Trans - Metabolism of Nucleotides Flashcards Preview

[OS 201] 3rd Exam > Trans - Metabolism of Nucleotides > Flashcards

Flashcards in Trans - Metabolism of Nucleotides Deck (47)
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1

Examples of Purines (2)

Adenine
Guanine

2

Examples of Pyrimidines (3)

Cytosine
Thymine
Uracil

3

Differentiate a Ribose and a Deoxyribose

Main difference is that the hydroxyl group (OH) at Carbon 2 in ribose is replaced by hydrogen (H) in deoxyribose
Difference renders RNA backbone susceptible to base catalyzed hydrolysis

4

[Nucleoside]

Components

Where is sugar attached in Purines and Pyrimidines?

Base + Sugar

Purine: N-9
Pyrimidine: N-1

5

[Nucleotide]

Components

Where is Phosphate attached in Ribose and Deoxyribose?

Base + Sugar + Phosphate

Ribose: C5 (Possibly C2/C3)
Deoxyribose: C3

7

Nucleotides are joined together via?

Phosphodiester Bonds

8

Polymerization of NAs from Nucleoside Monophosphates occur through?

Dehydration

9

Polymerization of NAs from Nucleoside Triphosphates occur through?

Phosphoanhydride bond destruction and pyrophosphate removal

10

Degradation of NAs occur through?

Hydrolysis of covalent linkages

11

Fate of Sugar and Nitrogenous Bases

Sugar: Absorbed like carbohydrates
Bases: Excreted; Purines are excreted as Uric Acid

12

Are nucleotides essential?

No they are not, the body is capable of synthesizing them

13

Examples of Metabolic Precursors (5)

1. Amino Acids
2. Ribose-5-Phosphate
3. CO2
4. 1-C Groups
5. NH3

14

Pathway of Digestion of Dietary Nucleic Acids

1. Nucleic acids ingested in the form of nucleoproteins - like proteins, denaturated by acidity in the stomach

2. Denatured nucleic acids subjected to nucleases --> result to oligonucleosides (shorter chains

)3. Further cleaved by phosphodiesterase, which cleave phosphodiester bonds one at a time

4. Nucleases and phosphodiesterase cleave oligonucleotides into mononucleotides

5. Nucleotidases dephosphorylate mononucleotides into nucleosides

6. Nucleosidases split the nucleosides further into sugar and base

15

[Purine De Novo Synthesis]

Parent Purine Nucleotides (2)

AMP
GMP

16

[De Novo Synthesis Linear Pathway]

What is the enzyme that catalyzes the rate-limiting step of the pathway?

PRPP Amidotransferase

17

[De Novo Synthesis Linear Pathway

]Why is PRPP Synthetase not the rate-limiting step?

The product, PRPP, can still be used for other reactions

18

[De Novo Synthesis Linear Pathway]

What is the first intermediate with a complete purine ring?

IMP

19

[De Novo Synthesis Branched Pathway]

IMP could be converted to? How?

GMP: NH2 at C2 from Gln, requires ATP

AMP: NH2 at C6 from Asp; requires GTP

20

[De Novo Synthesis Branched Pathway

]Why is ATP invested to produce GMP from IMP while GTP is used to produce AMP?

It is a form of REGULATION. Goal is to have equimolar amounts of AMP and GMP.

21

[Purine De Novo Synthesis

]What is the starting material where atoms are successively added?

PRPP

22

[Purine De Novo Synthesis]

Purine ring is derived from?

PRPP

23

[Purine De Novo Synthesis]

Donors of Atoms to Purine Ring (2)

Amino Acids
1-C Compounds

24

[Purine De Novo Synthesis]

How much ATP used in the process?

5 moles

25

[Purine De Novo Synthesis]

Where does it occur?

Cytosol of the Liver

26

[Pyrimidine De Novo Synthesis]

What is the rate regulated step?

Carbamoyl Phosphate Synthetase II (CPSII)

27

2 Pathways that Lead to Nucleotides

1. De Novo2. Salvage

28

[Pyrimidine De Novo Synthesis]

Compare the two types of CPS by

1. Tissue
2. Cellular Location
3. Pathway
4. Substrate

CPS I
1. Liver
2. Mitochondrial Matrix
3. Urea Cycle
4. NH

CPS II
1. All tissues
2. Cytosol
3. Pyrimidine Synthesis
4. Amide of Gln (Glutamine)

29

[Pyrimidine De Novo Synthesis]

Regulation of CPS II

UPM: Complete Inhibitor
PRPP: Activator

30

[Pyrimidine De Novo Synthesis]

Ring is derived from? (3)

Asp
CO2
Amide of Gln

31

[Salvage Reactions]

What occurs here?

Recycling of free purine/pyrimidine bases and nucleotides released from NA degradation