protein synthesis

• What is protein synthesis?

  the mechanism in cells whereby:

  • the DNA template is transcribed into a mRNA molecule in the nucleus
  • the mRNA base sequence is then translated into an amino acid sequence in association with tRNA on ribosomes in the cytoplasm
• Process of Transcription

  the production of mRNA from DNA2) only one chain of DNA acts as a template2) the enzyme RNA polymerase moves along the3) free RNA nucleotides align themselves opposite complementary DNA bases4) RNA polymerase joins together mRNA nucleotides and makes short strands of pre-mRNA until it comes to a terminator sequence5) sections of pre-mRNA are spliced together to remove intron sequences and join exon sequences to form mRNA

  1. DNA helicase breaks the hydrogen bonds between bases, causing DNA to unwind and expose bases
• in which organisms does splicing occur ?

  eukaryotes

  • in prokaryotes transcription results directly into mRNA as most don't include introns
• Process of Translation

  the production of polypeptides from the sequence of codons carried by mRNA2) a tRNA (carrying an amino acid) with a complementary anticodon moves to ribosome and pairs with the first mRNA codon3) the ribosome moves along the mRNA, pairing a complementary tRNA to the mRNA4) energy released from ATP is used to form a polypeptide bond between amino acids5) when the ribosome reaches a stop codon, the polypeptide is complete and the RNAs are released and the ribosome can be reused

  1. mRNA moves from the nucleus through a nuclear pore to the cytoplasm and associates with ribosome which moves to the start codon on mRNA