Structures of RNA

• Just like DNA, Ribonucleic acid is a long molecule known as a polynucleotide. Poly refers to many and a nucleotide is the monomer that makes up this polymer
• a single RNA nucleotide consists of 3 parts:

  • a phosphate
  • a pentose sugar called ribose
  • a nitrogenous base
• in order for the polynucleotide RNA to form, the individual nucleotides have to join together during condensation reactions. During these reactions, phosphodiester bonds form between the pentose sugar of one nucleotide and the phosphate of the next nucleotide
• State 3 structural differences between DNA and RNA

  Similarities:

  • Both polynucleotides
  • Nucleotides contain pentose sugar
  • nucleotides can have adenine, cytosine and guanine bases
  • both have phosphodiester bonds between adjacent nucleotides

  Differences:

  • DNA is double stranded. RNA is single stranded
  • DNA nucleotides contain sugar deoxyribose. RNA contains sugar ribose
  • DNA nucleotides have base thymine. RNA have the base Uracil
  • DNA has hydrogen bonds. RNA is single stranded so no bonds
• Transcription


  Transcription takes place inside the nucleus whereas translation occurs at the ribosome in the cytoplasm. As DNA is a double-stranded polynucleotide, it is too big to move out of the buclear envelop through the nuclear pores. Therefore, a single-stranded molecule (RNA) is essential to carry the code to the ribosome to be translated.
• messenger RNA (mRNA)


  During the 1st stage of protein synthesis called transcription, which occurs in the nucleus, RNA nucleotides line up opposite a template strand on DNA by using complimentary base pairing. The enzyme RNA polymerase will move along and catalyse condensation reactions to enable phosphodiester bonds go form between the adjacent RNA nucleotides. The result is a strand of mRNA which can now leave the nucleus via the nuclear pores
• RNA is a single stranded, unstable and relatively short
• mRNA in eukaryotes


  the technical name for the mRNA produced at the end of transcription is actually primary or pre-mRNA. This is because it contains non-coding regions called introns as well as the coding regions called exons. The introns will be removed during splicing and the resulting strand is now called post-transcriptional mRNA
• transcription in prokaryotes


  transcription results directly in the production of mRNA from DNA
• Transfer RNA (tRNA)


  tRNA picks up specific amino acids and brings them down to the ribosome. tRNA has a group of 3 bases called a codon which is found on mRNA. The tRNA uses this anti-codon to bind to the codon and this holds the amino acids in places until they form peptide bonds with an adjacent amino acid when forming the growing polypeptide chain
• Ribosomal RNA (rRNA)


  rRNA is the RNA component of the ribosome. It forms an association with protein to form the ribosome where protein synthesis takes place (translation)
• What is translation


  the process through which information encoded in messenger RNA (mRNA) directs the addition of amino acids during protein synthesis.
• what is transcription


  the process through which information encoded in messenger RNA (mRNA) directs the addition of amino acids during protein synthesis.