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Protein Synthesis

Protein Synthesis. Part 2: Translation. Translation. Assembling a protein using the instructions carried by mRNA Where? Ribosomes!. Nucleus. Messenger RNA is transcribed in the nucleus. mRNA. Proteins. Proteins are chains of amino acids (AA) Proteins are also called polypeptide chains

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Protein Synthesis

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  1. Protein Synthesis Part 2: Translation

  2. Translation • Assembling a protein using the instructions carried by mRNA • Where? Ribosomes! Nucleus Messenger RNA is transcribed in the nucleus. mRNA

  3. Proteins • Proteins are chains ofamino acids(AA) • Proteins are also calledpolypeptide chains • There are 20 amino acids. Examples: • Methionine (Met) • Serine (Ser) • Valine (Val) • Alanine (Ala) • Different proteins have different AA sequences: Met – Val – Ala – Cys – Val - Ser

  4. The Genetic Code • Codon= three consecutive nucleotides on mRNA • Each codon specifies an AA: • AUG -> Methionine (Met) • UCA -> Serine (Ser) • The sequence of codons on mRNA determine the sequence of AA’s in the protein

  5. The Genetic Code mRNA: UCGCACGGU UCG-CAC-GGU Ser – His - Gly

  6. Types of RNA • mRNA– messenger RNA • Carries instructions from nucleus to ribosome for protein synthesis • rRNA– ribosomal RNA • What ribosomes are made of (made in the nucleolus) • tRNA– transfer RNA • Carry AA’s to ribosome as proteins are assembled

  7. tRNA • Carries an AA on one end • Has ananticodonon the other end • Anticodon is complementary to the codon on mRNA • What is the anticodon for UCG? • What is the anticodon for CAC? • What is the anticodon for GGU?

  8. Nucleus Messenger RNA is transcribed in the nucleus. mRNA Lysine Phenylalanine tRNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. Methionine Ribosome Start codon mRNA Translation

  9. Animation The Polypeptide “Assembly Line” The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. Growing polypeptide chain Ribosome tRNA Lysine tRNA mRNA Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. mRNA Ribosome Translation direction

  10. A Real Life Example! Firefly Animation

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