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Transfer RNA—the Anticodons

المؤلف:  John E. Hall, PhD

المصدر:  Guyton and Hall Textbook of Medical Physiology

الجزء والصفحة:  13th Edition , p32

2026-11-08

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Another type of RNA that plays an essential role in protein synthesis is called transfer RNA (tRNA) because it transfers amino acid molecules to protein molecules as the protein is being synthesized. Each type of tRNA combines specifically with 1 of the 20 amino acids that are to be incorporated into proteins. The tRNA then acts as a carrier to transport its specific type of amino acid to the ribosomes, where protein molecules are forming. In the ribosomes, each specific type of tRNA recognizes a particular codon on the mRNA (described later) and thereby delivers the appropriate amino acid to the appropriate place in the chain of the newly forming protein molecule.

Transfer RNA, which contains only about 80 nucleotides, is a relatively small molecule in comparison with mRNA. It is a folded chain of nucleotides with a cloverleaf appearance similar to that shown in Figure 1. At one end of the molecule there is always an adenylic acid to which the transported amino acid attaches at a hydroxyl group of the ribose in the adenylic acid.

Fig1. A messenger RNA strand is moving through two ribosomes. As each codon passes through, an amino acid is added to  the growing protein chain, which is shown in the right-hand ribosome. The transfer RNA molecule transports each specific amino acid  to the newly forming protein. 

loosely by hydrogen bonding with the codon bases of the mRNA. In this way, the respective amino acids are lined up one after another along the mRNA chain, thus establishing the appropriate sequence of amino acids in the newly forming protein molecule.