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PROTEIN SYNTHESIS

Learn about the process of protein synthesis, including transcription and translation, and how DNA functions as the code of life. Understand the structure of DNA and RNA and their roles in determining the structure of proteins.

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PROTEIN SYNTHESIS

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  1. PROTEIN SYNTHESIS

  2. Protein Synthesis • The production (synthesis) of polypeptide chains (proteins) • Two phases:Transcription & Translation

  3. SCI.9-12.B-4.3 - [Indicator] - Explain how DNA functions as the code of life and the blueprint for proteins. • SCI.9-12.B-4.4 - [Indicator] - Summarize the basic processes involved in protein synthesis (including transcription and translation). • H.B.4B.1 Develop and use models to describe how the structure of DNA determines the structure of resulting proteins or RNA molecules that carry out the essential functions of life.

  4. Transcription – mRNA copying DNA, happens in the nucleus and mRNA must be edited or processed before it leaves the nucleus • Translation – when mRNA goes to ribosome and tRNA brings the correct amino acids to the ribosome

  5. Nuclear membrane DNA Transcription Pre-mRNA RNA Processing mRNA Ribosome Translation Protein DNA  RNA ProteinCentral Dogma Eukaryotic Cell

  6. Pathway to Making a Protein DNA mRNA tRNA (ribosomes) Protein

  7. Nucleic Acids

  8. RNA

  9. SCI.9-12.B-4.1 - [Indicator] - Compare DNA and RNA in terms of structure, nucleotides, and base pairs.

  10. How DNA and RNA are alike: • Both made of monomers called nucleotides. • Both had A,Gand C bases

  11. *RNA Differs from DNA 1. RNA has a sugar ribose DNA has a sugar deoxyribose 2. RNA contains the base uracil (U) DNA has thymine (T) 3. RNA molecule is single-stranded DNA is double-stranded

  12. . *Three Types of RNA • Messenger RNA (mRNA)carries genetic information to the ribosomes • Ribosomal RNA (rRNA),along with protein, makes up the ribosomes • Transfer RNA (tRNA)transfers amino acids to the ribosomes where proteins are synthesized

  13. Making a Protein

  14. *Genes & Proteins • Proteins are made of amino acids linked together by peptide bonds • 20 different amino acids exist • Amino acids chains are called polypeptides • Segment of DNA that codes for the amino acid sequence in a protein are called genes

  15. Two Parts of Protein Synthesis • Transcription makes an RNA molecule complementary to a portion of DNA • Translationoccurs when the sequence of bases of mRNA DIRECTS the sequence of amino acids in a polypeptide

  16. SCI.9-12.B-4.3 - [Indicator] - Explain how DNA functions as the code of life and the blueprint for proteins. • SCI.9-12.B-4.4 - [Indicator] - Summarize the basic processes involved in protein synthesis (including transcription and translation). • H.B.4B.1 Develop and use models to describe how the structure of DNA determines the structure of resulting proteins or RNA molecules that carry out the essential functions of life.

  17. *Genetic Code • DNA contains a triplet code • Every three bases on DNA stands for ONE amino acid • Each three-letter unit on mRNA is called a codon • Most amino acids have more than one codon! • There are 20 amino acids with a possible 64 different triplets • The code is nearly universal among living organisms

  18. *What is the enzyme responsible for the production of the mRNA molecule?

  19. *RNA Polymerase • Enzyme found in the nucleus • Separates the two DNA strands by breaking the hydrogen bonds between the bases • Then moves along one of the DNA strands and links RNA nucleotides together

  20. Question: • What would be the complementary RNA strand for the following DNA sequence? DNA 5’-GCGTATG-3’

  21. Answer: • DNA 5’-GCGTATG-3’ • RNA 3’-CGCAUAC-5’

  22. *Processing Pre-mRNA • Also occurs in the nucleus • Pre-mRNA made up of segments called introns & exons • Exons code for proteins, while introns do NOT! • Introns spliced out by splicesome-enzyme and exons re-join • End product is a mature RNA molecule that leaves the nucleus to the cytoplasm

  23. *Messenger RNA (mRNA) • Carries the information for a specific protein • Made up of 500 to 1000 nucleotides long • Sequence of 3 bases called codon • AUG – methionine or start codon • UAA, UAG, or UGA – stop codons

  24. start codon A U G G G C U C C A U C G G C G C A U A A mRNA codon 1 codon 2 codon 3 codon 4 codon 5 codon 6 codon 7 stop codon protein methionine glycine serine isoleucine glycine alanine Primary structure of a protein aa2 aa3 aa4 aa5 aa6 aa1 peptide bonds Messenger RNA (mRNA)

  25. amino acid attachment site methionine amino acid U A C anticodon Transfer RNA (tRNA)

  26. SCI.9-12.B-4.3 - [Indicator] - Explain how DNA functions as the code of life and the blueprint for proteins. • SCI.9-12.B-4.4 - [Indicator] - Summarize the basic processes involved in protein synthesis (including transcription and translation). • H.B.4B.1 Develop and use models to describe how the structure of DNA determines the structure of resulting proteins or RNA molecules that carry out the essential functions of life.

