You are here: Gene to Function
> RNA Structure
Structure of RNA
Table of Contents
- The Components of RNA and a few principles
- RNA: a few facts
- What's in a name
- To go further
RiboNucleic Acids consist of:
- Ribose (a pentose = sugar with 5 carbons)
- Phosphoric Acid
- Organic (nitrogenous) bases: Purines (Adenine
and Guanine) and Pyrimidines
(Cytosine and Uracil)
An RNA molecule is a linear polymer in which the monomers (nucleotides)
are linked together by means of phosphodiester bridges, or bonds.
These bonds link the 3' carbon in the ribose of one nucleotide to the 5'
carbon in the ribose of the adjacent nucleotide.
This is illustrated in Figure 1.
Figure 1: A segment of a single nucleic acid chain. This is a clickable
Figure 2: model of a molecule of RNA.
It is not a double helix, but in some places, (shaded in green), the positions of the bases are stabilised by hydrogen bonds.
Naming nucleosides and nucleotides.
The combination of a ribose and a base constitutes a
The combination of a phosphate, a ribose and a base constitutes
RNA : a few facts...
|RNA is found in the nucleus, where it is synthesised, and in the cytoplasm,
as messenger RNA, transfer RNA or ribosomal RNA. All these forms of
RNA are involved in the protein synthesis.
The rule A+C=U+G CAN'T BE APPLIED HERE
Most RNA in the cell is single stranded and does not form a double helix.
|Although each RNA molecule has only a single polynucleotide chain,
it is not a smooth linear structure. It has extensive regions of complementary
AU, or GC pairs. Therefore, the molecule folds on itself forming structures
called hairpin loops. In the base paired region, the RNA molecule adopts
a helical structure as in DNA.
What's in a Name
||Ribo: the pentose has an oxygen in position 2. Compare ribose
||Nucleic: these molecules were first found in the nucleus of the cell,
before being found in mitochondria, the chloroplasts of plants, and in the cytoplasm of prokaryotes
||Acid: only two of the three acid groups of the phosphoric acid
are used to form the DNA chain. The third one gives the phosphoribo-backbone an
There is more than one RNA...
- There are three major classes of RNA
- messengerRNA or m RNA: carries the genetic information out of the nucleus
for protein synthesis.
- transferRNA or t RNA: decodes the information.
- ribosomalRNA or r RNA: constitutes 50% of a ribosome, which is
a molecular assembly involved in protein synthesis.
And to go further
A little bit more work
- Do you think this page looks like the page about DNA?
Compare them, and find out the differences.