Making collagen matrix hard
Byung-Ho Kang
In response to my comment about extracellular matrix that
distinguishes plants from animal, one student asked how some collagen-
based extracellular matrix of an animal becomes bone which is harder
than the plant cell wall. Let me briefly explain.
When we were developing in our mother's womb, our boney skeletons were
not so hard as they are now. They arose from cartilage, the soft
material that you can fill when you touch your ear lobes or nose.
Cartilage consists of collagen and proteoglycan. Collagen is a protein
making long fibers. Proteoglycan is a huge tree-shaped molecule making
a gel-like substance by binding to a large amount of water molecules.
Once cartilage accumulates calcium phosphate, the cartilage transforms
into hard bones. We still have cartilage at the ends of bones. It
lubricate bone movements.