WHAT ARE MACROMOLECULES ?
Colloidal solutions are formed by aggregation of atoms or molecules to give particles of
colloidal size. Yet there are substances which are themselves composed of giant molecules and
dissolve in a solvent to yield colloidal solutions directly. These giant molecules are termed
macromolecules. The dimensions of the macromolecules fall in a range between 10Å and 10,000Å.
Proteins (gelatin), synthetic polymers (plastics), synthetic rubber, cellulose and starch all possess
Solutions of macromolecules behave like reversible colloids or lyophilic sols. They show a weak
Tyndall effect and possess high viscosity. Macromolecules in solution do not carry an electric
charge and do not show electrophoresis.
Molecular weight of Macromolecules
The molecular weight is an important property of polymeric substances such as proteins,
polymers (plastics, starch) and other macromolecules. Generally, molecules of a protein or a polymer
may not be of the same size. Therefore all the experimental methods of molecular weight determination
will give some kind of an average value. Two types of average molecular weights have been defined.