RNA

RNA stands for Ribo Nucleic Acid. Ribo: the pentose sugar with 5 carbons and oxygen in position 2, Nucleic: these molecules were first found in the nucleus of the cell, Acid: only two of the three acid groups of the phosphoric acid are used to form the DNA chain. The third one gives the phosphoribo-backbone an acidic property.RNA is structurally similar to DNA. Both are sugar-phosphate polymers and both have nitrogen bases attached to the sugars of the backbone except few differences. An RNA molecule is a linear polymer in which the nucleotides are linked together by means of phosphodiester bonds. These bonds link the 3' carbon in the ribose of one nucleotide to the 5' carbon in the ribose of the adjacent nucleotide. Thus RNA consists of:
1.Ribose (a pentose = sugar with 5 carbons)
2.Phosphoric Acid
3.Organic (nitrogenous) bases: Purines (Adenine and Guanine) and Pyrimidines (Cytosine and Uracil)
RNA is found in the nucleus and cytoplasm. Some RNAs are involved in the protein synthesis while some other RNAs are important in some catalytic steps. The rule A+C=U+G (Chargaff rule) can’t be applied there. Double standed RNA exists in some viruses only are generally similar to A-DNA (present is few viruses).mainly RNA can be divided into 3 categories-
1.Ribosomal RNAs (rRNA) -exist in the cytoplasm of a cell in structures called ribosomes. Each ribosome is a complex consisting of about 60% ribosomal RNA and 40% protein.
2.Messenger RNAs (mRNA) - take information from DNA in the cell nucleus and carry it to the ribosome.
3.Transfer RNAs (tRNA) - deliver amino acids one by one to protein chains growing at ribosome.