Translation

Cards (17)

  • Translation
    1. Ribosome decodes mRNA created during transcription
    2. Ribosome turns mRNA code into a polypeptide
  • Codon
    A chain of 3 nucleotides that encodes for a specific amino acid
  • There are 20 different amino acids
  • The genetic code is redundant
  • Start codon
    AUG encodes for methionine (Met), the only start codon
  • Stop codons
    • UAA
    • UAG
    • UGA
  • Translating mRNA into protein
    1. Read codons one at a time
    2. Assemble amino acids in the right sequence
    3. Occurs in the 5' to 3' direction of the mRNA
    4. With the help of transfer RNA (tRNA)
  • tRNA
    Folded RNA molecule with an anticodon loop complementary to the mRNA codon, carries a specific amino acid
  • The 3rd nucleotide in the anticodon is often less important than the first two
  • The 3rd nucleotide is in the "wobble" position, allowing fewer tRNA to be needed
  • Phases of Translation
    1. Initiation
    2. Elongation
    3. Termination
  • Ribosome
    • Complex of proteins and RNA
    • Has 3 binding sites for tRNA
  • Initiation
    1. tRNA carrying met attaches to small ribosomal subunit
    2. Complex binds to mRNA cap and travels to start codon
    3. Binds to large ribosomal subunit to begin translation
  • Elongation
    1. tRNA matching codon binds to A site
  • Termination
    1. Stop codon enters A site
    2. Release factor binds and facilitates hydrolysis to free polypeptide chain
    3. Complex separates to be reused
  • Post-translational modifications
    • Amino acids may be removed
    • Polypeptide can be divided into pieces
    • Multiple polypeptides can join to form larger proteins
    • Polypeptides fold into 3D structure with chaperone proteins
    • Specific amino acid sequences can target proteins to organelles
  • Polysome
    Multiple ribosomes reading the same mRNA, allowing more protein to be made simultaneously