MCM - Nucleotide Metabolism

Question 1

Nucleosides vs. Nucleotides

Answer 1

Nucleosides have a Base and a Sugar

Nucleotides have: Base, Sugar, and Phosphate

Question 2

How is Adenine bonded with the Ribose Sugar

Answer 2

Via a Glycosidic Bond

Question 3

How many Carbons does a Purine have in its ring

Answer 3

9

Question 4

How many carbons does a Pyrmadine have in its carbon ring

Answer 4

6

Question 5

Which bases are in DNA

Answer 5

Adenine
Guanine
Cytosine
Thymine

Question 6

Which bases appear in RNA

Answer 6

Guanosine
Uracil
Adenine
Cytosine

Question 7

What are some other roles of Nucleosides and Nucleotides

Answer 7

ATP & GTP

Cosubstrates

Components of Co-Factors
CoA
FAD
FMN
UDP-Glc
NAD⁺
NADP⁺

Regulatory Role
cAMP
gAMP
m7GTP

Important Biomolecules;
Vitamin B₁₂

Question 8

Are the carbon sources for Purine and Pyrmadine Ring formation the same

Answer 8

No

Question 9

Purine Synthesis Basic Steps

Answer 9

Sugar Molecule Synthesis

AND THEN

Ring Formation

Question 10

Pyrmadine Synthesis Basic Steps

Answer 10

Ring Formation

AND THEN

Sugar Formation

Question 11

How many phases of De Novo Synthesis does it take to make a Purine

Answer 11

4 stages

Question 12

What are the 4 stages of the De Novo Synthesis for Purine Formation

Answer 12

1. Ribose-5-P Activation; phosphorylation of Ribose-5-P to Phospho-Ribosyl-Pyro-Phosphate (PRPP)
2. Conversion of PRPP to Phosphoribosylamine (PRA); the rate limiting step of the De Novo Synthesis of Purines
3. Conversion of PRA to an Inosine Monophosphate (IMP) (Ring)
4. Conversion of IMP to Adenosine or Guanosine

Question 13

What does Methotrexate inhibit in the De Novo Synthesis

Answer 13

The synthesis of the IMP ring for Purine Synthesis

Question 14

What is IMP converted to

Answer 14

Guanosine
or
Adenosine;

Depending on GMP/AMP Levels

Question 15

Sulfa drugs effect on Folate

Answer 15

Inhibit the Bacterial DHPS and DHFR; so the bacterial, viral, or fungal cells cannot make folate from PABA

Question 16

What is the feedback inhibition on the De Novo Synthesis of Purines

Answer 16

Accumulation of PRPP
Accumulation of PRA
Accumulation of GMP/AMP

Question 17

What is the rate limiting step in the synthesis of Pyrmidine Ring

Answer 17

Carbamoyl Phosphate + Aspartate —>
Carbamoylaspartate

Enzyme: Aspartate Transcarbamoylase

Question 18

How many Steps is the Synthesis of a Pyrmidine

Answer 18

3 Steps

Question 19

What are the Steps of synthesizing a Pyrmidine Ring

Answer 19

1. Fabrication of orotate ring
2. Attachment of PRPP to form UMP
3. Convert UMP to uridine, cytosine, and thymidine

Question 20

What are the two major regulatory steps in Pyrmidine Synthesis

Answer 20

Carbamoyl Phosphate Synthetase

And

Aspartate Transcarbamoylase

Question 21

What inhibit Carbamoyl Phosphate Synthetase

Answer 21

UMP
And
Purines

Question 22

What Stimulates Carbamoyl Phosphate Synthetase

Answer 22

PRPP

Question 23

What does CTP Inhibit via Feedback Inhibition

Answer 23

Aspartate Transcarbamoylase

Question 24

What is the cancer drug for Pyrmidine Synthesis

Answer 24

Adrucil
(5-Fluorouracil)

Mechanism not clear; likely inhibits Thymidylate Synthase

Question 25

What are the two defective enzymes in Oroctic Aciduria

Answer 25

Orotate phosphoribosyl transferase and Oritidine Carboxylase

Question 26

How does Acyclovir work

Answer 26

Acts as a Nucleoside; which binds a phosphate Leads to DNA Polymerase being blocked by a false nucleotide; the name of the kinase that is blocked is Thymidine Kinase, only in virally infected cells

Question 27

What is Acyclovir generally used for

Answer 27

Herpes Lesions and Chicken Pox

Question 28

Where does Pyrmidine Synthesis Occur

Answer 28

In the Cytosol And The Mitochondria

Question 29

What do Ribonucleases do

Answer 29

Convert RNA to short oligomers

Question 30

What do Deoxyribonucleases do

Answer 30

Convert DNA to short oligomers

Question 31

What do Phosphodiesterases do

Answer 31

Convert short oligomers to NMP's or dNMP's

Question 32

What does a Nucelotidase do

Answer 32

Converts dNMP/NMP into nucelosides and deoxynucelosides

Question 33

What do Nucleosidases do

Answer 33

Remove Ribose group and converts them into Pyrmidines or Purines

Question 34

What is Uric Acid a product of

Answer 34

Purine Nucleotide Catabolism

Question 35

What does a build up of Adenosine Deaminase do

Answer 35

Causes hemolytic anemia

Question 36

What does underproduction of Adenosine Deaminase do

Answer 36

Associated with the second most common form of sever combined immunodeficiency (SCID)

Question 37

What is Gout caused by

Answer 37

A build up of Uric Acid from eating to many high protein foods and drinking too much wine

Question 38

How are Uric Acid Crystal Formed

Answer 38

Urate binds with sodium to make Monosodium Urate; which is not water soluble This precipitates out of solution are forms Uric Acid Crystals

Question 39

What does Pyrmidine Nucleotide Catabolism Produce

Answer 39

Malonyl-CoA; Can go into Fatty Acid Synthesis or Methylmalonyl-CoA and Succinyl-CoA; Can go into TCA Cycle

Question 40

What is used in the Catabolism of Pyrmidine Nucleotides to determine DNA Turnover

Answer 40

ß-Aminoisobutyrate

Question 41

What is the Pyrmidine Nucleotide Salvage Pathway

Answer 41

Takes Pyrmidines to their respective -TP molecule

Question 42

What is the Purine Salvage Pathway

Answer 42

Takes a Purine into their respective -MP

Question 43

Lesch-Nyhan Syndrome Cause

Answer 43

Defect in the HGPRT enzyme in the Purine Salvage Pathway

Question 44

What does the defect in HGPRT Produce in Lesch-Nyhan Syndrome

Answer 44

Overproduction of Uric Acid

Question 45

How do patients present with Lesch-Nyhan Syndrome

Answer 45

Hyperuricemia and Hyperuricosuria

Question 46

What are the symptoms of Hyperuricemia and Hyperuricsuria

Answer 46

Urate Kidney Stones, Poor Muscle Control, Mental Retardation, and tendency FOR SELF MUTILATION