Nitrogenous bases refer to the portion of a nucleotide that consists of a ring-structured compound that contains nitrogen. The RNA bases can either be pyrimidines consisting of one ring, or purines, which are double-ringed compounds. Purines adenine (A) and guanine (G) as well as the pyrimidines cytosine (C) and uracil (U) are the RNA bases, while DNA bases are the same, to the exclusion of uracil, which is exchanged with thyamine (T). Nucleotides are joined together, creating a code necessary for directing the processes of protein synthesis in two complex steps — transcription and translation.
Nucleic acids are macromolecules that carry genetic information and define the type of protein synthesized by a cell. There are a couple types of nucleic acids residing within the nucleus of human cells: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA encompasses the genes, which are responsible for storing the instructions for production of every protein type as well as RNA necessary for survival. It is RNA that is used to unite amino acids, forming polypeptides that become proteins when linked together. Proteins are essential for the formation and repair of new tissues, and work as hormones and enzymes that drive many metabolic processes constantly occurring within the body.
The structure of RNA nucleotides includes ribose, which is a type of sugar made up of five carbons, one of the RNA bases, and a phosphate group. Determined by DNA and RNA bases, nucleotides can be linked together with each other in any order, but the sequenced nucleotides transform into a translatable code. In RNA, the base adenine consistently pairs with uracil, and cytosine always pairs with guanine to create a triplet codon like UUU, for example, which is the code for the amino acid phenylalanine. An important distinction to note is that RNA typically comprises a single nucleotide strand, as DNA is made of two that are linked together due to hydrogen bonding and coiled around each other forming what is known as the double-helix.
Molecules of RNA are produced from DNA in a process called transcription, yielding three different varieties — messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA). The mRNA is responsible for moving coded instructions for protein synthesis out of the nucleus into the cell's cytoplasm, a process referred to as translation. Ribosomal RNA is then used to create ribosomes, cell organelles that serve as locations for protein synthesis. Transfer RNA is necessary for transporting the newly-assembled amino acid to become part of a polypeptide chain.