collagen - a fibrous scleroprotein in bone and cartilage and tendon and other connective tissue; yields gelatin on boiling

elastin - a fibrous scleroprotein found in elastic tissues such as the walls of arteries

gelatin, gelatine - a colorless water-soluble glutinous protein obtained from animal tissues such as bone and skin

chondrin - a substance that resembles gelatin and is obtained by boiling cartilage in water

ceratin, keratin - a fibrous scleroprotein that occurs in the outer layer of the skin and in horny tissues such as hair feathers nails and hooves

simple protein - a protein that yields only amino acids when hydrolyzed