Primary protein structure

• Which direction is the amino acid sequence written in

  N to C
• Condensation reactions


  1. Produce peptide bonds

  2. Release water
• What are the features of peptide bonds

  • Between N and C
  • Very strong covalent bonds
• Key features of peptide chains

  1. Grow in the N to C direction

  2. Amino acids are only added to the C terminal
• What is a hydrolysis reaction

  1. Break the peptide bonds

  2. Use water
• Rotational features of the pepptide bond

  • Restricted rotation of peptide bond restricts protein folding
  • Hydrogen and Oxygen atoms sit on opposite sides of the bond
  • Partial dipole across the peptide bond
• Psi (Ψ) bond


  Fits between the chiral carbon and the carbon in the peptide bond
• Phi (Φ) bond


  Fits between Chiral atom and the nitrogen in the peptide bond
• Psi and Phi bonds


  Allow for rotation in protein folding
• Main characteristics of protein folding

  • Steric collisions - Residue groups restrict phi/psi angles
  • Psi and Phi bonds determine 3D shape
  • Energetically stable structures prevent natural unfolding
  • Hydrophobic collapse theory details how hydrophobic residues are packed towards the interior of the protein
  • Proteins form hydrogen bonds with water molecules in order to neutralise the backbone charge
• What is the backbone charge of a protein


  Polarity of the molecule due to the polar C=O and N-H groups