The Chemical Constitution of RNA

Introduction

RNA is the ribonucleic acid molecule that is composed of polynucleotide chains arranged in a single strand and are folded onto themselves instead of pairing as a double helical strand. RNA is responsible for playing a major role in various functions of the body including the coding, decoding, expression and regulation of genes. RNA is the type of nucleic acid that is essential for living beings, especially in viruses along with carbohydrates, proteins, and lipids and is an important macromolecule. RNA is composed of several chemicals that include sugar, phosphate, nitrogen bases, etc. RNA helps mainly in conveying genetic information and in the synthesis of protein.

Nucleic acid was first discovered from the nuclei of the pus cells by Friedrich Miescher. The nucleic acids are of two types: deoxyribonucleic acids (DNA) and ribonucleic acids (RNA). The discovery of RNA was first done by Freidrich Meischer in 1868 when he discovered nucleic acids. He named RNA ‘nuclein’ earlier as it was found in the nucleus of the cell. Although the structure of DNA and RNA was quite similar there were certain distinctive features that made RNA different from DNA. RNA was found to be more sensitive towards alkali as it consists of OH-group in its ribose sugar structure. It was also revealed that RNA shares three common base pairs with DNA that include adenine, guanine, and cytosine while uracil was placed instead of thymine in RNA. 

Structure of RNA

RNA is the ribonucleotides that are single-stranded and are linked with the help of phosphodiester bonds. The nucleotides are the monomeric unit in the nucleic acid that is composed of three main constituents: – a five-carbon sugar, a nitrogenous base, and phosphoric acid. The sugar and phosphate groups are the repeating units that are combined together and form a sugar-phosphate backbone. The nitrogenous bases have a heterocyclic structure. There are two types of nitrogenous bases that are found; purines and pyrimidines. Adenine and guanine are the two types of purines while cytosine and uracil are the two types of pyrimidines found in RNA.

Phosphate group

The phosphate group is composed of a phosphorus atom that consists of four negatively charged oxygen atoms that are attached to it. 

5-carbon sugar

It is also known as pentose sugar which includes the deoxyribose found in the nucleic acid. They have five carbon atoms along with hydrogen atoms and hydroxyl groups and one oxygen atom. 

In the case of ribose sugar, the hydroxyl groups are attached to the carbon atoms of the second and third numbers. This attachment with the sugar molecule gives RNA instability, thus making it more suitable for the functions of a short period of time. 

Nitrogen base

In nucleic acid, the nitrogen atom acts as a base as it gives electrons to various molecules that result in the formation of new molecules. It can also create a ring structure to bind with carbon, hydrogen, and oxygen molecules.

Ring structures are of two types: purines (double rings), and pyrimidines (single rings). Pyrimidines consist of cytosine,  and uracil while purines consist of adenine and guanine. Purines are larger than pyrimidines, this size difference helps in determining the pairings in the strands of nucleic acids. 

Nucleic acid bonds

The glycosidic and the ester bonds are those bonds that help in holding the sugar, phosphorus, and nitrogen molecules together. The bonds between the first carbon atom of the 5-carbon sugar and the nitrogen atom of a ninth number of the nitrogenous base are called glycosidic bonds. The bond between the fifth carbon atom of the 5-carbon sugar and the phosphate group is called ester bonds.

These bonds hold single nucleotides and also several nucleotides together that form the polynucleotides. These polynucleotide chains will be formed by the bonding of the fifth carbon atom in a 5-carbon sugar and the third carbon atom in the next 5- carbon sugar that results in the formation of the sugar-phosphate backbone. 

In the case of RNA, the linking of the base pairs occurs due to the presence of hydrogen bonds. The pairing of adenine and uracil instead of thymine is done with the help of two hydrogen bonds while the base pairing of cytosine and guanine occurs due to the presence of three hydrogen bonds. Although RNA is a single-stranded molecule all this base pairing in RNA will result in the making of a three-dimensional structure. There are different types of RNAs depending upon their function that are listed below.

Types of RNA 

RNA is also known as ribonucleic acid that consists of a single-stranded structure and is found inside the cell of various life forms. They are mainly of three types: 

(i) Messenger RNA: The most important function of mRNA is that it carries genetic codons (made up of three nucleotides), that result in the coding of the amino acids that results in the synthesis of proteins.  

(ii) Transfer RNA: Their main function is the formation of protein. They act as the intermediate help in the interaction between the protein and the language of the nucleic acid that is found inside the cytoplasm of the living cell. 

(iii) Ribosomal RNA: This RNA is made up of ribosomes whose main function is to synthesize proteins in both the eukaryotes and the prokaryotes. 

Functions of RNA

• The major function of RNA is to synthesize protein with the help of DNA that stores information and creates RNA, this process is called transcription
• Proteins are essential for every living being and help in performing various functions
• The process of synthesis of proteins with the RNA is called translation
• RNA acts as the messenger between the DNA and the ribosomes
• It helps the ribosomes in choosing the correct amino acid for the building of new proteins
• These nucleic acids act as the structure molecules in the cell organelles of an organism
• They are responsible for the catalysis of various biochemical processes and also help in performing several cellular processes
• RNA is also referred to as an enzyme as it helps in performing the various chemical reactions in the body

Conclusion 

RNA is the messenger of biological information that is transferred from one generation to the next. They help in the process of synthesis of proteins in the body which is very essential for the development of body parts. It also carries genetic information in the case of certain viruses where DNA is absent. RNA may be single-stranded, double-stranded, or even circular in shape in the case of different viruses depending upon their need. There are many RNAs that do not code for proteins. About 97% of the transcribed RNA is non-coding in eukaryotes but they can be coded by their own RNA genes and help in the formation of proteins.