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Biochemistry 2 > Ch 23 > Flashcards

Ch 23 Flashcards

1
Q

Nucleobase

A

A, T, G, C, or U

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2
Q

Nucleoside

A

Nucleobase + sugar

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3
Q

Nucleotide

A

Nucleobase + sugar + phosphate

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4
Q

What does purine and pyrimidine biosynthesis require?

A

Ribose-5-phosphate (R5P)

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5
Q

what is the conversion of Ru5P to R5P catalyzed by?

A

ribulose-5-phosphate isomerase

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6
Q

What does purine synthesis yield?

A

Inosine monophosphate

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7
Q

What is the ATP dependent step of purine synthesis?

A
  1. Activation of ribose-5-phosphate
  2. Acquisition of purine atoms C4, C5, and N7 (reversible)
  3. Acquisition of purine atom N3
  4. Formation of purine imidazole
    7.
    8.
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8
Q

What is the comitted step of purine synth?

A
  1. Acquisition of purine atom N9 (committed step)
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9
Q

What is the cost of generating IMP

A

6× ATP
▪ 2× Formyl-THF
▪ 2× Glu
▪ 1× Gly
▪ 1× Asp

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10
Q

Which reactions in purine synthesis are regulated?

A

first 2. The first one is inhibited by ADP and GDP and the second is inhibited by ATP/ADP/AMP &
GTP/GDP/GMP & allosterically activated
by PRPP

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11
Q

waht are purines derived from ?

A

 Gly
 Asp
 Gln
 Formate
 Bicarbonate

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12
Q

What competitively inhibits IMP?

A

AMP and GMP

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13
Q

What increases the rate of GMP and AMP snth

A

Rate of GMP synthesis increases with
[ATP]

rate of AMP synthesis increases
with [GTP]

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14
Q

What happens in AMP formation?

A
  1. Asp condensation
    − GTP-dependent
  2. Fumarate elimination
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15
Q

What happens in GMP formation

A
  1. Dehydrogenation
    − NAD+-dependent
  2. Amine transfer
    − ATP-dependent, Gln hydrolyzes to Glu
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16
Q

What does pyrimidine synth yield?

A

UMP

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17
Q

What catalyzes the first purine synth reaction?

A

Ribose phosphate pyrophosphokinase

18
Q

What catalyzes second reaction?

A

Aminodophosphoribosoyl transferase

19
Q

What is GMP synth activated by?

20
Q

What is AMP synth activated by?

21
Q

What is pyrimidine biosynth derived from?

A

Gln, Asp, Bicarbonate

22
Q

What steps in UMP synth are ATP dependent?

A
  1. Carbamoyl phosphate synthesis
23
Q

What cofactors is UMP synth dependent on?

A

FMN and non-heme Fe

24
Q

What is the conversion of UMP to CTP dependent on what happens?

A

ATP dependent. Amine transfer reaction wher e Gln hydrolyzes to Glu.

25
What converts UMP to UDP and UTP?
nucleoside kinases. THey add a phosphate group to
26
What converts UTP to CTP and waht does it require?
CTP synthetase. requires 2 ATP and 1 glutamine
27
What converts UDP to dUDP?
Ribonucleotide Reductase (RNR)
28
What converts dUMP to dTMP
thymidylate synthase
29
what is the conversion of dUMP to dTMP dependent on?
MTHF (transfers methyl group)
30
What are the control points in bacteria
aspartate transcarbamoylase (reaction 2)
31
What are the control points in animals for pyrimadine synth
Cabamoyl phosphate synthetase (reaction 1) and OMP decarboxylase (reaction 6)
32
What is the terminal product of Purine catabolism?
Uric acid
33
What converts nucleotides to nucleosides
Nucleotidase. That is step one of purine catabolism
34
What is the second step of purine catabolism?
2. Purine Nucleoside Phosphorylase eliminates Ribose-1-phosphate − Adenosine is deaminated to Inosine first
35
What is the third step of purine catabolism?
3. Xanthine Oxidase (XO) converts Xanthine to Uric Acid − Molybdopterin-dependent enzyme − Hypoxanthine (inosine/adenosine route) is oxidized to Xanthine by XO − Guanine is deaminated to Xanthine by guanine deaminase first
36
What are the steps of catabolism of purine
1. nucleotdie goes to nucleside 2. ribose-1-phosphate is eliminated 3. Xanthine is converted to uric acid
37
what catalyzes step 3? wwhat is it dependent on?
xanthine oxidase (XO). molybdopterine-dependent
38
what is the final product of pyrimidine catabolism?
malonyl-CoA and methylmaolnyl-CoA
39
Explain the steps of pyrimidine catabolism
1. nucleotide to nucloside 2. uridine phosphorylase eliminates ribose-1-phosphate. 3. uricil is reduced. 4. malonyl-COA is formed from transamination and thioesterification reactions
40
What happens to the methylmalonyl-CoA after catabolism of pyrimidiens?
Converts to succinyl COA and enters TCA
41
What happens to malonyl-CoA after catabolism?
Fatty acid biosynthesis is where it enters the

Biochemistry 2 (8 decks)

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