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Protein Synthesis

Protein Synthesis. Biology 12. Protein Synthesis. Think of a cell as a miniature factory that makes, among other things, all the different kinds of proteins that organisms need. Ex. Structural Enzymes Hormones Antibodies. Protein Synthesis.

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Protein Synthesis

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  1. Protein Synthesis Biology 12

  2. Protein Synthesis • Think of a cell as a miniature factory that makes, among other things, all the different kinds of proteins that organisms need. • Ex. • Structural • Enzymes • Hormones • Antibodies

  3. Protein Synthesis • All of the proteins are made from a pool of 20 different amino acids that are found floating around in the cytoplasm of the cell. • The instructions needed for the exact sequence of amino acids to synthesize the correct proteinare encoded on genes located along the rails of the DNA double helix.

  4. Protein Synthesis • These instructions never leave the nucleus. • So, just how can DNA direct the synthesis of a protein without directly taking part in it?

  5. The Process • Quick summary:

  6. Transcription • A small section of DNA unwinds and unzips in the nucleus.

  7. Transcription • RNA polymerase joins complementary nucleotides (A,U,C,G) to the DNA strand from a pool of nucleotides in the nucleus.

  8. Transcription • The strand of mRNA grows attached to the DNA strand.

  9. Transcription • The mRNA detaches and the DNA strands rewind.

  10. Transcription • mRNA is ready to exit the nucleus through pores in the nuclear membrane.

  11. Transcription • Every 3 nucleotides of mRNA = 1 codon

  12. Translation • The decoding of codons of mRNA into actual proteins. • It takes place at the ribosomes.

  13. Translation • Ribosomes are made of rRNA (ribosomal RNA). • They have 2 parts, 1 large subunit and 1 small subunit. • Each ribosome has a binding site for mRNA and 2 tRNA molecules.

  14. Translation • tRNA is a single strand of RNA that has folded back onto itself. • The complementary base pairs cause this to happen.

  15. Translation • tRNA base pairs with mRNA at the ribosome. • As base pairing occurs, amino acids bond together to form peptide bonds to make proteins.

  16. Translation • Polyribosomes: • These are bunches of several ribosomes that move along mRNA at once. • Several proteins can be built at one time. • They can be as close as 80 base pairs apart on the mRNA.

  17. Translation • Translation requires 3 steps: • Chain initiation • Chain elongation • Chain termination

  18. Translation • Chain initiation: • The polypeptide (protein) chain begins. • tRNA UAC binds with mRNA AUG at the ribosome.

  19. Translation • Chain Elongation: • Ribosome moves along the mRNA. • The polypeptide chain grows longer as amino acids are added.

  20. Translation • Chain termination: • The tRNA anticodon binds to a stop codon. • The ribosomal subunits separate. • The protein is released.

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