RNA Structure (Edexcel IGCSE Biology) : Revision Note

RNA Structure

• Like DNA, the nucleic acid RNA (ribonucleic acid) is a polynucleotide

  • It is made up of many nucleotides linked together in a long chain

• RNA nucleotides contain the nitrogenous bases adenine (A), guanine (G) and cytosine (C)

• Unlike DNA, RNA nucleotides never contain the nitrogenous base thymine (T) – in its place they include the nitrogenous base uracil (U)

• RNA molecules are only made up of one polynucleotide strand (they are single-stranded)

• Each RNA polynucleotide strand is made up of alternating ribose sugars and phosphate groups linked together, with the nitrogenous bases of each nucleotide projecting out sideways from the single-stranded RNA molecule

• Examples of an RNA molecules are:

  • messenger RNA (mRNA) which is the transcript copy of a gene that encodes a specific polypeptide

  • transfer RNA (tRNA) which is involved in protein synthesis

  • ribosomal RNA (rRNA) which forms part of a ribosome

Messenger RNA (mRNA) provides a good example of the structure of RNA