Lecture 25 - Nucleotide Metabolism

Question 1

Name the digestion products of polynucleotides.

Answer 1

1. purines
2. pyramidines
3. ribose
4. deoxyribose
5. phosphate

Question 2

What are the 3 steps in the biosynthesis of purines?

Answer 2

a) Synthesis of PRPP
b) Synthesis of IMP (committed and regulated step)
c) Synthesis of adenosine (by adenosine monophosphate) and guanosine (by guanosine monophosphate)

Question 3

What is the committed step in the biosynthesis of purines?

Answer 3

Synthesis of IMP

Question 4

What are the 3 steps in the biosynthesis of pyrimidines?

Answer 4

a) Synthesis of carbamoyl-phosphate by CPS-II: Key regulated step of pyrimidine biosynthesis (inhibited by UTP)
b) Synthesis of Orotate and UMP
c) Synthesis of UTP, CTP

Question 5

What is the key regulated step in the biosynthesis of pyrimidines?

Answer 5

Synthesis of carbamoyl-phosphate by CPS-II: Key regulated step of pyrimidine biosynthesis (inhibited by UTP)

Question 6

Pyrimidine biosynthesis is inhibited by ________.

Answer 6

UTP

Question 7

PPAT regulates a step in the synthesis of:

Answer 7

IMP (from substrate PRPP in initial step)

Question 8

Thymidylate synthase is inhibited by __________, which is used to treat a variety of cancer.

Answer 8

5-fluoruracil

Question 9

_________ is a guanine analog that is used to treat herpes simplex 1 infections.

Answer 9

Acyclovir

Question 10

__________ is an inhibitor of inosine monophosphate dehydrogenase.

A. Methotrexate
B. Sulfonamide
C. Mycophenolic acid

Answer 10

C

Question 11

________ is a competitive inhibitor of dihydrofolate reductase, an enzyme needed to regenerate THF.

A. Methotrexate
B. Sulfonamide
C. Mycophenolic acid

Answer 11

A