1. DNA, genes + protein synthesis

• "Describe how mRNA is produced in the nucleus of a cell"

  • enzyme DNA helicase breaks hydrogen bonds between complementary DNA base pairs
  • DNA double helix unzips and unwinds exposing DNA nucleotide bases - one of these strands acts as a template
  • free RNA nucleotides are attracted to complementary exposed DNA bases
  • RNA polymerase joins RNA nucleotides together
  • Pre-mRNA is spliced to remove introns forming mRNA
• "how do 2 amino acids differ from one another?"

  • they have different R groups
•  use figure 1, 2 and your own knowledge of enzyme action to explain why the arrows point in opposite directions

  • enzymes are a specific shape for a substrate meaning only a substrate will bind
  • the DNA strands are anti-parallel this means the nucleotides are different shapes on each side
  • this means the nucleotide with the complementary shape will bind to DNA polymerase
• Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation.

  • tRNA molecule with a specific amino acid
  • binds using its anticodon to a complementary codon on the mRNA
  • amino acid join by condensation to form peptide bond