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Protein Synthesis

Protein Synthesis. By: Sophie gollan. In this experiment we modelled the structure of DNA and the processes involved in protein synthesis from the information in the DNA. DNA structure. DNA - a double stranded helix molecule which consists of subunits called nucleotides.

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Protein Synthesis

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  1. Protein Synthesis By: Sophie gollan

  2. In this experiment we modelled the structure of DNA and the processes involved in protein synthesis from the information in the DNA

  3. DNA structure • DNA - a double stranded helix molecule which consists of subunits called nucleotides. • Each nucleotide contains a sugar, a phosphate, and a base. • There are four bases: • adenosine • thymine • cytosine • guanine • Alternate sugar and phosphates form the sides, and the bases are connected to the sugars making “rungs” like a ladder. • The chemical structure of the bases allow them each to pair up with only one other base, thus they form complementary pairs. • The complementary pairs are: • Adenosine and thymine • Cytosine and guanine

  4. Protein synthesis • The information about the number, type and sequence of amino acids, needed to make a protein molecule, is found as a code in DNA. • The code- a sequence of bases. • One gene sequence codes for one polypeptide (a single chain of many amino acids) • A set of 3 bases (a codon) codes for one amino acid of a polypeptide. • A protein is one or more polypeptides.

  5. Equipment • 42 toothpicks • 18 milk bottles cut in half (36 halves) – sugar • 18 raspeberry lollies cut in half- phosphate • 25 jelly beans cut in half (5 of each 5 colours)- bases: • Adenosine- orange • Thymine- purple • Cytosine- pink • Guanine- green • Uracil- blue • 4 jelly snake, aproxx. 6cm long, different colours • A4 white paper representing a cell • Colored paper circle, 6cm diameter- a ribosome • Clean sharp knife • Cutting board • Gloves • Scissors • Marking pen • Heinemann Biology textbook

  6. Transcription • A gene length of DNA unwinds in the nucleus. This is the area containing the information about the protein to be made.

  7. RNA polymerase enzyme moves along the exposed single DNA strand linking complementary RNA nucleotides together to form a mRNA strand. • RNA contains the base uracil where thymine is found in DNA. (uracil replaces thymine) • The ‘start’ codon and the ‘stop’ codon control the length of the mRNA strand

  8. The mRNA strand is then modified so that it only consists of the base sequence that will code for the protein. It removes the non-coding regions, introns, while still in the nucleus by splicing the coding regions, exons, together. • The modified mRNA then moves from the nucleus into the cytoplasm

  9. ACTIVATION OF AMINO ACIDS: • In the cytoplasm, an enzyme attaches amino acids to tRNA molecules. Each type of amino acid is attached to its specific tRNA.

  10. mRNA passing out of the nuclear pores into the cytoplasm • triplet codons of tRNA with amino acids in the cytoplasm of the cell

  11. TRANSLATION • The start codon (AUG) end of the mRNA strand binds onto a ribosome. A tRNA carrying the amino acid methionine at one end and anticodon (UAC) at the other, binds to the mRNA start codon within the ribosome.

  12. A second tRNA binds to the next codon. Its amino acid links to the polypeptide bond of the first amino acid. • The first tRNA is released from the ribosome. The ribosome moves along the mRNA strand one codon at a time. Two tRNAs at a time are temporarily bound within the ribosome and their amino acids linked together Ribosome Amino acid forming polypeptide bond (jelly snakes) mRNA strand DNA strand Triplet codon of tRNA

  13. A polypeptide chain forms (jelly snakes) Snakes form the polypeptide chain

  14. When a ‘stop’ codon is reached the polypeptide chain is released into the cytoplasm Polypeptide chain

  15. A polypeptide chain is only the primary structure of a protein. Each protein has a particular shape formed by the twisting or folding of its polypeptide chains • Proteins are vital components of a cell.

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