Globular proteins are proteins that consist of long chains of amino acids folded up into complex shapes. Globular proteins serve as, or form important components of, the following:

 

· Enzymes
· Hormones
· Antibodies

 

Some globular proteins have a structural role. For example, globular proteins form part of the cell membrane, which has a structural role as well as a role in transporting ions in and out the cell.

 

The structure of globular proteins has been traditionally discussed in terms of four levels of structure: primary, secondary, tertiary, and quaternary. Two additional levels are now commonly distinguished: motifs and domains.

 

The other main type of protein, in terms of its structure, is fibrous protein.