Structural proteins are used to build structural components of the body, such as bones and cartilage. The most common example of a structural protein is collagen which is found in the bones, cells and skin.
Structural proteins are also found in cells. They are used to provide an internal structure to the cell and are sometimes involved in cell movement. Structural proteins are especially important in larger cells.
Collagen is the most abundant example of a structural protein and accounts for around a quarter of all proteins in the body. Under a microscope, collagen cells look like long fibres that are woven together to create extra strength.
The purpose of collagen is to support tissues in the body and to provide structure for specific types of cells. Collagen is also responsible for the elasticity of skin, which is why skin becomes wrinkled when it lacks collagen. The body uses collagen in blood vessels, ligaments and tendons.
All proteins are large molecules which are built from many other smaller molecules. These smaller molecules are called amino acids. When amino acids are joined together in different combinations, they form proteins with different properties. Other types of proteins include hormones, enzymes and carrier molecules.
Other types of structural proteins include keratins, actins and myosins, which are found in muscle tissue and the silks and insect fibers. Keratins form protective coverings for skin, fur, hair, wool, claws, nails, hooves, horns, beaks and feathers. Collagen is found in the tendons and hides of vertebrates. The tendons and hides form connective ligaments inside the body and give extra support to parts of the skin.