Collagen

• It comprises of short stout elongated fibrils. Many collagen fibrils come together and form a collagen
  and forma collagen fiber.
• Collagen contributes to meat toughness.
• Diameter of collagen fibers is 1- 12 um.
• Rarely seen as branched.
• Collagen fibrils are formed of long tropocollagen molecules.
• Collagen is a glycoprotein containing galactose and glucose.
• Glycine is one - third of total amino acid content of collagen followed by hydroxyproline and proline
  account for another one-third of amino acid content of collagen. Hydroxyproline is exclusive to collagen
  and due to this reason to estimate collagen normally hydroxyproline is estimation is done.
• Collagen has intermolecular cross linkages and due to these has high tensile strength of collagen
  fibers. Younger the animal lesser are the cross links.
• As the animal progresses in age the collagen cross-link concentration increases.
• Oxidative deamination initiates the cross linking through lysyl oxidase.
• Cross linking of collagen is a progressive process but it is not that it is in every muscle.
• There are about 14 types collagen. The type I, II, III comprise the bulk. Some these have been
  discussed below–
  
  
  Collagen type I
  i)The fibers have diameter between 80 to 160nm.
  ii)Found in bone, skin, tendon, muscles and walls of blood vessels.
  
  Collagen type II
  i)have a diameter <80nm
  ii)found in invertiberal discs and hyaline cartilage.
  
  Collagen type III
  i)Found in spleen, muscle, and aorta.
  
  Collagen type IV
  Found around different types of in the basement membranes and muscles.
  
  Collagen type V
  It is found in embryonic cell cultures and the basement membranes.
  
  Collagen type VI
  It is found in muscle and skin.
  
  
  Tropocollagen
• High molecular weight protein 300,000 daltons.
• Formed of three polypeptide strands forming triple helix.
• The binding cross links of the tropocollagen molecules are made between the helical shaft of one molecule
  and the non-helical extension of the neighboring molecule.
  
  Elastin
• It is less abundant as compared to collagen.
• It is a rubbery protein.
• It is found in ligaments ( e.g. ligamentum nuchae ) , walls os arteries, organs and muscles,
• It has a high content of glycine.
• It contains 8 amino acids.
• The two amino acids specific to elastin are desmosine and isodesmosine. Desmosine forms cross links
  and it binds 4 adjoining elastin chains by forming intermolecular linkage between their molecules due to
  non polar amino acids and desmosine cross links.