Exam 4 Biosynthesis of AA, Nucleotides, Related Molecules

Question 1

Amino Acid Synthesis Overview

Answer 1

• Source of N: Glu or Gln
• Comes from intermediates of: glycolysis, CAC, PPP
• bacteria can synthesize all 20 AA

Question 2

What are the seven precursors of amino acids, and what cycle are they from?

Answer 2

• Citric Acid Cycle: a-ketoglutarate, oxaloacetate
• Glycolysis: pryruvate, 3-phosphoglycerate, phosphoenolpyruvate
• Pentose Phosphate Pathway: ribose 55-phosphate, erythrose -phosphate

Question 3

What amino acids are derived from the precursor, a-Ketoglutarate?

Answer 3

Transamination of a-Ketoglutarate (add NH3)
-> Glutamate -> Glutamine, Proline, Arginine

Question 4

What amino acids derive from the precursor, 3-Phosphoglycerate (Glycolysis)?

Answer 4

3- Phosphoglycerate -> Serine -> Glycine, Cysteine

Question 5

What amino acids are derived from the precursors, Oxaloacetate and Pyruvate?

Answer 5

• Transamination of Oxaloacetate -> Aspartate -> Asparagine, Methionine, Lysine, Threonine
• Pyruvate -> Alanine, Valine, Leucine, Isoleucine

Question 6

What aromatic amino acids are derived from Phosphoenolpyruvate and Erythrose 44-Phosphate?

Answer 6

Phsophoenolyruvate -> Erythrose 4-Phosphate -> Phenylalanine (which can turn into Tyrosine), Tyrosine, Tryptophan
- In order to create double bonds: Rings must be synthesized, closed, then oxidized
- Common Intermediate: Chorismate

Question 7

What derives from the precursor, PPP Metabolite Ribose 5-Phosphate?

Answer 7

Histidine derives from PPP metabolite ribose 5-phosphate?
- PRPP: precursor (activated form of PPP), also starting material for nucleic acid

Question 8

PRPP