Protein Synthesis

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  • Protein Synthesis
    • DNA Base Sequence
      • represents code for primary protein structure (amino acid sequence)
      • 3 adjacent bases are required to code for a single amino acid.
        • Triplet code: Allows 64 different triplet, but there are only 20 amino acids.
          • Some amino acids have >1 triplet= DEGENER-ATE CODE.
      • Contains INTRONS (non coding sections) and EXONS (sections that code for amino acids)
    • Transcription
      • Occurs in the nucleus
      • Converts DNA to mRNA for a single gene or protein.
      • 1) DNA unzips at specific gene location- Hydrogen bonds break.
        • 2) RNA nucleotides align:sugar-phosphate backbone forms.
          • Phospho-diester bonds between nucleotides form.
          • CATALYSED by RNA Polymerase.
      • 2) RNA nucleotides align:sugar-phosphate backbone forms.
        • Phospho-diester bonds between nucleotides form.
        • CATALYSED by RNA Polymerase.
      • 3) mRNA detaches from DNA= pre-mRNA
        • DNA double helix reforms.
      • 4) Pre-mRNA  converted to mRNA before releases through nuclear pores.
    • DNA double helix
      • In nucleus
        • Codes for all genes
      • 2 strands of nucleotide, held together by  H bonding; coiled around each other.
    • Modifying pre-mRNA to form mRNA.
      • 4) Pre-mRNA  converted to mRNA before releases through nuclear pores.
      • INTRONS are removed from pre-mRNA by enzymes
        • This gives mRNA.
        • Introns remain inside nucleus whilst  exons exit.
    • Translation
      • Occurs are RIBOSOMES
      • mRNA sequence used to assemble protein
      • a) Enzyme Activation
        • Bonds a specific amino acid to a specific tRNA  molecule.
          • tRNA: Single strand, but complementary pairs when it coils, forming a clover leaf shape.
            • Folding of RNA creates an ANTICODON at one end.
      • b) Assembly of polypeptide
        • Ribosome reads mRNA Codons
          • This allows a complemen-tary tRNA Anticodon to align and bind.
            • Adjacent amino acids form peptide bonds by condensation.
      • tRNA detaches and 'picks up' another specific amino acid.
      • Polypeptide released once a 'stop' codon is reached.

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