PROTEIN STRUCTURE

• HOW ARE AMINO ACIDS JOINED?

  amide linkages (a.k.a peptide bonds)

  -> -CONH2
• PRIMARY STRUCTURE OF PROTEINS?

  • fixed sequence of AAs
  • condensation polymers
  • covalent bonding
  • relatively stable
  • requires boiling with 6 moldm^-3 HCl to break peptide bonds
• SECONDARY STRUCTURE OF PROTEINS?

  • alpha helix or beta pleated sheet
  • hydrogen bonds
  • weaker than covalent bonds
  • easily disrupted
  • by gentle heating or changes to pH
• TERTIARY STRUCTURE?

  • 3D shape
  • hydrogen bonds, ionic interactions, disulfide bridges, van der Waals
  • fold into globular shapes
• HYDROLYSIS?

  • acid hydrolysis of polypeptides produces AAs
  • 6 moldm^-3 HCl
  • 24 hours
  • boiled
• HOW TO FIND PROTEIN STRUCTURE?

  • find primary structure
  • by refluxing with 6 moldm^-3 HCl
• STRETCHINESS OF WOOL?

  • protein fibre
  • held together by hydrogen bonds
  • when stretched, hydrogen bonds stretch
  • fibre extends
  • when tension released, returns to normal shape
  • washing at high temperatures can permanently break bonds and the wool can permanently lose its shape
• BONDING FOUND BETWEEN AAs?

  1. Hydrogen bonding (C=O --- H-N)
  2. Ionic attractions (NH3+ and COO-)
  3. Disulfide bridges (CH2SH + HSCH2 + [O] -> CH2S-SCH2 + H2O)