nucleic acids 7.3 translation. recap video  http://www.youtube.com/watch?v=nhm 4uuvhpqm...

Download Nucleic Acids 7.3 Translation. Recap video  http://www.youtube.com/watch?v=nHM 4UUVHPQM http://www.youtube.com/watch?v=nHM 4UUVHPQM

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  • Slide 1
  • Nucleic Acids 7.3 Translation
  • Slide 2
  • Recap video http://www.youtube.com/watch?v=nHM 4UUVHPQM http://www.youtube.com/watch?v=nHM 4UUVHPQM
  • Slide 3
  • The Structure of the Ribosome Proteins and RNA molecules (rRNA) 2 sub-units (large and small) 3 binding sites for tRNA on the surface: E = exit site P = peptidyl site A = aminoacyl site 2 tRNA molecules can bind at the same time to the ribosome Binding site for the mRNA on the surface
  • Slide 4
  • The Structure of the Ribosome Protein database http://www.rcsb.org/pdb/home/home.do http://www.rcsb.org/pdb/home/home.do
  • Slide 5
  • Structure of tRNA Loops: sections that become double stranded by base pairing Base sequence CCA forms a site for attaching amino acid Anti-codon: triplet of bases Part of a loop of 7 unpaired bases
  • Slide 6
  • tRNA activating enzymes http://www.youtube.com/watch?v=KThCr1XdUGw http://www.youtube.com/watch?v=KThCr1XdUGw
  • Slide 7
  • Initiation of Translation To begin translation: An mRNA molecule binds to the small ribosomal subunit at the mRNA binding site An initiator tRNA carrying Methionine (MET) binds to the start codon AUG in the P-site The large ribosomal subunit binds to the small one
  • Slide 8
  • Initiation of Translation The next codon signals another tRNA to bind in the A-site A peptide bond is formed between the amino acids in the P and A sites
  • Slide 9
  • Elongation Following initiation The ribosome translocates 3 bases along the mRNA Moving the tRNA in the P-site to the E-site This tRNA is set free A new tRNA with the correct anticodon binds to the next codon in the A-site This series of steps repeats
  • Slide 10
  • Slide 11
  • Termination of Translation The process continues until a stop codon is reached The polypeptide is released The components disassemble Note: direction of movement from 5 to 3
  • Slide 12
  • What does 5 to 3mean?
  • Slide 13
  • Free Ribosomes Free ribosomes synthesize proteins for use primarily within the cell
  • Slide 14
  • Bound Ribosomes Bound ribosomes synthesize proteins primarily for secretion or for use in lysosomes
  • Slide 15
  • Free vs Bound Ribosomes Proteins perform specific functions. They must be sorted to go to the correct location. Whether a ribosome is free in the cytosol or bound to the ER depends on a signal sequence in the polypeptide The signal sequence is at the beginning of the polypeptide
  • Slide 16
  • Free vs Bound Ribosomes As the signal sequence is made it becomes bound to a signal recognition protein Translation stops until the ribosome attaches to a receptor on the ER Translation begins again, with the polypeptide moving into the lumen of the ER.
  • Slide 17
  • Translation and Transcription in Eukaryotes vs Prokaryotes Cellular function is compartmentalized No compartmentalization Modifications of mRNA after transcription before exiting nucleus No modifications Delay between transcription and translation No delay
  • Slide 18
  • Polysomes Polysomes are multiple ribosomes attached to a single mRNA molecule. Strings of polysomes attached to DNA molecule in a prokaryote
  • Slide 19
  • Polysomes In prokaryotes, multiple polysomes are visible associated with one gene. In eukaryotes, polysomes occur on the cytoplasm and next to the ER. Multiple ribosomes translating a single mRNA molecule with the cytoplasm. The polypeptides are longer the closer to the end of the mRNA.

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