Unit B7 8 Protein Synthesis


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Unit B7 8 Protein Synthesis

  1. 1. Unit B7 - 8: Cell Biology (Protein Synthesis) Authored by Michelle Choma© Students who have fully met the prescribed learning outcomes (PLO’s) are able to:  B7. Demonstrate an understanding of the process of protein synthesis.  identify the roles of DNA, mRNA, tRNA, and ribosomes in the process of transcription and translation, including initiation, elongation, and termination.
  2. 2. Unit B7 Continued  determine the sequence of amino acids coded for by a specific DNA sequence (genetic code), given a table of mRNA codons.  identify the complementary nature of the mRNA codon and the tRNA anti-codon.
  3. 3. B8. Explain how mutations in DNA affect protein synthesis.  give examples of two environmental mutagens that can cause mutations in humans.  use examples to explain how mutations in DNA change the sequence of amino acids in a polypeptide chain, and as a result may lead to genetic disorders.
  4. 4. Web Sites & Links for Protein Synthesis  http://www.coolschool.ca/lor/BI12/unit6/U06L00.htm (Unit 06)  ☺Scroll to Lesson 01 – Lesson 04 (‘U06L01 – L04’)  http://highered.mcgraw- hill.com/sites/0072421975/student_view0/chapter2 4/  (Mader’s Student Edition Website Support for Chapter 24; Animations, quizzes, flashcards, Thinking Scientifically etc.)  http://sps.k12.ar.us/massengale/pwpt_biology.htm  Power point presentation on Protein Synthesis  http://sps.k12.ar.us/massengale/nucleic_acids_.htm  (Nucleic acids & protein synthesis, animations)
  5. 5. Some more….  http:// www.phschool.com/science/biology_place/index.html  Check out the ‘The Biology Place’; Click on link to ‘BioCoach’ activities on Transcription & Translation.  Fabulous Reviews, Animations, Practice & Self-quiz etc.  http://www.scilinks.org/retrieve.asp  (Sign up on this site. Great links on protein synthesis: Link code, cbn-4123)  http://www.phschool.com/webcodes10/index.cfm?wcp refix=cbe&wcsuffix=4123&fuseaction=home.gotoWeb Code&x=11&y=18  (Great animation on protein synthesis)
  6. 6. And some more….  http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.html  http://www.pbs.org/wgbh/aso/tryit/dna/index.html#  (Protein Synthesis activity & animation)  http://nobelprize.org/educational_games/medicine/dna/intro.htm l (Review & Animations of protein synthesis)  http://www.wisc-online.com/objects/index_tj.asp?objid=AP1302  http://www.eurekacityschools.org/ehs/riggsw/Transcription.ppt (Powerpoint)  http://learn.genetics.utah.edu/ (Animation)  Terrific activities. Check out the Genetics Reference Series and click on link to ‘The Basics and Beyond’. Follow directions for Transcribing & Translating a Gene.
  7. 7. And more!  http:// www.pbs.org/wgbh/aso/tryit/dna/shockwave  www.lewport.wnyric.org/jwanamaker/ani mations/Protein%20Synthesis%20- %20long.html  http://www.wisc- online.com/objects/index_tj.asp?objid=A P1302
  8. 8. And more links  http://waynesword.palomar.edu/lmexer3.htm  ☺Check out the many topics & related articles in the ‘Table of Contents’  http://www.estrellamountain.edu/faculty/farabee/biobk/BioBook PROTSYn.html  http://distance.stcc.edu/BIOL102/Lectures/lesson10/makeprot. htm  http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookgl ossN.html#nucleic acids  http://workbench.concord.org/web_content/unitV/sickle_cell_wo rksheet_s.html (a model-based activity to make a sickle-cell mutation)  http://workbench.concord.org/web_content/unitV/muta_wksht_s .html (a model-based activity to make substitution & deletion mutations)  http://www.quizmebc.ca/
  9. 9. Introduction  Protein synthesis is the manufacture/synthesis of proteins.  Occurs in the nucleus and cytoplasm.  The genetic codes for specific proteins are located on the DNA, e.g. codes for keratin, collagen, Hb, polymerase, amylase, pepsin etc.
