Question

Which of the following is not a nucleoside?

• A. Deoxydenosine
• B. Cytidine
• C. Riboflavin
• D. Thymidine

Answer 1

Answer: (C)

Purine and pyrimidine nucleotides polymerize to form nucleic acids. Adenosine, guanosine, thymidine, uridine and cytidine are nucleosides. Nicotinamide and riboflavin nucleotides act as coenzymes of oxidizing enzymes.
A nucleoside is formed by the nitrogenous base and pentose sugar. DNA nucleosides are known as deoxyribose nucleosides while RNA nucleosides are known as ribose nucleosides. Adenylic acid, thymidylic acid, guanylic acid, uridylic acid and cytidylic acid are nucleotides.