Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation, and expression of genes. RNA and DNA are nucleic acids, and, along with lipids, proteins and carbohydrates, constitute the four major macromolecules essential for all known forms of life. Like DNA, RNA is assembled as a chain of nucleotides, but unlike DNA it is more often found in nature as a single-strand folded onto itself, rather than a paired double-strand. Cellular organisms use messenger RNA (mRNA) to convey genetic information (using the letters G, U, A, and C to denote the nitrogenous bases guanine, uracil, adenine, and cytosine) that directs synthesis of specific proteins. Many viruses encode their genetic information using an RNA genome. 

Some RNA molecules play an active role within cells by catalyzing biological reactions, controlling gene expression, or sensing and communicating responses to cellular signals. One of these active processes is protein synthesis, a universal function where RNA molecules direct the assembly of proteins on ribosomes. This process uses transfer RNA (tRNA) molecules to deliver amino acids to the ribosome, where ribosomal RNA (rRNA) then links amino acids together to form proteins. 

Like DNA, most biologically active RNAs, including mRNA, tRNA, rRNA, snRNAs, and other non-coding RNAs, contain self-complementary sequences that allow parts of the RNA to fold and pair with itself to form double helices. Analysis of these RNAs has revealed that they are highly structured. Unlike DNA, their structures do not consist of long double helices, but rather collections of short helices packed together into structures akin to proteins. In this fashion, RNAs can achieve chemical catalysis (like enzymes). For instance, determination of the structure of the ribosome—an enzyme that catalyzes peptide bond formation—revealed that its active site is composed entirely of RNA.
What is the article about?
What is it similar to?
What is it similar to?
What does it do?
What do they actively do?
How is it different from DNA?
What shape are they?
Are they like enzymes?
How?
What kind of acids are they?
RNA
RNA
DNA
DNA
unknown
unknown
codes, decodes, regulates, and expresses genes
coding, decoding, regulation, and expression of genes
catalyze biological reactions, control gene expression, sense and communicate responses to cellular signals
catalyzing biological reactions, controlling gene expression, or sensing and communicating responses to cellular signals
single-strand rather than double-strand
 single-strand folded onto itself, rather than a paired double-strand
collections of short helices packed together into structures akin to proteins
 collections of short helices packed together into structures akin to proteins
yes
 In this fashion, RNAs can achieve chemical catalysis (like enzymes)
they can achieve chemical catalysis
RNAs can achieve chemical catalysis
nucleic acids
nucleic acids