Proteins

• Amino acid structure

  
• Amino acid

  • 20 different amino acids that make proteins
  • R group differs for each amino acid
  • 2 bonded amino acids= dipeptide
  • more than 2= polypeptide
• Dipeptide

  Two amino acids bonded together

  
• primary structure


  The specific sequence of amino acids that make up a protein

  
• Secondary structure

  Coiling and pleating of parts of the polypeptide molecule

  Alpha helix and beta pleated sheets

  
• Alpha helix

  • right hand coil
  • as it coils, hydrogen bonds form
  • stabilises the protein

  
• Beta pleated sheets

  • Amino acid chain folds up on itself
  • hydrogen bonds form across sheets
  • stabilises the protein

  
• How is the tertiary structure of a protein held together?

  
  

  polar interactions, disulphide bonds, Ionic interactions and covalent bonds

  
• quatenary structure

  more than one polypeptide chain

  
• Disulphide bonds/ bridges/ linkages

  • covalent bonds
  • will bond as soon as two R groups with sulphur are close
• Ionic interactions

  • Carboxyl and amino groups form charges in solutions
  • Opposite charges come together
• 3D proteins shapes

  • Fibrous
  • Globular
• Fibrous

  • Structural functions
  • repetitive amino acid sequences
  • usually insoluble
• Globular

  • metabolic functions
  • formed through hydrophobic and hydrophilic interactions
  • water soluble