Types of RNA Molecules

Ribonucleic acids are similar in overall composition to DNA, but cells contain up to eight times as much RNA as DNA. RNA is found in large amounts in the cytoplasm and in a smaller amount in the nucleus; within the cytoplasm it is mainly located in the ribosomes, and within the nucleus it is mainly located in the nucleolus.

RNA molecules are classified, according to their structure and function, into three major types: ribosomal RNA (rRNA), messenger RNA (mRNA) and transfer RNA (tRNA).

rRNA is found mainly in the cytoplasm, as part of the ribosomes, which are themselves composed of about 60% RNA and 40% protein. Ribosomes are the physical sites at which protein synthesis takes place.

tRNA molecules have the lowest molecular weight of all the nucleic acids, consisting of just 73-94 nucleotides arranged in a single chain. The function of tRNA is to carry amino acids to the sites of protein synthesis on the ribosomes. …