Biol 1 - Proteins

Notes for AQA BIOL 1 AS Proteins

  • Created by: Stephanie
  • Created on: 10-05-12 19:51

Protein structure

Monomer = Amino Acid
Polymer = Polypeptide chain 

Formation = condensation reaction (a molecule of water is released)
Breakdown = hydrolysis reaction 

Structure of Amino Acids

All have on fully saturated Carbon molecule
Attached to it are:

  • One Carboxcylic acid group (COOH)
  • One Amine Group (H23)
  • One H group
  • One 'R' Group (varies between molecules, e.g, Glycine is H, Alanine is CH3) 
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Structural Levels

Primary Structure = sequence of amino acids

Secondary Structure = Hydrogen bonds form between amino acids to form either an Alpha Helix (coils) or Beta Pleated Sheets (like a consontinia)

Tertiary Structure = More bonds form between different parts of the peptide chain
                                This is the final 3D structure for single chained proteins

Quaternary Structure = Bonds form between multiples polypeptide chains
                                      Final 3D structure for multiple chained proteins 

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Functions of Proteins

  • Enzymes
  • Antibodies
  • Transport Proteins - contain hydrophobic and hydrophilic amino acids causing the protein to fold and form a channel
  • Structural Proteins - e.g, Collagen in connective tissues & Keratin in teeth and nails
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Biuret Test

The test for Proteins-

  • Test solution needs to be alkaline so sodium hydroxide solution added
  • Add copper (II) sulphate:
    - If protein is present it turns purple
    - Otherwise stays blue 
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