Tertiary structure

• The alpha helix or beta pleated sheet can also be arranged in various ways which give the protein its 3D shape.
• The tertiary structure is vital because proteins mainly work on the basis of their shape.
• The tertiary structure of a protein is determined by R groups. These can form different types of bonds with the R groups of nearby amino acids, and these hold the shape firmly in place.
• Bonds that maintain the tertiary structure:

  • Disulphide bonds - protect against heat
  • Ionic bonds - If R groups are oppositely charged
  • Hydrogen bonds
  • Hydrophilic and Hydrophobic interactions - hydrophobic generally are inside the protein when in solution
• If an R group has no charge it is hydrophobic and soluble amino acids are normally charged.