* Collagen: This is a fibrous protein found in many animals and provides structural support. In sponges, collagen forms the basic framework of the body.
* Spongin: This is a unique protein found only in sponges. It's a type of collagen with a high concentration of the amino acid tyrosine. Spongin forms the tough, flexible fibers that give sponges their characteristic shape and texture.
So, while there isn't one single protein that makes up a sponge, it's a combination of collagen and spongin that creates their structure.
