Humboldt State University ® Department of Chemistry

Richard A. Paselk

 Chem 432

 Exam I


 Spring 1996

 (100 pts)

(15) 1. a. Outline the biosynthesis of lanosterol from acetyl CoA, emphasizing the strategy involved. Indicate the number of carbons in each intermediate


b. Write the reactions, including structures, for the synthesis of lanosterol from squalene.


(20) 2 a. Label the diagrams below to indicate the biosynthetic origins of all of their atoms. (Note - chirality is not correctly indicated on these structures.)



b. Compare/contrast the strategies used in the biosynthesis of these compounds


c. How is purine biosynthesis controlled in prokaryotes - give a diagram with explanatory notes.


(15) 3. Briefly outline/describe the process of nitrogen excretion in birds, beginning with amino acids. Include branchpoints and intermediaries connecting pathways etc. (What major reactions and/or pathways are involved - what is the final excretory product?)


(8) 4. Discuss what occurs in terms of amino acid metabolism during starvation and how it relates to glucose use and availability.


(20) 5. What is the P/O ("P to O ratio") for the conversion of ilu to propionyl CoA and CO2 (via acetyl CoA)? Show calculations/reasoning for credit! (Set up a table similar to those we've used for ATP equivalents in glycolysis, etc.)


(15) 6. a. Show the reactions for the following synthesis:

serine + CO2 + NH2 2 glycine


You may use an abbreviated structure for the H4Folate molecule.


b. Outline (words or symbols) how serine could be used to provide all of the carbons required to synthesis creatine


(7) 7. Diagram/discuss the control of glutamine synthase in E. coli. Why is this enzyme so carefully controlled?


Pathway Diagrams

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Last modified 16 January 2008