Q. 17.4 - An Introduction to General, Organic, and Biological Chemistry

Question

Identify each of the bases in problem $17.2$ as a component of DNA only. RNA only, or both DNA and RNA.

Step-by-Step Solution

Answer

Part (a) Guanine is determined as a component of both DNA and RNA

Part (b) Cytosine is determined as a component of both DNA and RNA

Part (a) Step 1 : General Introduction

Nucleic acids are organic macromolecules that are present all over the cell. They were first discovered in the nuclei of cells. Nucleic acids, such as DNA and RNA, are found in all known forms of life. 

One of the components of nucleotide structure is nitrogen bases. Purines and pyrimidines are nitrogen bases that form various nucleotide structures.

Part (a) Step 2 : Purine and pyrimidine

Pyrimidines are heterocyclic chemical compounds with two nitrogen atoms at positions 1 and 3 in the ring (single ring). Purines are heterocyclic chemical compounds in which the pyrimidine ring joins the imidazole ring (which has two rings) to form purines. Adenine ($\mathrm{A}$) and guanine ($\mathrm{G}$) are purine bases, while thymine ($\mathrm{T}$) and cytosine ($\mathrm{C}$) are pyrimidine bases ($\mathrm{C}$). Thymine is replaced by pyrimidine uracil in RNA ($\mathrm{U}$).

Part (a) Step 3 : Explanation

Guanine - Guanine ($\mathrm{G}$) is a purine base that can be found in both DNA and RNA and pairs with cytosine ($\mathrm{C}$).

Part (b) Step 1: Explanation

Cytosine is represented by this structure ($\mathrm{C}$). Cytosine is a pyrimidine base that partners with guanine and is found in both DNA and RNA.