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section 5, chapter 4


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protein synthesis

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section 5, chapter 4

  1. 1. Section 5, Chapter 4 Transcription & Translation
  2. 2. There are several kinds of RNA Messenger RNA (mRNA): Conveys genetic information from DNA to the ribosomes Transfer RNA (tRNA): Transfers amino acids to the ribosomes during translation. Ribosomal RNA (rRNA): Provides structure and enzyme activity for ribosomes 4
  3. 3. Messenger RNA (mRNA): Delivers genetic information from the DNA inside the nucleus to the cytoplasm mRNA is formed beside a strand of DNA RNA nucleotides are complementary to DNA nucleotides with one exception – no thymine in RNA; replaced with uracil) mRNA DNA S P A U T A G C C G G C P Direction of “reading” code S S P P S S P P S S P P S S P S Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. P
  4. 4. 5. mRNA undergoes further processing & leaves the nucleus
  5. 5. A Codon is the 3 letter nucleotide sequence of mRNA that encodes for 1 amino acid. AUG is the first codon in protein synthesis, so it’s it’s called the start codon
  6. 6. Protein Synthesis The codon sequence of mRNA determines the amino acid sequence of a protein. Figure 4.23
  7. 7. The start codon marks the site at which translation into protein sequence begins, and the stop codon marks the site at which translation ends. amino acid
  8. 8. tRNA Clover-leaf shape RNA with 2 important regions Amino acid binding site Anticodon
  9. 9. Ribosomes Small particle of protein & ribosomal RNA (rRNA) Ribosomes have 2 subunits Large subunit holds tRNA & amino acids Small subunit binds to mRNA Small subunit has 2 binding sites for adjacent mRNA codons Ribosomes link amino acids by peptide bonds
  10. 10. Ribosomes Peptide bond forming large subunit anticodons small subunit Binding sites with codons
  11. 11. 1. mRNA binds to the small subunit of a Ribosome. 2. The ribosome ‘reads’ the mRNA sequence 3. tRNA brings amino acids to the ribosomes, aligning their anticodons with mRNA codons 4. The Ribosome links the amino acids together 5. Polypeptide chain lengthens
  12. 12. Anchors polypeptide.
  13. 13. tRNA released
  14. 14. Figure 4.23 overview of protein synthesis TRANSCRIPTION
  15. 15. Once translation is complete chaperone proteins fold the protein into its configuration post-translational modification enzymes may further modify proteins after translation phosphorylation – adding a phosphate to the protein glycosylation – adding a sugar to the protein End of Chapter 4