  10. 10. Introduction Continued  The triplet genetic codes on DNA are called codons. This is a sequence of three DNA bases.  The site for protein synthesis occurs on the ribosomes (rRNA and protein) in the cytoplasm.
  11. 11. Protein synthesis: divided into 2 processes: (A) Transcription: copying the codons for a protein from a segment of the DNA strand to make mRNA (messenger RNA); requires 2 enzymes (helicase, RNA polymerase). Includes steps of initiation, elongation and termination.
  12. 12. Second Process (B) Translation: translate the sequence of codons for the protein on the mRNA to build a protein at the ribosome; tRNA assists in this process. Includes steps of initiation, elongation and termination.
  13. 13. B7– Roles of the Molecules Involved in Protein Synthesis (a) DNA  Contains the information/genetic code/triplet codes/codons for the synthesis of proteins, e.g. TCG, ATG, ATT.  Provides a template for mRNA to be produced.
  14. 14. Let’s draw this together!!
  15. 15. (b) mRNA  Carries the coded message from the nucleus to the cytoplasm, e.g. codons UAA, CGC, AGU  Sets the order of amino acids for protein synthesis by the sequence of codons. (Codon = 3 bases/ nucleotides in a DNA or RNA sequence which specify a single amino acid.)
  16. 16. (c) Ribosomes  Provides a site for mRNA and tRNA to join together by complementary base pairing.  Site for protein synthesis (i.e. translation) where it translates mRNA and allows amino acids to bond (peptide bond).
  17. 17. Note:  rRNA & protein make up the small and large subunits of ribosomes. The small subunit contains the binding site for mRNA and the large subunit contains 2 binding sites for tRNA ~ amino acid and a dehydration synthesis site!
  18. 18. Remember this!!??
  19. 19. (d) tRNA  Carries the specific amino acid to the ribosome where its anticodon complementary base pairs with the mRNA codon, e.g. mRNA codon- UUA; anticodon- AAU.
  20. 20. (e) Amino acids  These are the monomers of proteins and are picked up by tRNA in the cytoplasm, i.e. tRNA~ amino acids.
  21. 21. Note:  mRNA Codon Table (see below) tells what 3 bases on mRNA code for each amino acid (64 combinations of 3 bases)  Methionine (AUG) on mRNA is called the ‘START codon’ because it triggers the linking of amino acids  UAA, UGA, & UAG on mRNA signal ribosomes to stop linking amino acids together
  22. 22. mRNA tRNA Amino DNA Codon  Anticodon  Acid  Codon     GCU       TAC                 AUU        UUU        TCA                 UCU     CTT          
  23. 23. B7– Steps of Protein Synthesis  Key words: initiation, elongation, termination, transcription, translation, elongation, DNA, mRNA, tRNA, ribosome, amino acid, triplet code/codons, template, H-bonds, complementary pairing, RNA polymerase, anticodon, peptide bond, polypeptides, dehydration synthesis.
  24. 24. Animations  http://highered.mcgraw-hill.com/sites/0072421975/stude  http://www.pbs.org/wgbh/aso/tryit/dna/index.html#  (Protein Synthesis activity & animation)  http://www.lewport.wnyric.org/jwanamaker/animation s/Protein%20Synthesis%20-%20long.html  http://www.wisc- online.com/objects/index_tj.asp?objid=AP1302  http://learn.genetics.utah.edu/  http://www.eurekacityschools.org/ehs/riggsw/Transc ription.ppt
  25. 25. 1. Transcription (involves steps of initiation, elongation & termination)  Location: nucleus  Product: mRNA  Requires 2 enzymes: helicase and RNA polymerase.
  26. 26. Here we go….. (a) DNA containing genetic code for protein is in triplet codes. (b) Initiation: RNA polymerase initiates transcription by locating and binding to the beginning of a gene/code (i.e. the promoter region).
