Biochemistry Nucleotide Chemistry and Metabolism

Question 1

Which of the following nitrogenous bases is classified as a purine?

Accepted Answer

Adenine

Answer

Cytosine

Answer

Uracil

Answer

Thymine

Question 2

What distinguishes a nucleotide from a nucleoside?

Accepted Answer

Nucleotides contain one or more phosphate groups; nucleosides do not

Answer

Nucleosides contain a phosphate group; nucleotides do not

Answer

Nucleosides contain deoxyribose; nucleotides contain ribose

Answer

Nucleotides are found only in DNA; nucleosides are found only in RNA

Question 3

In the DNA double helix, adenine forms hydrogen bonds with which complementary base?

Accepted Answer

Thymine

Answer

Guanine

Answer

Cytosine

Answer

Uracil

Question 4

Which pyrimidine base is present in RNA but absent from DNA?

Accepted Answer

Uracil

Answer

Thymine

Answer

Cytosine

Answer

Hypoxanthine

Question 5

De novo purine nucleotide synthesis begins with which metabolite as the core scaffold?

Accepted Answer

Ribose-5-phosphate

Answer

Hypoxanthine

Answer

Xanthine

Answer

Inosine monophosphate (IMP)

Question 6

Lesch-Nyhan syndrome results from a deficiency of which enzyme in purine metabolism?

Accepted Answer

Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)

Answer

Adenosine deaminase

Answer

Purine nucleoside phosphorylase

Answer

Xanthine oxidase

Question 7

What is the final end product of purine catabolism in humans?

Accepted Answer

Uric acid

Answer

Allantoin

Answer

Xanthine

Answer

Hypoxanthine