  27. *Ribosomes • Made of a large and small subunit • Composed of rRNA (40%) and proteins (60%) • Have two sites for tRNA attachment --- P and A

  28. Translation • Synthesis of proteins in the cytoplasm • Involves the following: 1. mRNA (codons) 2. tRNA (anticodons) 3. ribosomes 4. amino acids

  29. *Translation • Three steps: 1. initiation: start codon (AUG) 2. elongation: amino acids linked 3. termination: stop codon (UAG, UAA, or UGA). Let’s Make a Protein !

  30. http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120077/micro06.swf::Protein%20Synthesishttp://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120077/micro06.swf::Protein%20Synthesis

  31. http://sciencenetlinks.com/interactives/protein.html

  32. mRNA A U G C U A C U U C G mRNA Codons Join the Ribosome Large subunit P Site A Site Small subunit

  33. aa2 aa1 2-tRNA 1-tRNA G A U U A C Initiation anticodon A U G C U A C U U C G A hydrogen bonds codon mRNA

  34. aa3 3-tRNA G A A Elongation peptide bond aa1 aa2 1-tRNA 2-tRNA anticodon U A C G A U A U G C U A C U U C G A hydrogen bonds codon mRNA

  35. aa3 3-tRNA G A A aa1 peptide bond aa2 1-tRNA U A C (leaves) 2-tRNA G A U A U G C U A C U U C G A mRNA Ribosomes move over one codon

  36. aa4 4-tRNA G C U peptide bonds aa1 aa2 aa3 2-tRNA 3-tRNA G A U G A A A U G C U A C U U C G A A C U mRNA

  37. aa4 4-tRNA G C U peptide bonds aa1 aa2 aa3 2-tRNA G A U (leaves) 3-tRNA G A A A U G C U A C U U C G A A C U mRNA Ribosomes move over one codon

  38. aa5 5-tRNA U G A peptide bonds aa1 aa2 aa4 aa3 3-tRNA 4-tRNA G A A G C U G C U A C U U C G A A C U mRNA

  39. aa5 5-tRNA U G A peptide bonds aa1 aa2 aa3 aa4 3-tRNA G A A 4-tRNA G C U G C U A C U U C G A A C U mRNA Ribosomes move over one codon

  40. aa5 aa4 Termination aa199 aa200 aa3 primary structure of a protein aa2 aa1 terminator or stop codon 200-tRNA A C U C A U G U U U A G mRNA

  41. aa5 aa4 aa3 aa2 aa199 aa1 aa200 *End Product –The Protein! • The end products of protein synthesis is a primary structure of a protein • A sequence of amino acid bonded together by peptide bonds

  42. http://scetv.pbslearningmedia.org/resource/tdc02.sci.life.gen.proteinsynth/from-dna-to-protein/http://scetv.pbslearningmedia.org/resource/tdc02.sci.life.gen.proteinsynth/from-dna-to-protein/

  43. SCI.9-12.B-4.3 - [Indicator] - Explain how DNA functions as the code of life and the blueprint for proteins. • SCI.9-12.B-4.4 - [Indicator] - Summarize the basic processes involved in protein synthesis (including transcription and translation). • H.B.4B.1 Develop and use models to describe how the structure of DNA determines the structure of resulting proteins or RNA molecules that carry out the essential functions of life.

  44. *Types of Mutations • Point mutation – one DNA bases changes. Sometimes this mistake is corrected by an enzyme. Types: a. insertion – where a base is added b. deletion – where a base is lost c. substitution – where a base is changed

  45. Wild type A A G G G G A U U U C U A A U mRNA 5 3 Lys Protein Met Phe Gly Stop Amino end Carboxyl end Base-pair substitution No effect on amino acid sequence U instead of C A U G A A G U U U G G U U A A Lys Met Phe Gly Stop Missense A instead of G A A U G A A G U U U A G U U A Lys Met Phe Ser Stop Nonsense U instead of A G A A G G U U G A A U U U U C Met Stop Substitution

  46. Wild-type hemoglobin DNA Mutant hemoglobin DNA In the DNA, the mutant template strand has an A where the wild-type template has a T. 3 5 3 5 T T C A T C mRNA mRNA The mutant mRNA has a U instead of an A in one codon. G A A U A G 5 3 5 3 Normal hemoglobin Sickle-cell hemoglobin The mutant (sickle-cell) hemoglobin has a valine (Val) instead of a glutamic acid (Glu). Val Glu • *The change of a single nucleotide in the DNA’s template strand • Leads to the production of an abnormal protein Figure 17.23

  47. http://www.texomashomepage.com/health/healthcast/from-bench-to-bedside-hemophiliahttp://www.texomashomepage.com/health/healthcast/from-bench-to-bedside-hemophilia

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