  27. 27. (c) Elongation: -Helicase unwinds, unzips DNA, breaks H-bonds and provides a template for mRNA formation.  RNA polymerase travels down the template and complementary base pairs RNA nucleotides with DNA codons forming a mRNA,  e.g. DNA – CAT; mRNA – GUA.  RNA polymerase joins adjacent nucleotides to mRNA, forming the S-P-S backbone.
  28. 28. (d) Termination: -RNA polymerase reaches termination sequence at end of gene/code and STOPS mRNA synthesis. RNA polymerase releases the mRNA and detaches from the DNA.  mRNA exits nucleus through its pores and enters the cytoplasm; DNA rejoins.
  29. 29. Note:  mRNA carries a sequence of codons (linear order of three RNA bases complementary to DNA triplet code) to the ribosome…  One is a “STOP” codon, e.g. UAA, UAG and UGA and a “START” codon, e.g. AUG (Methionine).
  30. 30. 2. Translation (involves steps of initiation, elongation and termination)  Location: cytoplasm at the ribosome  Product: protein/polypeptide
  31. 31. Translation (a) tRNAs in the cytoplasm attach the correct amino acid to one end (aided by enzymes). (b) Initiation: tRNA~methionine binds to small subunit and this binds to the mRNA. tRNA anticodon (UAC) complementary pairs with mRNA “ START” codon (AUG). Large subunit binds to the small subunit assembling a ribosome.
  32. 32. Translation continued (c) Elongation: -Another tRNA (i.e. tRNA~amino acid) with its anticodon complementary base pairs with mRNA codon on the ribosome. (It has 2 binding sites for incoming tRNA~aa)  Ribosomes move along one codon to receive the next incoming tRNA~aa.
  33. 33.  Amino acid undergoes dehydration synthesis and forms a peptide bond.  “Empty” or outgoing tRNA will bond with another amino acid in the cytoplasm, i.e. tRNA~aa.
  34. 34. (d) Termination: Synthesis of polypeptide until a “STOP” codon on mRNA (UAA, UAG, UGA). Termination of protein synthesis and the polypeptide chain and mRNA are released from the ribosome. Ribosome subunits separate.
  35. 35.  Ribosomes can synthesize 5-15 peptide bonds/sec!  Most proteins are 100-200 aa long & takes less than a minute to be synthesized!
  36. 36.  http://nobelprize.org/educational_games/medicin (click on animation icon)  http://highered.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535: :535::/sites/dl/free/0072437316/120077/mi cro06.swf::Protein%20Synthesis (Great animation)  http://sps.k12.ar.us/massengale/proteinsynth esis%20ppt.ppt (Nice power points 1 & 2 on Transcrip/lation)  http://sps.k12.ar.us/massengale/protein%20s ynthesis2%20ppt.ppt
  37. 37. B7– Problems Using the “Table of mRNA codons”  Use the following table to answer questions 1 – 7.  Note: most of the amino acids are coded with 2, 3 or even 4 different codons. Of these 64 codons, 61 are used to program the 20 amino acids. Three of the 64 codons are used as signals to start or stop the program.
  38. 38. Links  http://learn.genetics.utah.edu/ Visit the Genetics Reference Series and click on link to ‘The Basics and Beyond’. Follow the directions for synthesis of a protein.
  39. 39. Ok Let’s Try it Out! 1.) What are the RNA triplet codes for Lysine? Leucine?  using the mRNA table, the codons for Lysine are AAA or AAG.  using the mRNA table, the codons for Leucine are CUU, CUC, CUA, CUG, UUA and UUG.
  40. 40.  2.) What is the DNA triplet code for Tryptophan? mRNA = UGG (from table) DNA = ACC.  3.) What are the mRNA triplet codons for “STOP”? using the mRNA table, the codons are UAA, UAG and UGA.
  41. 41. 4.) The anticodon on a tRNA is GCU. Determine the name of the amino acid and its triplet codon. tRNA anticodon GCU would complementary base pair with mRNA CGA at the ribosome. using the table, the amino acid code for CGA is Arginine.
  42. 42. 5.) DNA contains the following genetic code: TACAAGATT. Determine the amino acid sequence. DNA = TAC|AAG|ATT mRNA = AUG|UUC|UAA = methionine-phenylalanine-stop (from table).