Polynucleotide vs. Nucleotide — What's the Difference?

A polynucleotide refers to a long chain composed of many nucleotides linked together by covalent bonds. These chains form the backbone of DNA and RNA, carrying genetic information crucial for biological functions and heredity. A nucleotide, on the other hand, is a molecule made up of three components: a sugar (deoxyribose in DNA and ribose in RNA), a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, guanine in DNA; adenine, uracil, cytosine, guanine in RNA). Nucleotides serve not only as the monomeric units of polynucleotides but also play essential roles in cellular energy transfer and metabolism.

While polynucleotides are integral to the structure and function of nucleic acids, individual nucleotides have broader functions within the cell, including participation in energy transfer as adenosine triphosphate (ATP) and in signaling pathways as cyclic adenosine monophosphate (cAMP). This dual role highlights the versatility and importance of nucleotides beyond their function in polynucleotides.

The formation of polynucleotides from nucleotides involves dehydration synthesis reactions, where the phosphate group of one nucleotide forms a covalent bond with the sugar of another, creating a sugar-phosphate backbone with nitrogenous bases as appendages. This process is fundamental to the replication and expression of genetic information.

While a polynucleotide is a macromolecule critical for storing and transmitting genetic information, nucleotides are versatile molecules that play several key roles in the cell, from serving as building blocks of nucleic acids to participating in energy metabolism and cell signaling.