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PROTEIN SYNTHESIS

PROTEIN SYNTHESIS. Protein Synthesis. The production (synthesis) of polypeptide chains (proteins) Two phases: Transcription & Translation. SCI.9-12.B-4.3 - [Indicator] - Explain how DNA functions as the code of life and the blueprint for 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

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