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Synthesis of Proteins or the Formation of the Conga Line


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Differences and similarities between DNA and RNA. Synthesis of proteins

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Synthesis of Proteins or the Formation of the Conga Line

  1. 1. * C,H,O,N,S Amino acids • Meat, fish, chicken, egg white,milk, cheese, pork, peas, beans and cereals • Soluble in WATER • Needed for CELLS,ANTIBODIES, ENZYMES; used for ENERGY if all the stores have run out (17kj/g) • We eat food to make us! by re assembling it
  2. 2. Ok! But what happens to the Amino Acids that are needed? It’s like cooking pizza! ! DNA MrNA Amino Acids Ribosomes Proteins
  3. 3. • We go from to torNA Proteins nucleus cytoplasm Transcription Translation
  4. 4. information flows in one direction when genes are expressed The Central Dogma of molecular biology:
  5. 5. • Nucleic acids made up of chains of nucleotides • Nucleotides consist of: – A nitrogenous base – A sugar (ribose) – A phosphate • Two types of nucleic acids in cells: – Deoxyribonucleic acid (DNA) – Ribonucleic acid (RNA)
  6. 6. Nucleic acids have primary and secondary structures – DNA • Double- stranded helix • Carries genetic information • Transmitted from parents to children in the sexual gamets – RNA • 3 kinds (mRNA, tRNA, rRNA) • All single strands
  7. 7. • The different bases in the nucleotides which make up DNA and RNA are: – Adenine – Guanine – Cytosine – Thymine (DNA only) – Uracil (RNA only) • Chemical structure only allows bases to bind with specific other bases due to chemical structure DNA RNA Adenine Uracil** Thymine* Adenine Guanine Cytosine Cytosine Guanine
  8. 8. - Located in 23 pairs of chromosomes in nucleus of cell – Genetic code universal in all organisms – Mitochondrial DNA slightly different – DNA has two functions: • Replication - reproduces itself when cell divides • Information transmission – via protein synthesis
  9. 9. Each parent strand serves as a template for a new strand and the two new DNA strands each have one old and one new strand Parent strands New / daughter strand : combination of DNA & histones
  10. 10. • To start, an enzyme breaks the hydrogen bonds that hold base- pairs together. • This process “unzips” the DNA molecule. • Other enzymes find and correctly match free- floating nucleotides to the two sides of the now open DNA molecule. • This process continues until the entire molecule has been replicated. Growth Growth Replication fork DNA polymerase New strand Original strand DNA polymerase Nitrogenous bases Replication fork Original strand New strand
  11. 11. : carries genetic information from DNA in nucleus to cytoplasm where proteins synthesize carries amino acids from amino acid pool to mRNA joins with ribosomal proteins in ribosome where amino acids joined to form protein primary structure.
  12. 12. making mRNA from DNA base sequence in mRNA is translated into an amino acid sequence in a protein Transcription Translation RNA polymerase catalyses synthesis of RNA
  13. 13. formed on a single strand of DNA by the process of transcription in the nucleus Transcription requires an enzyme known as RNA polymerase
  14. 14. Base sequence of mRNA is complementary to that of DNA CODON: is a set of three adjacent nucleotides, also called triplet, in DNA or mRNA that designates a specific amino acid to be incorporated into a polypeptide Each polypeptide contains a combination of any or all of the 20 different amino acids The properties of proteins are determined by the order in which different amino acids are joined together
  15. 15. Promoters serve as punctuation marks, telling the RNA polymerase: where to start which strand of DNA to read the direction to take from the start 1 2 3
  16. 16. Function: carry amino acids present in the cytoplasm to the ribosome
  17. 17. Occur in the nucleus 1. modification of both ends of pre-mRNA 2. removal of introns
  18. 18. ribosome
  19. 19. Besides the cytoplasm, name TWO other regions inside the eukaryotic cell that contain ribosomes. Chloroplast Mitochondrion Some ribosomes in chloroplast & mitochondria are even smaller than those of prokaryotes.
