We have now been introduced to the major classes of biomolecules.

  • carbohydrates
  • lipids
  • proteins
  • nucleic acids

These biomolecules work together to perform specific functions and to build important structural features of cells. For example, in the section on lipids, we first saw the diagram below of a membrane.

A lipid bilayer

In addition to the lipid bilayer, comprised of a special type of lipid, the membrane contains numerous proteins and sugars. As shown, proteins and sugars can be combined to form glycoproteins. Sugars can also be added to lipids to form glycolipids.

Many of the proteins that are important in the development and/or detection of cancer are glycoproteins. For example, diagnostic tests for prostate cancer involve testing blood samples for the presence of a glycoprotein called the prostate specific antigen or PSA. Ovarian cancers may be monitored by production of another glycoprotein called CA-125. CA stands for cancer associated.

More on the CA-125 test

Often many proteins and other biomolecules join together to form functional structures in cells. Next we will investigate some of these more complex structures, called organelles.