Question

RNA molecules are of three types which are based on their different functions. These are:
A: messenger RNA, translational RNA, structural RNA
B: cytosine RNA, nucleoside RNA, nucleotide RNA
C: messenger RNA, ribosomal RNA, transfer RNA
D: primary RNA, secondary RNA, tertiary RNA

Answer 1

RNA molecules i.e. ribonucleic acid are structurally quite the same as that of DNA. The difference is that DNA molecules are specifically long as well as double stranded whereas RNA molecules are shorter as well as single stranded. Though RNA molecules are engaged with many roles in cells, the major role is regulation and synthesis of protein (translation).

Complete step by step answer:
The three types of RNA molecules that are directly engaged in synthesis of protein are messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA). The function of each type of RNA molecules have been discussed below:
Messenger RNA (mRNA): mRNA, coding RNA, carries the message (genetic code) from DNA in a format or order that can easily be perceived to synthesize proteins. This coding sequence of mRNA molecules identifies the sequence of amino acids of protein produced. After getting transcribed from DNA, mRNA comes in contact with ribosomes as well as other cellular machinery to promote protein (it encodes) synthesis during translation.
Ribosomal RNA (rRNA): rRNA is the major catalytic portion of the ribosomes. rRNA allows proper positioning of mRNA, tRNA, as well as ribosomes. rRNA also possesses an enzymatic activity (i.e. peptidyl transferase) where it catalyzes the peptide bonds formation during protein synthesis between the two aligned amino acids.
Transfer RNA (tRNA): tRNA is a small RNA molecule having around 80 nucleotides. It is responsible to carry the correct amino acid sequence to the protein synthesis site in the ribosome. It is considered to be the base pairing between the mRNA and tRNA that inserts the correct amino acid in the synthesized polypeptide chain.

Note:
Any mutations that are encountered in the rRNA or tRNA result in global problems for cells since both RNA molecules are crucial for protein synthesis.
Numerous clinically important viruses contain RNA, instead of DNA, which holds the viral genetic information. Apart from this, RNA also plays a significant role in regulating the cellular processes which include cell division, differentiation, growth and even cell aging or death.