Subunit

• Collagen is broken into subunits called tropocollagen. Tropocollagen is a polypeptide chain which form a triple helix affixed with hydrogen bonds.
  
  

Components

• Collagen is composed of predominately amino acids. It contains high concentrations of both glycine and proline, as well as hydroxyproline and hydroxylysine. Vitamin C is not a direct component of the amino acid chain but is necessary to the collagen building process.
  
  

Types

• There are 29 identified collagen fiber types. Most of the collagen in the body is type 1,2,3 or 4. Collagen type one is found in soft tissues including skin, internal organs, tendons and bones. Type 2 collagen in located in the body's cartilage structures. Collagen type 3 is found in reticular membranes and tissues. Type 4 collagen is found in cell-basement membranes.
  
  

Formation

• In vivo formation is collagen formation which occurs inside the cell. Three peptide chains form along the rough endoplasmic reticulum inside the ribosomes. In vitro formation occurs outside the cell. Collagen is formed in a laboratory by manual processes.
  
  

Fiber

• Collagen is a chain of five tropocollagen molecules. Its amino acid base makes it a protein strand. Tropocollagen molecules have a staggered arrangement. This allows them to join to adjacent strands, and provides the fibers with added strength.