Proteins

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  • proteins
    • structure - the number, sequence and type of amino acids to form a chain
      • primary - linear sequence of amino acids
      • secondary - when a chain of amino acids coils into an alpha helix or folds into a beta pleated sheet caused by hydrogen bonds forming between the R-groups of some amino acids
      • quaternary - when a protein is made up of more  than one polypeptide
        • haemoglobin - made up of 4 polypeptides but 2 different types with a prosthetic group called Haeme in each one, each Haeme has an Iron (Fe) ion in the centre
        • collagen - 3 polypeptides which are the same type, it is known as a fibrous protein and is very strong
      • tertiary  - the folding or coiling of an alpha helix or a beta pleated sheets held together by various types of bonds
        • ESSENTIAL FOR ITS FUNCTION e.g to be a certain shape for substrates to fit into the active site (enzymes).
        • hydrophobic interactions - some R groups are hydrophobic therefore need to be held inside the protein, to do this they often bond with other hydrophobic R groups
        • disulfide bridges - covalent bonds between sulphurs in the R group of Cysteine
        • ionic bonds - between amino acids where the R group carries a charge
        • hydrogen bonds - between oxygen and hydrogen
    • types
      • globular - enzymes, antibodies and hormones
      • fibrous - collagen (fibrous role)
    • test for protein: add biuret reagent to a sample, the sodium hydroxide and copper sulfate in the solution will react with the peptide bonds, if protein is present the colour will change from a pale blue to lilac
    • amino acids - 20 amino acids which we get from our diet
      • all amino acids are identical except for the variable R group
        • it is the R group that changes the properties of the amino acids
        • the simplest R-group is H, this a.a is glycine
    • dipeptide
      • when two amino acids join together it is a condensation reaction where water is eliminated and a peptide bond is formed between the two amino acids
      • a polypeptide is a chain of amino acids that could be hunders or thousands of a.a kong
  • tertiary  - the folding or coiling of an alpha helix or a beta pleated sheets held together by various types of bonds
    • ESSENTIAL FOR ITS FUNCTION e.g to be a certain shape for substrates to fit into the active site (enzymes).
    • hydrophobic interactions - some R groups are hydrophobic therefore need to be held inside the protein, to do this they often bond with other hydrophobic R groups
    • disulfide bridges - covalent bonds between sulphurs in the R group of Cysteine
    • ionic bonds - between amino acids where the R group carries a charge
    • hydrogen bonds - between oxygen and hydrogen

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