Solutions For 9780131905429 Chapter 2 Problem 20A

Nucleic acids are the macromolecules that are made up of several repeating monomer units called nucleotides. Nucleotides are joined together by phosphodiester bonds to form a complex nucleic acid like DNA or RNA.

A nucleotide is made up of 3 components. They are a nitrogenous base (can be either a purine or a pyrimidine), pentose sugar (either ribose or deoxyribose), a phosphate group and. A pentose sugar is a 5- carbon sugar and is attached to the phosphate group at one end and to the nitrogenous base at the other end. Nitrogenous bases are broadly classified into two groups namely purines and pyrimidines. Purines include adenine and guanine. Pyrimidines include thymine, cytosine and uracil. Thymine is present only in DNA. It is replaced by uracil in case of RNA.

The sugar in case of RNA is ribose sugar, whereas it is 2-deoxyribose in case of RNA.

The structures of purines and pyrimidines are shown below:

The structures of ribose and deoxyribose are shown below: