11) Tetrahydrofolate (THF) and its derivatives shuttle between different substra

Question

11) Tetrahydrofolate (THF) and its derivatives shuttle between different

substrates.

a) electrons

b) H+

c) acyl groups

d) one carbon units

e) NH2 groups

12) The ribosyl phosphate moiety needed for the synthesis of orotidylate,

inosinate, and guanylate is provided most directly by:

a) 5-phosphoribosyl 1-pyrophosphate.

b) adenosine 5'-phosphate.

c) guanosine 5'-phosphate.

d) ribose 5-phosphate.

e) ribulose 5-phosphate.

13) Which one of the following statements is true of the biosynthetic pathway for

purine nucleotides?

a) CO2 does not participate in any of the steps in this pathway.

b) Deoxyribonucleotides are formed from 5-phosphodeoxyribosyl 1-pyrophosphate.

c) Inosinate is the purine nucleotide that is the precursor of both adenylate and

guanylate.

d) Orotic acid is an essential precursor for purine nucleotides.

e) The amino acid valine is one of the precursors contributing to purine nucleotides.

14) De novo purine biosynthesis is distinguished from de novo pyrimidine

biosynthesis by:

a) condensation of the completed purine ring with ribose phosphate

b) incorporation of CO2.

c) inhibition by azaserine (a glutamine analog).

d) participation of aspartate.

e) participation of PRPP (phosphoribosyl pyrophosphate).

Chem 4413 Homework 1 Spring 2014

15) Glutamine is a nitrogen donor in the synthesis of:

a) CTP.

b) dTTP.

c) inosinic acid (IMP).

d) orotate.

e) UMP.

Explanation / Answer

1.d) one carbon units

2.a) 5-phosphoribosyl 1-pyrophosphate.

3.a) CO2 does not participate in any of the steps in this pathway.

4.b) incorporation of CO2.

5.a) CTP.

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