There are two major classes or types of proteins: globular and fibrous proteins. Globular means globe-like. Hemoglobin is a good example of a globular protein. Globular proteins are quite fragile and can be inactivated (denatured) by things like heat (think of the protein albumin in an egg white when you fry it), organic solvents, or strong ionic solutions.

Fibrous proteins are much stronger and tougher. As the name implies, these proteins are more like ropes or cables. Fibrous proteins give the body structural support and help it resist mechanical stress. Common examples of body structures containing fibrous proteins include bone, cartilage, tendons (which anchor muscles to bones), ligaments (which anchor bones to other bones), and capsules around our internal organs.

The two images below show the molecular image representations of a globular (first) and a fibrous protein (second).