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Protein synthesis - Coggle Diagram

- - - - Polyadenylation of 3' end
        
        Also called a "poly-A tail" because it is made up of many adenine nucleotides
        
        CPSF binds to the poly-A-signal and CsTF binds to U or GU rich region
        
        The U or GU rich region is cleaved
        
        Polyadenylate polymerase (PAP) synthesizes the poly-A tail
      - Intron splicing
        
        Spliceosome complex
        
        Removes introns
        
        snRNA (short nuclear RNA) joins with proteins to become snRNP (short nuclear ribonucleoproteins) (also called "snurps")
        
        Snurps bind to the edge of either exon and join (spliceosome complex) to cut out the intron
        
        The introns will then be degraded by exonucleases
        
        This is called the "lariat"
        
        Alternative splicing
        
        Can cut out an exon as a byproduct
        
        This yields various isoforms (and thus, various protein structures and functions)
        
        In humans, 95% of multi-exonic genes are alternatively spliced
        
        Recall that introns are cut out and exons are spliced together
        
        Introns denote "intervening"
        
        Exons denote "expressed"
      - 5' 7-methyl cap
        
        Both the 5' cap and the poly-A tail are added to protect from RNAses (enzymes that chew up single stranded RNAs)
        
        This occurs because viral RNA is single stranded
        
        Occurs during transcription (just after initiation)
        
        The 5' end of mRNA is capped by 7-methyl-guanosine
    - - Heterogenous nuclear ribonucleoprotein
  - - - Function
      - Subunits
        
        Large and small (small attaches first)
    - - Organization
        
        amino acid attachment site
      - anticodon loop
      - Function
      - Attachment of amino acids to tRNA
    - - Redundancy of genetic code
      - 3rd position wobble
        
        The hypothesis is that the third anticodon of the tRNA doesn't always match up perfectly, to conserve the amount of unique tRNAs used (there are 61 potential anticodons and about 40 unique tRNAs)
      - mRNA read in threes, which corresponds to anticondons of tRNA
    - - Initiation
        
        Start AUG
        
        Small ribosomal subunit joins at 5' end of mRNA
        
        Methionine is the first to join
        
        The large ribosomal subunit joins
        
        The first tRNA joins at the P site, but subsequent tRNAs join at the A site
      - Elongation
        
        New amino acids are added to the polypeptide chain at the C-terminus
      - Translocation
        
        tRNA moves from A site to P site
      - Termination
        
        Eventually the stop codon is reached (UAG, UAA or UGA)
        
        A release factor comes in and the complex is disassembled
      - Most steps convert GTP to GDP