Proteins

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  • Created by: Mazza24
  • Created on: 23-11-15 21:13
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  • Proteins
    • contain the elements C,H,O,N,S
      • are large polymers formed from amino acid sub-units.
        • there are 20 different types of amino acids = infinite possible amino acid arrangements
    • shape
      • function- is closely related to its shape
      • determines the protein by the sequence of amino acids in the protein
    • differences
      • differ through having different R-groups
    • Condensation
      • With the loss of water peptide bonds are formed between the amino acids
      • takes place between one of the amino group of the amino acids and the carboxyl group of another linking the carbon and nitrogen together
      • two amino acids joined together form a dipeptide
    • hydrolysis
      • peptide bond can be broken with the release of the two constituent amino acids with the addition of water
    • many amino acids joined together with peptide bonding= polypeptide
    • protein structure
      • Secondary
        • amino acids in a poly peptide chains contain -NH and -C=O on either sides of the peptide bonds
          • the O of  the carboxyl gp, has a negative charge where as the N of this Amino gp, has a positive charge. This causes hyrdrogen bonds to form
        • most common types:
          • a-helic- hydrogen bonds are formed between the amino acids occuring at regular intervals. These hyrdogen bonds twist them into a spiral shape
          • beta- pleated sheet
            • more rigid and less flexible configurations than a-helix. formed by sections of the polypeptide chain into anti parallel directions lying adjacent to each other.
            • hydrogen bonds form between -C=O and NH groups
      • Tertiary
        • further folding of secondary structure - gives it its unique 3D shape
          • consequence of a range of bonds formed between the R-groups of amino acids in the chain
        • bonds
          • hydrogen
            • relatively weak and easily broken
          • ionic
            • formed between amino and carboxyl groups. are stonger than hydrogen bonds but are damaged by changes of pH
          • disulphide
            • colvanet bonds formed bwtween R-groups of sulfur containing amino acids. are very strong and are important in giving strength to structural proteins such as collagen.
      • primary
      • quarternary
        • consist of two or more polypeptides bonded together
        • some quarternary proteins contain non-protein components (prosthetic groups) that are intergranal in their function. These conjugated proteins include glycoprotein- is important in structure
          • e.g. Haemoglobin
    • types of protein
      • fibrous
        • consist of polypeptides arranged in chains that form fibres or sheets. these parallel chains are linked by cross-bridges to form very strong and stable molecule. are invariably structural in function.
          • e.g. collagen - wound round each other and held together by hydrogen bonds. Collagen is found in tendons that link muscle to bone.
      • globular
        • have a metabolic role and include enymes and antibodies. proteins ability to form very specific 3-D shapes is crucial to their role as enzymes and antibodies
          • e.g. haemoglobin

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