Class 5: Nucleotide Metabolism

Question 1

nucleoside

Answer 1

nitrogen base + sugar

Question 2

nucleotide

Answer 2

nitrogen base + sugar + phosphate

Question 3

3 components of nucleotide

Answer 3

1) nitrogen containing base: purine or pyrimidine

2) pentose (sugar)

3) phosphate groups

Question 4

Name the purines

Answer 4

adenine
guanine

Question 5

name the pyrimidines

Answer 5

cytosine
thymine
uracil

Question 6

difference between DNA and RNA nucleotides

Answer 6

Base: Thymine for DNA, Uracil for RNA

Sugar: Deoxyribose for DNA, ribose for RNA

Question 7

De novo pathways

Answer 7

base itself is synthesized from simple starting materials

Question 8

salvage pathways

Answer 8

bases are recovered and attached to an activated ribose
- dominant pathway

Question 9

how is the purine ring constructed

Answer 9

it is constructed by a series of reactions that add carbons and nitrogen to performed ribose 5-phosphate

Question 10

Synthesis of purine necleotides

Answer 10

1) Synthesis of 5-phosphoribosyl-1-pyrophosphate (PRPP)

2) Synthesis of 5’-phosphorybosylamine

3) Synthesis of inosine monophosphate (IMP)

Question 11

azathioprine

Answer 11

immune suppressive cancer drug
- inhibitor of purine synthesis

Question 12

Hypoxanthine-guanine phosphoribosyltransferase

Answer 12

transfer phosphoribose into ??

Question 13

leach-nyhan syndrome

Answer 13

• deficiency of HGPRT
  1) Increased PRPP and decreased IMP and GMP, increased de novo purine synthesis.
  2) Increased breakdown of purine, therefore, increased uric acids.

Question 14

Sources if purine necleotides

Answer 14

1) Dietary purine
2) Tissue nucleic acids
3) Endogenous purine synthesis

Question 15

end product of purine nucleotides

Answer 15

uric acids

Question 16

Adenosine Deamniase

Answer 16

Convert adenosine into inosine
- ADA deficiency causes severe combined immunodeficiency

Question 17

Adenosine Deaminase Deficiency

Answer 17

does not produce uric acid
leads to deoxyadenosine -> dATP -> ribonucletoide reductase -> inhibition of DNA synthesis with increased T and B cell apoptosis -> severe combined immunodeficiency

Question 18

Gout

Answer 18

high levels of uric acid in the blood due to under excretion or overproduction of uric acid

Question 19

Causes of Gout

Answer 19

1) Abnormal PRPP synthetase activity
2) Defect in purine salvage pathway
3) alcohol

Question 20

Treatment for glout

Answer 20

prevention of the deposition of rate crystals
1) colchine: decrease the movement of the granulocytes into the deposition area
2) allopurinol: analog of hypoxanthine, inhibitor of xanthine oxidase
3) Probenecid and sulfinpyrazone

Question 21

pyrimidine synthesis

Answer 21

1) formation of carbamoyl phosphate

Question 22

orotic aciduria

Answer 22

……..

Question 23

THF(FH4) in AA metabolism

Answer 23

1) degradation of histidine
2) Serine synthesis
3) Resynthesis of methane from homocysteine

Question 24

primary one carbon carrier

Answer 24

its purpose is to carry and transfer the oxidation state of one carbon unit

Question 25

conditions from folate deficiency y

Answer 25

1) metabolic anemia

2) neural tube defects: folate deficiency inhibits DNA synthesis and can lead to neural tube defects early pregnancy