Nucleobase vs. Nucleoside

Nucleobasenoun

(biochemistry) The base of a nucleic acid, such as thymine, uracil, adenine, cytosine and guanine.

Nucleobase

Nucleobases, also known as nitrogenous bases or often simply bases, are nitrogen-containing biological compounds that form nucleosides, which, in turn, are components of nucleotides, with all of these monomers constituting the basic building blocks of nucleic acids. The ability of nucleobases to form base pairs and to stack one upon another leads directly to long-chain helical structures such as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA).

Nucleosidenoun

(biochemistry) an organic molecule in which a nitrogenous heterocyclic base (or nucleobase), which can be either a double-ringed purine or a single-ringed pyrimidine, is covalently attached to a five-carbon pentose sugar (deoxyribose in DNA or ribose in RNA). When the phosphate group is covalently attached to the pentose sugar, it forms a nucleotide.

Nucleosidenoun

A type of molecule found in all living organisms, present mostly in chemically combined form as a component of nucleic acids, and also in smaller amounts in free form, consisting of a pentose sugar bound to a purine or pyrimidine base; two types of nucleoside, ribonucleoside and deoxyribonucleoside, are present. The most common bases present in nucleosides are adenine, cytosine, uracil, guanine, and thymine, and to a lesser extent hypoxanthine and other bases are found. The most commmon ribonucleosides composed from these bases are called adenosine, cytidine, uridine, and guanosine. The forms esterified with orthophosphoric at the 5-position of the pentose are called nucleotides. The nucleotides form the monomer units which are combined into DNA and RNA, which carry the genetic information required for reproduction in all known organisms.

Nucleosidenoun

a glycoside formed by partial hydrolysis of a nucleic acid

Nucleoside

Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group. A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a five-carbon sugar (ribose or 2'-deoxyribose) whereas a nucleotide is composed of a nucleobase, a five-carbon sugar, and one or more phosphate groups.