RNA- Properties, Structure, Types and Functions
Ribonucleic acid (RNA) is a polymer of nucleotides, essential for various biological functions including coding, decoding, regulation, and expression of genes.
Properties of RNA
RNA Is a single-stranded helix
The strand as a 5′ end with a phosphate group and a 3′ end with a hydroxyl group
It is composed of ribonucleotides
The ribonucleotides are linked together by 3′ → 5′ phosphodiester bonds
The nitrogenous bases that compose the ribonucleotides include adenine, cytosine, uracil, and guanine
The bases that DNA consists of include adenine, thymine, cytosine, and guanine
In RNA, uracil replaces thymine. Though these poth pair with adenine
Most RNA molecules are single-stranded, however an RNA molecule may have regions that can form complementary base pairing where the RNA strand loops back on itself. If this so happens, the RNA will have double sided region(s)
rRNA and tRNA substantially exhibit this secondary structure, as do some mRNAs
Types of RNA
In both prokaryotes and eukaryotes, there are 3 main types of RNA
rRNA - ribosomal RNA
tRNA - transfer RNA
mRNA - messenger RNA
mRNA - Messenger RNA
mRNA carries the genetic code that is copied form the DNA during transcription in what we call codons. Codons are triplets of nucleotides. mRNA carries codons which are segments of genetic code derived from DNA during the process of transcription
As mentioned before, mRNA contains a 5′ cap and a 3′ tail
The 5′ end is capped with a guanosine triphosphate nucleotide, which helps in mRNA recognition during translation and/or protein synthesis
The 3′ end has a poly A tail, which prevents enzymatic degradation of mRNA
mRNA takes the genetic code from DNA and uses that to synthesize proteins
mRNA carries genetic information from the nucleus of a cell toits cytoplasm
rRNA - Ribosomal RNA
Different strands of rRNA present in the ribosomes in either small sized rRNA or large sized rRNA, which denote their presence in the small and large subunits of the ribosome
rRNA combines with proteins in the cytoplasm to form ribosomes, which act as the site of protein synthesis
rRNA also contains enzymes needed for the process of protein synthesis
During translation, rRNA travels along the mRNA molecule and facilitates the assembly of amino acids to form a polypeptide chain. rRNA is also able to bind to tRNA and other molecules that are crucial for protein synthesis
tRNA - Transfer RNA
The main function of tRNA is during translation; tRNA transfers amino acids during protein synthesis
Each of the 20 amino acids has a specific tRNA that binds with it and transfers it to the growing polypeptide chain formed during translation
tRNA also acts as an adapter in the translation of the genetic sequence involving mRNA translating into proteins
tRNA has a clover leaf structure stabilized by strong hydrogen bonds between the nucleotides. The hydrogen bonds form 3 structural loops
The 3′ end serves as the amino acid attachment site
The center loop encompasses the anticodon. The anticodon is a 3-base nucleotide sequence that binds to the mRNA codon
This interaction between codon and anticodon specifies the next amino acid to be added during protein synthesis
Transfer RNA brings amino acids to the ribosome. Each amino acid corresponds to one of the codons on the rRNA. The amino acids can then be joined together to make polypeptides and proteins
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