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Structure and Functions of RNA

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What is RNA?

RNA, an abbreviation of ribonucleic acid, is a complex high molecular weight compound that functions in the synthesis of cellular proteins and replaces DNA ( deoxyribonucleic acid) as a carrier of genetic codes in some viruses. RNA consists of ribose nucleotides (nitrogenous bases bound to a ribose sugar) connected by phosphodiester bonds, forming variable length chains. adenine, guanine, cytosine, and uracil are the nitrogen bases in RNA, which replace thymine in DNA. RNA, ribonucleic acid is a type of nucleic acid that contributes to protein synthesis.


RNA is a ribonucleic acid that helps with protein synthesis in our bodies. The production of new cells in the human body is responsible for this nucleic acid. Usually, it is obtained from the molecule of DNA. RNA is similar to DNA, the only difference being that it has a single strand, unlike the DNA that has two strands and consists of a single ribose sugar molecule within it. Thus the name is Ribonucleic acid. RNA is also called an enzyme, as it helps with chemical reactions in the body.


Basic Structure of RNA

The ribonucleic acid has all the components the same as that of the DNA with only 2 main differences within it. RNA has the same bases of nitrogen called adenine, guanine, cytosine as the DNA, except for the thymine that is replaced by uracil. Adenine and uracil are regarded as the major RNA building blocks and both form base pairs with the help of 2 hydrogen bonds.RNA resembles a hairpin structure and like the nucleotides in DNA, nucleotides are formed in this ribonucleic material(RNA). Nucleosides are nothing but groups of phosphates which also sometimes help in the production of nucleotides in DNA.


Functions of RNA

Ribonucleic Acid – RNA, which consists mainly of nucleic acids, is involved in a variety of cell functions and is found in all living organisms including bacteria, viruses, plants, and animals. These nucleic acid functions in cell organelles as structural molecules, and are also involved in biochemical reaction catalysis. The various types of RNA participate in a separate cellular cycle. The primary functions of RNA:

  • Facilitate the translation of DNA into proteins

  • Functions as an adapter molecule in  protein synthesis

  • Serves as a messenger between the DNA and the ribosomes.

  • They are the carrier of genetic information in all living cells

  • Promotes the ribosomes to choose the right amino acid which is required in the building up of new proteins in the body. 


History of RNA

Nucleic acids were first discovered in 1868 by Friedrich Miescher who named the substance 'nuclein' because it was located in the nucleus and this led to RNA being discovered. The key milestone in RNA history is outlined below;

Some of the highlights of RNA molecules are given below,

  • Due to its sensitivity to alkaline – OH group on the ribose, RNA was distinctly different from DNA

  • The key energy source and building blocks for RNA were ATP and GTP.

  • The three bases common to RNA and DNA were adenine, cytosine, and guanine while Uracil is present in the RNA instead of thymine.


RNA Types

There are different types of RNA out of which the human body is most well-known and most commonly studied:

  • TRNA-RNA transfer

  • The transfer RNA is responsible for selecting the correct protein or the amino acids that the body requires to help the ribosomes in turn. It is at the endpoints of any amino acid. This is also called soluble RNA and constitutes a connection between messenger RNA and amino acid

  • rRNA-Ribosomal RNA

  • The rRNA is the ribosome portion and is located within a cell's cytoplasm, where ribosomes are found. In all living organisms, the Ribosomal RNA is mainly involved in the synthesis and translation of mRNA into proteins. The rRNA is composed primarily of cellular RNA and is the most prevalent RNA in the cells of all living organisms

  • mRNA – Messenger RNA

As the name itself says, this RNA is responsible for bringing the genetic material to the ribosomes and insists on what kind of protein the body needs. It is therefore called messenger RNA. This m-RNA is usually involved in the transcription process, or during the process of protein synthesis.


RNA Functions in Protein Synthesis

Cells access the information stored in DNA by producing RNA, which directs the creation of proteins via the translation process. Proteins within cells perform a variety of roles, including cellular structure formation and acting as enzyme catalysts for cellular chemical reactions that give cells their distinct properties. Messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA are the three main forms of RNA that are directly involved in protein production (tRNA).


In 1961, French scientists François Jacob and Jacques Monod proposed the existence of messenger RNA, a link between DNA and its protein products.


Shortly after,16 pieces of evidence were acquired to confirm their claim, demonstrating that information from DNA is conveyed to the ribosome for protein synthesis via mRNA. If DNA is the whole library of cellular information, mRNA is a photocopy of specific information required at a certain point in time.


The message from the DNA is carried by the mRNA, which governs all cellular activity in a cell. If a cell requires the synthesis of a specific protein, the gene for that product is "turned on," and the mRNA is generated via the transcription process (see RNA Transcription). During the translation process, the mRNA interacts with ribosomes and other cellular machinery (Figure 10.22) to direct the production of the protein it encodes (see Protein Synthesis). Because mRNA is relatively unstable and short-lived in the cell, particularly in bacterial cells, proteins are only produced when they are required.


