proteins

• Proteins

  peptides are polymers made up of amino acid molecules

  proteins made of one or more polypeptides arranged as complex macromolecules

  contain C,H,O and N
• Amino acids 


  same basic structure different R-groups

  amine group - NH2

  carboxyl group - COOH ( acidic )

  r group - R

  central alpha carbon

  20 different amino acids

  5 non-essential

  9 essential

  6 conditionally essential (infants/ growing children)
• synthesis of peptides


  amine + carboxylic acid group react

  carboxylic acid of one amino acid reacts with the hydrogen in the amine group of another amino acid forming a peptide bond

  condensation reaction

  resulting in a dipeptide
• Polypeptide


  when many amino acids are joined together by a peptide bonds

  catalysed by peptidyl transferase (in ribosomes)
• Folding of polypeptides - Primary structure 


  The sequence in which amino acids are joined

  the order of bases -> order of amino acids
• Folding of polypeptide chains - Secondary structure 


  folded primary chain

  alpha helix - hydrogen bonds form in the amino acid chain

  beta pleated sheets - polypeptide chains parallel to each other joined by H+ bonds
• Folding of polypeptides - Tertiary structure

  final-folding - interaction between R group

  • hydrogen bonds - weakest bonds to form
  • ionic interactions - stronger than hydrogen, forms between oppositely charged R - groups
  • disulfide bridges - strongest are covalent which only form between R groups with sulfur
  • non-polar molecules - hydrophilic and hydrophobic interaction (weak) between polar and non-polar
• Folding of polypeptides- Quaternary structure 


  Results from the association of two or more individual proteins - subunits

  final folding and finishing

  happens in the endoplasmic reticulum and golgi apparatus
• Hydrophilic and hydrophobic interactions


  assembled in the aqueous environment of the cytoplasm

  folds differently depending on R-group (hydrophilic/hydrophobic)

  hydrophilic - outside the molecule

  hydrophobic - inside the molecule
• Breakdown of peptides


  Protease catalyses reverse reaction

  hydrolysis reaction