  20. 20. • Mitochondria contain their own DNA and protein synthesizing machinery • Mitochondrial genetic code slightly different – Codon-anticodon interactions simplified • Synthesise only small number of proteins – Most mitochondrial proteins coded for in nucleus and transported into mitochondria
  21. 21. • Information in mRNA translated into primary sequence of a protein in 4 steps: – ACTIVATION – INITIATION – ELONGATION – TERMINATION
  22. 22. A U G G G C U U AAA G C A G U G C A C G U U This is a molecule of messenger RNA. It was made in the nucleus by transcription from a DNA molecule. mRNA molecule codon
  23. 23. A U G G G C U U AAA G C A G U G C A C G U U A ribosome on the rough endoplasmic reticulum attaches to the mRNA molecule. ribosome
  24. 24. A U G G G C U U AAA G C A G U G C A C G U U It brings an amino acid to the first three bases (codon) on the mRNA. Amino acid tRNA molecule anticodon U A C A transfer RNA molecule arrives. The three unpaired bases (anticodon) on the tRNA link up with the codon. Start codon is AUG; first amino acid is always methionine, which may be removed after translation.
  25. 25. A U G G G C U U AAA G C A G U G C A C G U U Another tRNA molecule comes into place, bringing a second amino acid. U A C Its anticodon links up with the second codon on the mRNA.
  26. 26. A U G G G C U U AAA G C A G U G C A C G U U A peptide bond forms between the two amino acids. Peptide bond
  27. 27. A U G G G C U U AAA G C A G U G C A C G U U The first tRNA molecule releases its amino acid and moves off into the cytoplasm.
  28. 28. A U G G G C U U AAA G C A G U G C A C G U U The ribosome moves along the mRNA to the next codon.
  29. 29. A U G G G C U U AAA G C A G U G C A C G U U Another tRNA molecule brings the next amino acid into place.
  30. 30. A U G G G C U U AAA G C A G U G C A C G U U A peptide bond joins the second and third amino acids to form a polypeptide chain.
  31. 31. A U G G G C U U AAA G C A G U G C A C G U U The polypeptide chain gets longer. The process continues. This continues until a termination (stop) codon is reached. The polypeptide is then complete.
  32. 32. Termination: translation ends when a stop codon [ UAA, UAG, UGA] enters the A site.
  33. 33. Enzymes degrade mRNA The ribosome subunits dissociate.
  34. 34. A ribosome can combine with any mRNA and all tRNAs. What is the significance of this?
  35. 35. • The end product of protein synthesis is a primary structure of a protein. • A sequence of amino acid bonded together by peptide bonds. aa1 aa2 aa3 aa4 aa5 aa200 aa199
  36. 36. methionine glycine serine isoleucine glycine alanine stop codon protein A U G G G C U C C A U C G G C G C A U A AmRNA start codon Primary structure of a protein aa1 aa2 aa3 aa4 aa5 aa6 peptide bonds codon 2 codon 3 codon 4 codon 5 codon 6 codon 7codon 1
  37. 37. A protein may be moved to an organelle or out of the cell
  38. 38. List four materials (shown here) that are required for translation to occur: 1. Amino acids 2. mRNA 3. tRNA 4. ribosome
  39. 39. What happens if a mutation occurs at a GENE? Protein produced may fail to function = genetic disease e.g. Sickle-Cell Anaemia: Mutation at a SINGLE base
  40. 40. Haemoglobin – has more than 300 amino acids A single base change in the gene for haemoglobin results in a lethal condition
  41. 41. Wrong sequence of amino acids = Wrong folding = NON FUNCTIONAL PROTEIN
  42. 42. Transcription • Information transcribed from DNA into RNA – mRNA carries information for protein structure, but other RNA molecules formed in same way • RNA polymerase binds to promoter nucleotide sequence at point near gene to be expressed • DNA helix unwinds • RNA nucleotides assemble along one DNA strand (sense strand) in complementary sequence to order of bases on DNA beginning at start codon (AUG - methionine) • Transcription of DNA sense strand ends at terminator nucleotide sequence • mRNA moves to ribosome • DNA helix rewinds From: Tortora, GJ & Grabowski SR (2000) Principles of Anatomy and Physiology (9th Ed). New York: John Wiley & Sons. P88.
  43. 43. • DNA structure by Hank Green (you can add subtittles!!) • Protein Synthesis by Hank Green (you can add subtittles too!!) Funny videos: AMEBA SISTERS . Differences between DNA and RNA: • Protein Synthesis: