What is the difference between a nucleoside and a nucleotide?

The question asks for the difference between nucleosides and nucleotides. Let's break down the components: A nucleoside* consists of a nitrogenous base (like adenine, guanine, cytosine, thymine, or uracil) covalently bonded to a pentose sugar (either ribose or deoxyribose). A nucleotide* consists of a nucleoside with one or more phosphate groups attached to the sugar. Now let's evaluate the given options: "only nucleotides have nitrogenous bases": This is incorrect. Both nucleosides and nucleotides contain nitrogenous bases. "a phosphate group is found in nucleotides but not in nucleosides": This is correct. The presence of a phosphate group is the key difference that distinguishes a nucleotide from a nucleoside. "nucleotides have the pentose sugar ribose while nucleosides have the pentose sugar deoxyribose": This is incorrect. Both nucleosides and nucleotides can contain either ribose (in RNA) or deoxyribose (in DNA). The type of sugar depends on the nucleic acid, not on whether it's a nucleoside or nucleotide. "in nucleosides the monomers are joined by phosphodiester bonds; in nucleotides the monomers are joined by hydrogen bonds": This is incorrect. Nucleotides* are joined by phosphodiester bonds to form nucleic acid polymers (DNA or RNA). Hydrogen bonds form between complementary bases in a DNA double helix, not between monomers of nucleosides or nucleotides. "nucleosides are the monomers of DNA; nucleotides are the monomers of RNA": This is incorrect. Nucleotides* are the monomers of both DNA and RNA. The correct option is: a phosphate group is found in nucleotides but not in nucleosides. Last free one today — make it count tomorrow, or type /upgrade for unlimited.