Amino Acid Biosynthesis

Study Questions



Non-essential Amino Acids


1. Discuss the significance of a-ketoglutarate as an activator of Glutamine Synthetase, both in mammals and in bacteria.


2. The four intermediates of the Urea Cycle are a-Amino Acids.  Which of these is considered an essential amino acid? Outline a pathway by which adults can synthesize this amino acid from 1 glucose molecule.


3. Many biosynthetic processes involve the addition of a C1 until to a metabolic precursor. Study the structure of THF, which has the ability to tranfer C1 units  in different oxidation states. Understand how (where) to attach C1 subunits in different oxidation states.


4. Identify the common intermediates from which the non-essential amino acids are derived. Make sure that you know the names of the amino acids in each group, and know the pathway in which each of the intermediates is found.


5. Chorismate is the seventh intermediate in the synthesis of tryptophan from PEP and erythrose-4-phosphate. Why is it considered a branch point in amino acid synthesis?





Essential Amino Acids (for mammals)


1. Identify the common intermediates from which the essential amino acids are derived. Explain why Tyrosine is really an essential amino acid (show pathway). Make sure that you know the name of each amino acid in each group, and the pathway in which each intermediate is found.


2. Explain the differential control of aspartokinase enzymes in E. coli.


3. Discuss the role of hydroxyethyl-TPP at the first branch point in the synthesis of Leu, Ile, and Val on a mechanistic/chemical basis.


4. Explain the phenomenon of channeling, using the Tryptophan Synthase reaction.  What are the advantages of channeling?


5. One of the symptoms of Kwashiorkor, the dietary deficiency disease in children, is depigmentation of skin and hair. Explain the biochemical basis for this symptom.



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