disorder is Lesch-Nyhan Syndrome

A

Rare x-linked recessive disorder

41
Q

Lesch-Nyhan is caused by a complete lack of

A

HGPRT

42
Q

In Lesch-Nyhan, the brain becomes dependent on what pathway to produce nucleotides?

A

salvage pathway

43
Q

What two mechanisms can lead to elevated serum urate?

A

Hyperactive PRPP Synthetase
and
Partial lack of HGPRT

44
Q

Excess PRPP accelerates purine biosynthesis

A

Hyperactive PRPP synthetase

45
Q

Reduced salvage pathway; also leads to excess PRPP and accelerated purine synthesis

A

Partial lack of HGPRT

46
Q

Excess PRPP leads to

A

elevated serum urate, or gout

MCBM EXAM 4 (9 decks)

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