Question

Explain the difference in structure between a nucleoside and a nucleotide.

Short answer

Answer: The main difference in structure between a nucleoside and a nucleotide is the presence of one or more phosphate groups in a nucleotide, while nucleosides lack the phosphate group. Both consist of a nitrogenous base and a sugar, but nucleotides have the additional phosphate component.

Step-by-step solution

1. Definition of a Nucleoside

A nucleoside is a molecular building block composed of a nitrogenous base and a sugar (ribose in RNA or 2'-deoxyribose in DNA). The nitrogenous bases can be either purines (adenine and guanine) or pyrimidines (cytosine, thymine, and uracil).

2. Definition of a Nucleotide

A nucleotide is composed of three parts: a nitrogenous base, a sugar (ribose in RNA or 2'-deoxyribose in DNA), and one or more phosphate groups. Like nucleosides, the nitrogenous bases in nucleotides can be either purines (adenine and guanine) or pyrimidines (cytosine, thymine, and uracil).

3. Identifying the Structural Difference

The primary difference in structure between a nucleoside and a nucleotide is the presence of one or more phosphate groups in a nucleotide. Nucleotides contain additional phosphate group(s) attached to the sugar component's 5' carbon. In contrast, nucleosides lack the phosphate group.

4. Summary

To summarize, both nucleosides and nucleotides consist of a nitrogenous base and a sugar. Nucleotides have one or more additional phosphate groups, while nucleosides do not have any phosphate groups. This difference in structure impacts their functions in various biological processes, such as energy metabolism and the formation of nucleic acids.