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The Structure of RNA – Sugar, Phosphate Group, and Nitrogenous Bases

The structure of RNA consists of nucleotides, which are made of three parts. The sugar group, phosphate group, and nitrogen base constitute the nucleotide structure. Repeating units of nucleotides are linked together to form RNA.

RNA, or ribonucleic acid, contains genetic information that is required for the synthesis of proteins. There are several types of RNA molecules, including mRNA, rRNA, and tRNA. Each has a different role in the production of proteins, but all RNA molecules have the same basic structure.


The structure of a RNA molecule consists of repeating units called nucleotides. The structure of nucleotides consists of three parts. There is a sugar molecule, a phosphate group, and a nitrogen-containing base. Each nucleotide is linked to each other through a phosphodiester bond, which is formed between the phosphate group of one nucleotide and the sugar molecule of the next nucleotide.


In RNA, the sugar molecule is a pentose ring that contains two hydroxyl groups (-OH). This differs from DNA, which consists of a pentose with only one hydroxyl group.


The phosphate group consists of a phosphate atom bound to four oxygen atoms. One of the oxygen atoms of the phosphate group binds to the last carbon of the pentose ring.

Nitrogen Bases – Purines and Pyrimidines

The third component of nucleotides is the nitrogen base. RNA bases include the purines adenine and guanine, and the pyrimidines cytosine, and uracil. The bases are bound to the first carbon of the pentose ring through one of their nitrogen atoms.

Base Pairing and Overall RNA Structure

RNA can exist as a single strand or a double strand. The single stranded RNA molecule consists of a series of nucleotides linked by phosphodiester bonds. The double stranded RNA molecule features phosphodiester linkages, as well as base pairing. Base pairing is the attraction between nitrogen bases as they meet in the center of the double helix structure. Adenine pairs with uracil and guanine pairs with cytosine.


Nelson, David L. Lehninger Principles of Biochemistry 4th ed. W.H. Freeman and Company. 2005

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