Fun Facts

RNA is an acronym for ribonucleic acid, which is a nucleic acid. There are many different kinds now known. 


RNA is physically distinct from DNA: DNA contains two intercoiled strands, while RNA contains just one strand. RNA also contains different DNA bases. These are the following bases -

  1. Adenine

  2. Guanine 

  3. Cytosine 

  4. Uracil


Adenine also binds to uracil, and guanine also binds to cytosine. Therefore, we state that adenine is complementary to uracil and that guanine is complementary to cytosine. The first three bases are also found in DNA, but uracil replaces thymine as a supplement to adenine.


RNA also contains ribose rather than deoxyribose present in DNA. These differences mean that RNA is chemically more reactive than DNA. This makes it the most suitable molecule to take part in cell reactions. 


RNA is the carrier of genetic information for certain viruses, particularly retroviruses such as the HIV virus. That is the only exception to the general rule that DNA is a hereditary substance.

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FAQs on Structure and Functions of RNA

1. What are the different types of RNA?

For the translation of genetic information (DNA) into proteins, three different types of RNA are identified, present in prokaryotic and eukaryotic organisms.

  • The genetic information is carried by messenger RNA ( mRNA)

  • RNA transfer (tRNA) acts as the physical connection between mRNA and proteins

  • Ribosomal RNA ( rRNA) occurs on protein-synthesizing ribosomes

2. Explain the functions of RNA?

Analogous rRNAs from different species fold into a similar three-dimensional structure that contains numerous stem-loops and protein, mRNA, and tRNA binding sites. As a ribosome travels along an mRNA a region of the rRNA molecule in each ribosome sequentially binds the amino-activated ends of incoming tRNAs and is likely to catalyze the formation of peptide bonds. Thus it synthesizes a protein.

3.  What role does capping play in RNA processing in eukaryotes?

RNA is an example of a nucleic acid that contains the 5-carbon sugar ribose. This differs from DNA in that DNA molecules include a 5-carbon sugar known as 2'-deoxyribose. The RNA molecule is involved in a variety of biological processes throughout the body. RNA capping is one of these mechanisms.


Capping happens at the 5'-end of the RNA molecule and is required for mature RNA production. Capping is a necessary step for RNA molecules before they can be translated. There are various degradative enzymes in the cell, and capping RNA molecules protects them from degradation as they travel to the cell's cytoplasm for translation. The translation is the process through which proteins or peptide molecules are created in the cell using RNA molecules.

4. Explain the meanings of mRNA and rRNA.

Messenger RNA, or mRNA, is a single-stranded molecule that plays a role in protein production. Ribosomes are organelles that transform mRNA codons into their matching amino acids. Transcription generates mRNA in the nucleus, which is then exported to the cytoplasm. The corresponding sequence of one strand of DNA is found in mRNA.


Ribosomal RNA, or rRNA, is the primary structural component of ribosomes. rRNA accounts for 50 to 60 percent of the overall weight of a ribosome. Ribosomes are required in the cell for protein synthesis. The majority of the RNA in a cell is rRNA.

5. What are the two most significant distinctions between DNA and RNA in terms of molecular weight (i.e., the relative number of base pairs) and chemical composition?

DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are both nucleic acids, although they differ in several ways.

DNA and RNA have different molecular weights.


DNAs are huge molecules with double strands organized helically; DNA normally has over 1000 base pairs. RNAs, on the other hand, are made up of a single nucleotide strand with a maximum base pair count of 1000. As a result, DNA has a larger molecular weight than RNA.


The chemical composition of DNA and RNA differs.

The sugar component of DNA molecules is deoxyribose, and the two pyrimidine bases found in its strands are cytosine and thymine. In contrast, the sugar component of the RNA molecule is ribose, and the pyrimidine bases are uracil and cytosine.

6. Describe how the anatomy of polynucleotides imparts polarity or directionality on DNA and RNA molecules.

The unique biochemical arrangement of a certain strand of genomic DNA is referred to as directionality in cellular biology. This indicates the attribute of maintaining direction as well as maintaining a trajectory.


Polarity refers to the orientation of such nucleic acid threads. The polynucleotide component is divided into several types of bases that are chemically linked to produce a string. The molecular polarization of the strand is dictated by how such polynucleotide monomers have been progressively coupled. Individual polynucleotide chains have opposite polarity and are perpendicular to one another. A phosphate group interaction joins neighboring sequences inside a continuous thread formed by the carbon atoms 3' and 5'. The anatomical or structural elements that help define directionality are that the 5'-phosphate site usually connects with the growing string's 3' hydroxyl site.

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