núkleótíðinni

A nucleotide is the basic building block of nucleic acids, DNA and RNA. Each nucleotide consists of three components: a nitrogenous base, a five-carbon sugar (ribose in RNA and deoxyribose in DNA), and one or more phosphate groups. The nitrogenous bases are adenine (A), guanine (G), cytosine (C), thymine (T) in DNA, and uracil (U) in RNA. Adenine and guanine are purines, while cytosine, thymine, and uracil are pyrimidines.

The sugar and phosphate groups form the backbone of the DNA or RNA strand, with the nitrogenous bases projecting inwards. These bases pair up in a specific way: adenine always pairs with thymine (or uracil in RNA), and guanine always pairs with cytosine. This complementary base pairing is crucial for DNA replication and transcription.

Nucleotides also play vital roles in cellular energy metabolism, acting as energy currency in the form of adenosine triphosphate (ATP). Furthermore, they are components of coenzymes like NAD+ and FAD, which are essential for many biochemical reactions. The sequence of nucleotides in DNA carries the genetic information that determines the characteristics of an organism.