Importance of Biochemistry

RNA definition and examples?

RNA structure and functions

RNA definition and examples?

RNA definition :

RNA definition,short for Ribonucleic Acid, is a complex compound with high molecular weight that is involved in protein synthesis inside the cell, and replaces DNA – deoxyribonucleic acid – as a carrier of genetic information or genes in some viruses.

 Composition of RNA:
RNA is made of ribose nucleotides – nitrogenous bases sticking to a ribose sugar – linked together by phosphodiester bonds, forming chains of various lengths.
The nitrogenous bases that make up RNA are: adenine, guanine, and cytosine, and uracil, which takes the place of thymine in DNA. The ribose sugar that makes up RNA is a cyclic compound made up of five carbonates and one oxygen atom.
The presence of a reactive hydroxyl group bound to the second carbon atom in the ribose sugar molecule makes it susceptible to hydrolysis, there is no such chemical weakness in DNA – it does not contain DNA On the hydroxyl group. 
This is what made DNA evolve to become the main carrier of genetic information in most organisms. The structure of RNA was first described by RW Holley in 1965.

RNA structure:

RNA definition structure and function
RNA structure and function


RNA exists in the form of a single strand of biopolymers, but the self-complementary form of RNA connects its parts together with the folding of the ribonucleotides to form complex fittings made of protrusions and spirals.

The three dimensional shape of Ribonucleic acid:

The three-dimensional shape of ribonucleic acid is very important for its stability and function, which gives the ribonucleic sugar and nitrogenous bases the ability to modify in many forms through cellular enzymes that add chemical groups (such as the methyl group).

These modifications allow the formation of chemical bonds between non-contiguous regions in the RNA, and lead to the formation of twists in the DNA chain, these twists are very important in the task of stabilizing the structure of RNA.

Molecules that are poorly modifiable and unstable are more prone to destruction, for example any prototype tRNA that does not contain a methyl group (tRNAiMet);

It is in the 58th position of the chain that it is unstable and thus becomes ineffective. This ineffective chain will then be destroyed by the specialized cellular quality control system, the vector RNA.


RNA can form bonds with molecules known as ribonucleoproteins (RNPs). It turns out that the DNA aspect of at least one of the RNPs performs catalytic functions. A function that was once thought to be specific to proteins only.

RNA types and functions:

There are many types of RNA, of which three are well known to us:

1.Messenger RNA (mRNA),

2.Transporter RNA (tRNA),

3.Ribosomal RNA (rRNA),

In all living organisms, in addition to these types there are other types of RNA performs vital reactions – as enzymes do – and others have complex functions to regulate intracellular tasks, and because DNA enters many regulatory functions, and to provide it in large quantities; It plays important roles in many cell functions and an important role in many human diseases.

1.Messenger RNA(mRNA):

The messenger RNA in the process of making proteins carries the genetic code from the DNA in the nucleus to the ribosomes, which is the region of protein synthesis in the cytoplasm of the cell (Translation-).

2.Ribosomal RNA(rRNA)

Ribosomes consist of ribosomal RNA and proteins. The parts of ribosomal proteins are encoded and carried on board the ribosomal RNA and made inside the nucleus,

3.Transporter RNA(tRNA):

When they are complete, they are transferred from inside the nucleus to the cytoplasm, as it is an important part in the translation process. Because it is in the process of reading this code carried on board the messenger RNA.

Ribonucleic acid (ribonucleic acid) RNA The transporter ribonucleic acid transmits information within a living cell via messenger RNA protein messenger genes
The transporter ribonucleic acid


A consecutive set of three nitrogen bases in the messenger RNA is dedicated to adding a specific amino acid in the chain that will later form a specific type of protein, while molecules of the carrier RNA – sometimes called soluble or activated RNA – contain less than 100 nucleotides carry the chosen amino acid into the ribosomes, then bind to form the protein.

In addition to messenger RNA, transporter RNA and ribosomal RNA, the larger group of RNAs can be divided into coded RNA (cRNA) and non-coding RNA (ncRNA).


There are two different types of ncRNA accumulating housekeeping-ncRNA such as carrier RNA, messenger RNA, and organization-ncRNA.

Regulatory which can be divided based on size into long ncRNA, containing more than 200 nucleotides, small ncRNA and less than 200 nucleotide, small ncRNA is divided into micro RNA (miRNA, snoRNA small nuclear RNA), small nuclear RNA (snRNA), nested small RNA (siRNA), nested-Piwi RNA (piRNA).

Micro-RNA is of particular interest. It is made up of 22 nucleotides and functions in the regulation of genes in most eukaryotes. It can silence genes (stopping the process of gene expression) by binding to the messenger RNA and stopping the translation process; Thus it inhibits the production of functional proteins.

MicroRNAs role:

Several microRNAs play an important role in cancer and many other diseases. For example, the microRNAs responsible for inhibiting the growth of tumors and those responsible for initiating the growth of tumors can regulate unique target genes; Thus, tumors are able to grow and develop.

Among the important functions of the so-called Piwi RNA, which is made of 26 to 31 nucleotides and is present in most animals: regulation of the appearance of the flip genes; It prevents their appearance in sex cells (sperm and eggs).


Most PiRNA is complementary to different types of transposons and can stop these genes with pinpoint precision. Circular RNA (circRNA) is unique.

The end of terminus 5 ‘is linked to the end of terminus 3’, thus forming a closed knot. This node is formed by a group of genes that encode proteins, and some of them may act as a template for making other proteins, as happens in the case of RNA.

It can also bind to microRNAs, acting like a sponge and preventing it from binding to its targets. In addition, circular RNA plays an important role in regulating the transcription and segmentation of the genes that make up circular RNA.

RNA in diseases:

Important relationships have been discovered between RNA and many diseases of humanity. For example, and as previously stated: Some microRNAs have the ability to regulate genes responsible for the onset of cancer in a way that could allow this disease to develop.

In addition, it has been shown that the irregularity of the RNA destruction process is linked to the emergence of several neurodegenerative diseases such as Alzheimer’s disease.

In the case of other types of RNA, it is possible for the transporter RNA to bind to a group of proteins called caspases, as they play an important role in the apoptosis process, inhibiting their work by binding to these proteins.

Cells escape from the programmed death process is One of the most important pillars of cancer, there is also a group of non-coding RNA known as fragments derived from vector RNA.

It is expected to be related to cancer. The emergence of modern techniques such as decoding RNA sequences has led to the knowledge of new types of genetic texts for cancer.

Example MALATI:

(metastasis associated lung adenocarcinoma transcript) 1 – The presence of a high proportion of this text in tissue cells is a strong indication of the spread of cancer cells.

A group of RNA contains a repeating sequence that isolates a group of RNA-binding proteins. The isolation leads to the formation of aggregations in nerve tissue.

ALS(Amyotonic lateral sclerosis):

These clusters play a role in many neurological diseases such as amyotonic lateral sclerosis (ALS) and myotonic dystrophy, He emphasized that functional loss, dysregulation, or a mutation in this group of RNA-binding proteins is linked to many human diseases.

It is expected that more relationships between RNA and human diseases will be discovered. Increased knowledge of DNA and its functions is supported by increased development in the processes of decoding RNA genomic sequences and efforts made in scans of both RNA and RNA binding proteins in therapeutic processes; All of this would facilitate these discoveries.

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