Ribonucleic acid

Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and DNA are nucleic acids, and, along with lipids, proteins and carbohydrates, constitute the four major macromolecules essential for all known forms of life. Like DNA, RNA is assembled as a chain of nucleotides, but unlike DNA it is more often found in nature as a single-strand folded onto itself, rather than a paired double-strand.

Structure

RNA is made from nucleotides, each of which is made up of a base (adenine, cytosine, guanine, and uracil), a ribose sugar, and a phosphate. A base, sugar, and phosphate are known as a nucleotide. These nucleotides form a chain, which naturally folds into complex shapes.

Types of RNA

There are many types of RNA, but the three most well-known and most commonly studied are mRNA, tRNA, and rRNA, which are involved in protein synthesis.

Messenger RNA (mRNA)

Messenger RNA (mRNA) is the RNA that carries information from DNA to the ribosome, the sites of protein synthesis (translation) in the cell.

Transfer RNA (tRNA)

Transfer RNA (tRNA) is a small RNA chain of about 80 nucleotides that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation.

Ribosomal RNA (rRNA)

Ribosomal RNA (rRNA) is the catalytic component of the ribosomes. Eukaryotic ribosomes contain four different rRNA molecules: 18S, 5.8S, 28S and 5S rRNA.

Functions

RNA is transcribed from DNA by enzymes called RNA polymerases and is generally further processed by other enzymes. RNA is central to protein synthesis. Here, a type of RNA called messenger RNA carries information from DNA to structures called ribosomes. These ribosomes are made from proteins and ribosomal RNAs, which come together to form a molecular machine that can read messenger RNAs and translate the information they carry into proteins.

See also

• DNA
• Protein synthesis
• Nucleic acid sequence
• Gene expression

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