Neucloetides Metaboilism- week 4

Question 1

Nucloetide vs side

Nucleic acid?

Answer 1

Side- sugar and base
Tide- sugar base and phosphate

Nucleic acid- chain of nucloetides

Question 2

Purines vs Pyridines

Answer 2

Purines- A and G

Pyridines- C, U , T

Question 3

What bases and sugar does DNA use? RNA?

Answer 3

DNA- deoxyribose- A, T, C, G

RNA- ribose A, U, C and G

Question 4

Functions of Nucleotides

Answer 4

1. Building block for DNA and RNA
2. Energy supply from high energy P-P (ATP and GTP)- quick through hydrolyzation
3. Coenzymes that have nucleotide portion- NAD, NADP, FAD, CoA
4. Ingredients for active metabolic precursors
5. Physiological Mediators- Signal transduction (GTP), cAMP, Adenosine (regulates blood flow),
6. Allosteric effectos of metabolic enzymes

Question 5

Source of nucleotide

Answer 5

1. Diet (5%)- plants/animals- anything with cells
2. De novo synthesis
3. Salvage from existing bases (majority)- because synthesis purines and pyridines is expensive

Question 6

Exmaple the digestion of DNA/Nucleic Acids

Answer 6

Nucleotides- denatured in the stomach but mostly digested by pancreatic enzymes

Nucleases make oligonucleotides
Phosphodiesterases- mononucleotides
Nucleotidases make nucleosides
Nucelsidases make- base

Question 7

Absorption of Nucleic Acids

Answer 7

Sugars (most absorbed and reused to PPP or channeled to glycolysis) taken up by intestinal mucosal cells and enter circulation

Bases- only 5% enter circulation because mucosal cells degrade them so they are converted to uric acid and excreted. This is why we need salvage and de novo synthesis because we excrete what comes in from diet

Question 8

Disorders in Nucleotides Metabolism

Answer 8

Gout- purine synthesis or degradation

Lesch-nyhan- defecnt in purine salvage

Orotic aciduria- defect in de novo pyriminidine synthesis

CMB agents- drugs that block de novo pathways are successfully used as chemo agents

Question 9

Rate limiting step of purine de novo snthesis

Answer 9

PRPP—glutamine phosphoribosyl amidotransferase–> IMP

Down regulated by IMP, AMP, GMP (downstream products)

upregulated by PEPP

Question 10

Methotroxeate

Answer 10

Acts on steps where formyl THF is needed- this is a component of purine synthesis so this drug stops purine synthesis

Question 11

What does myochenolic acid do

Answer 11

It inhibts IMP DH so does not allo T and B cells to form

Question 12

What enzyme is regulated in purine degradation? What drug treats it?

Answer 12

Xanthine Oxidase- this enzyme can take electrons nad protons to the electron transport chain and is the one means of energy from purine degradation

Can be inhibited by allopurinol and this drug is given to ppl who have accumulation of uric acid because hypoxanthine and xanthine are easier to excrete

Question 13

Consequences of gout

Treatments

Answer 13

Acute inflmmation and kidney stones

Colchicine- acts on leukocytes and tappers down inflmmatio doesn’t solve the main problem

Urisouric acid- help promote excretion of uric acid

Alloputurinol- inhibit xanthineoxidase which decrease the amount of uric acid produce and allow purines to be secreted as hypoxanthine and xanthine

Question 14

What two enzymes are important in the salvage pathway

Answer 14

HGRTase and APRTase

Hypoxanthine– HGRTase—> IMP

Gaunine— HRGTase–> GMP

Adenine— APRTase–> AMP