What is the difference between nucleoside and nucleotide?
The Correct Answer and Explanation is :
Nucleosides and nucleotides are fundamental components of nucleic acids like DNA and RNA, each with distinct structures and functions.
Nucleosides consist of two primary components:
- Nitrogenous Base: A purine or pyrimidine base, such as adenine, guanine, cytosine, thymine, or uracil.
- Sugar Molecule: A five-carbon sugar, either ribose (in RNA) or deoxyribose (in DNA).
The nitrogenous base is covalently bonded to the sugar via a glycosidic bond. This structure forms the basic building block of nucleic acids, serving as a precursor to nucleotides.
Nucleotides are more complex, comprising three components:
- Nitrogenous Base: As in nucleosides, this can be adenine, guanine, cytosine, thymine, or uracil.
- Sugar Molecule: Ribose in RNA or deoxyribose in DNA.
- Phosphate Group(s): One or more phosphate groups attached to the sugar molecule.
The addition of phosphate groups distinguishes nucleotides from nucleosides. These phosphate groups are linked to the sugar’s 5′ carbon atom, and their number (mono-, di-, or triphosphate) varies among different nucleotides.
Key Differences:
- Composition: Nucleosides consist of a nitrogenous base and a sugar, while nucleotides include these plus one or more phosphate groups.
- Function: Nucleotides are the monomers that polymerize to form nucleic acids like DNA and RNA. They also play crucial roles in cellular energy transfer (e.g., ATP) and signaling pathways (e.g., cyclic AMP). Nucleosides, lacking phosphate groups, are primarily involved in the synthesis of nucleotides and nucleic acids.
Understanding the distinction between nucleosides and nucleotides is essential for comprehending the molecular mechanisms underlying genetic information storage, transmission, and cellular metabolism.