Chapter 26, Problem 26.22UKC

Combine the following structures to create a ribonucleotide. Show where water is removed to form an N-glycosidic linkage and where water is removed to form a phosphate ester. Draw the resulting ribonucleotide structure, and name it.

Interpretation Introduction

Interpretation:

The ribonucleotide structure has to be predicted and named.

Concept Introduction:

Composition of nucleic acid: Nucleic acid is a polymer of nucleotides. Each nucleotide has three parts: a sugar, a nitrogenous base, and a phosphate group.

Sugar: In both DNA and RNA, sugar portion is found. In DNA, the sugar is D-ribose, where at 2’hydroxyl group is absent and in RNA, the hydroxyl group is present at 2’.

Nitrogenous bases: Five types of nitrogenous bases (has unique one-letter code A, G, T, U, and C) are derived from two parent compounds called purine and pyrimidine. The purine derivatives are Adenine and Guanine are two fused rings. The pyrimidine derivatives are six-membered nitrogen containing ring. Adenine, Guanine, Thymine, and Cytosine are the nitrogenous bases present in DNA. Adenine, Guanine, Cytosine and Uracil are the nitrogenous bases present in RNA.

Nucleotide: (Nucleoside + phosphate)

Nucleotides are the building blocks of nuclei acids; monomers of DNA and RNA polymers. At carbon-5’ of the ribose sugar, a phosphate group is added which is collectively known as nucleotide. Phosphate groups can be added to any of the nucleotide to form diphosphate or triphosphate.

Nucleoside and its naming: The combination of monosaccharide (sugar) and nitrogenous base is known as nucleoside. The nucleoside names are the nitrogenous base name modified with criteria. While naming nucleoside of purine derivatives the suffix ‘-osine’ is included and for pyrimidine derivatives the suffix ‘-idine’ is used. No prefix used for the nucleosides containing ribose and the prefix ‘deoxy-’ is used for deoxyribose.

Naming nucleotide: At the end of the nucleoside, phosphate group is added. For example, 5’-monophosphate means adding one phosphate group at 5’carbon in the sugar ring.

Numbering the atoms in sugar and base rings:

In order to distinguish the atoms in the sugar of a nucleoside and atoms of a base ring, numbers without prime is used for atoms in the base ring and numbers with prime used for the atoms in the sugar ring.

Answer to Problem 26.22UKC

The structure is,

Explanation of Solution

The nucleotide structure is a combination of nucleoside [ribose (presence of –OH group at 2’ carbon atom in the sugar ring) and guanine base (derivative of purine parent)]. The nucleoside name is the nitrogenous name itself; thus, name is Guanine. Looking at the criteria the name of nitrogenous base is modified as follows, the suffix ‘-osine’ is used for the purine derivatives, as here it is Adenine to Guanosine.

Therefore, the structure of given Guanosine 5’-monophosphate is,

Conclusion

The ribonucleotide structure is predicted and named.