[Biology Class Notes] on Structure and Functions of RNA Pdf for Exam

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:

• 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 thym
ine 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.