Q. 17.3 - An Introduction to General, Organic, and Biological Chemistry

Question

Identify each of the bases in problem $17.1$ as a component of DNA only, RNA only, or both DNA and RNA.

Step-by-Step Solution

Answer

Part (a) Thymine is determined as a component of DNA only.

Part (b) Adenine is determined as a component present in 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

Thymine - Thymine ($\mathrm{T}$) is a pyrimidine base that only exists in DNA and pairs with adenine ($\mathrm{A}$). Thymine is replaced by uracil in RNA ($\mathrm{U}$).

Part (b) Step 4 : Explanation

Adenine is represented by the structure ($\mathrm{A}$). The purine base adenine is found in both DNA and RNA. Adenine base partners with thymine ($\mathrm{T}$) in DNA, whereas adenine base pairs with uracil in RNA ($\mathrm{U}$).