BIOCHEMISTRY - L. Stryer - 1984

VOLUME 2

PART III. BIOSYNTHESIS OF MACROMOLECULAR PRECURSORS

CHAPTER 21. BIOSYNTHESIS OF AMINO ACIDS AND HEME

PROBLEMS

1. Write a balanced equation for the synthesis of Alanine from glucose.

2. Through what intermediates does a nitrogen atom pass from N2 to heme?

3. Which tetrahydrofolate derivative is involved in each of the following conversions?

a) Glycine → Serine.

b) Histidine → Glutamate.

c) Homocysteine → Methionine.

4. In the reaction catalyzed by Glutamine Synthetase, an oxygen atom is transferred from the side chain of glutamate to orthophosphate, as shown by studies using 18O-labeled oxygen. Propose an explanation for this experimental finding.

5. Isovaleric acidemia is an inherited disorder of leucine METABOLISM caused by a deficiency of isovaleryl-CoA dehydrogenase. Many infants with this condition die within the first month of life. Recently, it was reported that the administration of large amounts of glycine to two affected children led to a significant improvement in their clinical condition. What is the biochemical basis for treating this disorder with glycine?

6. Nitrogenase catalyzes The formation of HD in the presence of D2, a strong reductant, and ATP. Furthermore, the H-D exchange depends on the presence of N2. What intermediates in N2 fixation might account for these observations?

7. In the absence of ammonium salts or nitrates, blue-green Algae form heterocysts. Heterocysts lack nuclei and are attached to adjacent vegetative Cells. Heterocysts contain an active Photosystem I but completely lack Photosystem II. What is The Role of heterocysts?



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