Proteins

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  • Proteins
    • functions
      • structural components eg muscle and bone
      • membrane carriers and pores eg active transport and facilitate diffusion
      • all enzymes are proteins
      • many hormones are proteins
      • antibodies are proteins
    • There large molecules called polymers
      • they are made by joining monomers
        • these are made of amino acids
          • there are 20 main amino acids
          • all amino acids have the same basic structure by their r group differs
            • eg the r group in glycine is a hydrogen atom bonded to the second carbon
          • they contain the elements carbon, hydrogen, oxygen and nitrogen
    • a polypeptide chains is the backbone of a protein chain
      • amino acids bond together in a condensation reaction to form a dipeptide
        • as more and more amino acids join a polypeptide is formed
      • both polypeptide and proteins are made on ribosomes during protein synthesis
      • as mRNA passes through ribosome amino acids join together
    • the function of each protein is determined by its structure
      • Primary structure
        • the order of specific amino acids
        • only peptide bonds are involved
        • worked on by Fredrick Sanger
      • secondary structure
        • polypeptide chains fold to form a coiled alpha helix or beta-pleated sheet
        • hydrogen bonds hold the coils in place
      • tertiary structure
        • a final three dimensional shape is built  when the coils and pleats coil and fold themselves
        • various points on the secondary structure are attracted t each other (intermolecular bonds)
      • Quaternary structure
        • made of more than one polypeptide unit or a polypeptide inorganic component
        • e.g. insulin and haemoglobin

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