. 2021 Nov 9;13(22):3868. doi: 10.3390/polym13223868

Table 1.

The function of the 5 most common types of collagen.

Collagen	Function or Application	Tissue or Organ	Molecular Composition *
Type I	the organic part of the bone, membranes for guided tissue regeneration	Skin, bone, teeth, tendon, ligament, vascular ligature	${[α 1 (I)]}_{2} α 2 (I)$
Type II	the main constituent of cartilage, cartilage repair, and arthritis treatment	cartilage	${[α 1 (II)]}_{3}$
Type III	the main constituent of reticular fibers, hemostats, and tissue sealants	muscle, blood vessels	${[α 1 (III)]}_{3}$
Type IV	the major component of the basement membrane, attachment enhancer of cell culture, and diabetic nephropathy indicator	basal lamina, the epithelium-secreted layer of the basement membrane	${[α 1 (IV)]}_{2} α 2 (IV)$ ${[α 3 (IV)]}_{2} α 4 (IV)$ ${[α 5 (IV)]}_{2} α 6 (IV)$
Type V	feedstock for biomaterials in corneal treatments	Hair, cell surfaces, and placenta.	$α 1 (V), α 2 (V), α 3 (V)$

* $α 1 (I), α 2 (I), α 1 (II), α 1 (III), α 1 (IV), α 2 (IV), α 3 (IV), α 4 (IV), α 5 (IV), α 6 (IV), α 1 (V), α 2 (V),$ and $α 3 (V)$ are proteins encoded by COL1A1, COL1A2, COL2A1, COL3A1, COL4A1, COL4A2, COL4A3, COL4A4, COL4A5, COL4A6, COL5A1, COL5A2 and COL5A3 genes, respectively.