Q. 17.2 - An Introduction to General, Organic, and Biological Chemistry

Question

Identify each of the following bases as a purine or a pyrimidine:

(part a). guanine

(part b).  

Step-by-Step Solution

Answer

(part a)  Guanine is determined as a purine base 

(part b)  The component represented is identified as cytosine which is determined as a pyrimidine base

(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 (data-custom-editor="chemistry" $\mathrm{A}$) and guanine (data-custom-editor="chemistry" $\mathrm{G}$) are purine bases, while thymine (data-custom-editor="chemistry" $\mathrm{T}$) and cytosine (data-custom-editor="chemistry" $\mathrm{C}$) are pyrimidine bases (data-custom-editor="chemistry" $\mathrm{C}$). Thymine is replaced by pyrimidine uracil in RNA (data-custom-editor="chemistry" $\mathrm{U}$).

(part a) Step 3 : Introduction

The objective is to identify whether the component is purine base or pyrimidine base

(part a) Step 4 : Explanation

(a) Guanine ($\mathrm{G}$) is a purine base found in DNA that base pairs with cytosine     ($\mathrm{C}$).

(part b) Step 5 : Introduction

The objective is to identify the component given whether it is purine base or pyrimidine base

(part b ) Step 6 : Explanation

b) 

Cytosine is represented by this structure ($\mathrm{C}$). Cytosine is a pyrimidine nucleotide found in DNA that pairs with guanine to form a base pair.