Nucleotide Metabolism

Front 1

True or False: The nitrogenous bases of nucleotides and nucleosides are of two types - the purines, which are heterocycles containing six atoms, and pyrimidines, which are heterobicycles containing nine atoms.

Back 1

False

Front 2

True or False: Nucleotide biosynthesis occurs only in cells that undergo replication.

Back 2

False

Front 3

True or False: To synthesize the purine ring, liver cells require metabolic sources of glycine, formate, glutamine, CO2, and aspartate.

Back 3

True

Front 4

True or False: In purine nucleotide synthesis, the purine ring is synthesized and then attached to ribose 5-phosphate to make nucleotides.

Back 4

False

Front 5

True or False: Inosine 5'-monophosphate (IMP) is an intermediate from which both 5'-AMP and 5'-GMP are synthesized.

Back 5

True

Front 6

True or False: To synthesize GMP from IMP, ATP is required, whereas to synthesize AMP from IMP, GTP is required.

Back 6

True

Front 7

True or False: To synthesize the pyrimidine ring, liver cells require asparagine, glutamate, and bicarbonate.

Back 7

False

Front 8

True or False: The first step in the pyrimidine ring biosynthesis involves formation of carbamoyl phosphate, catalyzed by carbamoyl phosphate synthetase. This is the same enzyme that operates in the urea cycle.

Back 8

False

Front 9

True or False: Uric acid, an avian excretion product, is a pyrimidine.

Back 9

False

Front 10

True or False: Orotate is the end product of the pyrimidine biosynthetic pathway and is the derivative from which the pyrimidine nucleosides and nucleotides are made.

Back 10

False

Front 11

True or False: The disease gout is the result of excess amounts of uric acid.

Back 11

True

Front 12

True or False: dTMP is formed by the reduction of the ribose moiety of ribothymidylate.

Back 12

False

Front 13

True or False: Most free purine and pyrimidine molecules are salvaged, but some are catabolized. Catabolism of both purine and pyrimidine molecules leads to the excretory product uric acid.

Back 13

False

Front 14

The components of a nucleotide are a/an ___, a/an ___, and ___.

Back 14

purine or pyrimidine base; ribose or deoxyribose; one or more phosphate groups

Front 15

The active form of ribose 5-phosphate required for nucleotide biosynthesis is ___.

Back 15

5-phosphoribosyl 1-pyrophosphate

Front 16

In the liver cells, the location of purine biosynthesis is ___.

Back 16

the cytosol

Front 17

During purine nucleotide synthesis, the first reaction of 5-phosphoribosyl 1-pyrophosphate is the addition of nitrogen to the ribose residue. The source of this nitrogen is ___.

Back 17

glutamine

Front 18

Carbamoyl phosphate is involved in the biosynthesis of which type of nucleotides, the pyrimidines or the purines?

Back 18

pyrimidines

Front 19

The recycling of products from the normal cellular breakdown of nucleic acids is an energy-conserving process called ___.

Back 19

salvage

Front 20

A common treatment for gout, allopurinol works by inhibiting xanthine oxidase. Instead of producing ___, the two more soluble products of purine metabolism ___ and ___ are excreted.

Back 20

uric acid; xanthine; hypoxanthine

Front 21

CTP is formed from UTP by transformation of the keto group at C-4 of the pyrimidine ring to an amino group. The source of the nitrogen for this amino group is ___ that is converted to ___.

Back 21

glutamine; glutamate

Front 22

Anticancer drugs such as 5-fluorouracil and methotrexate prevent the synthesis of ___.

Back 22

dTMP