Protein Types

• The 2 main types of protein?
  • Fibrous
  • Structure is long and coiled with little to no tertiary structure, have occasional crosslinks between chains which form fibers.
  • They are insoluble and very strong also denaturing resistant.
  • For example Collagen has 3 polypeptide chains (1000 amino acids long), wound into a triple helix then microfibrils and fibers
    • It is used to add strength to tendons, ligaments and bones
  • Globular
  • Large proteins with tertiary and sometimes quaternary structure
  • Hydrophilic on outside and hydrophobic on inside
    • An example is Hemoglobin, very large, 4 peptide chains and an iron prosthetic group. Hormones and antibodies are also globular

Conjugated proteins

• Proteins with another molecule attached called a prosthetic group. For example;
  • Haemaglobin - iron prosthetic group
  • Chlorophyll - magnesium prosthetic group

Denaturing

Denature - Protein loosing it's shape due to changes in conditions there are 2 types

• Permanent such as
  • Heat
  • Thermal energy disrupt hydrogen bond and causes protein to unfold
  • Heavy metals
  • React with sulfhydryl group to form stable metal Sulphur bonds
  • Prevents formation of disulphide bonds needed for the protein to form the correct shape
  • Ag,Hg and Pb all do this
• Temporary such as
  • pH
  • Change in ph changes amino acid from a zwitterion and makes it charged this alters solubility and shape while pH is changed