**3.3 Collagen fibres**

The assembly of collagen fibrils into parallel bundles forms collagen fibres that have high strength and flexibility. When tropocollagen is assembled into collagen, it forms fibrous or sheet-like staggered structures. These fibrous structures have striations every 680 Å consisting of a dense-packed region where fibres overlap, and a loose-packed region is formed (**Figure 5**). In one single row, tropocollagen units are separated by 400 Å gaps, and these gaps are found in the loose-packed region. If the tropocollagen rows are aligned next to each other, each adjacent row is offset by 680 Å, forming a structure that repeats every five rows.

end of one tropocollagen unit and the residues near the carboxyl-end of an adjacent tropocollagen unit. The enzyme Lysyl oxidase is small enough to fit between the 400-Å gaps between the triple-helix molecules to initiate the intermolecular

Collagen maturity or the amount of cross-linking increases drastically with age of the tissue and depends on the type and function of the tissue where collagen is

Collagen has a wide range of structural roles in mammalian and aquatic tissue. It is the major constituent of skin, bone, tendon, cartilage, blood vessels and teeth. Collagen is found in almost every organ of the body, starting from skin to the cornea of the eye. To serve functions in such diverse tissues, there are different types of collagen that differ in how they interact with each other and with other tissue. There are more than 28 types of collagen identified. Collagen types I, II, III are the most abundant and most investigated for various applications. However, over 90% of the collagen found in the body is type I. The variations are due to the differences in the assembly of basic polypeptide chains, different lengths of the

Each collagen molecule is composed of three different polypeptide chains (α1, α2, and α3). Each chain is identified by its amino acid composition (**Table 2**). Collagen type I, for example, is identified for its constitution of α1 (I) and/or α2 (I) chains. The most commonly occurring variant of type I collagen consists of two α1 (I) and one α2 (I) chain. The alpha symbol is used to indicate a single chain component seen after collagen denaturation and the letter β, γ, and δ have been used to indicate covalently linked dimers, trimers or tetramers of the alpha chain.

helix, and differences in the terminations of the helical domains [24].

• Collagen type I: found in skin, tendon, organs and bone tissues.

• Collagen type IV: Forms the bases of the cell basement membrane.

development, wound healing and tissue repair.

Biodegradable Collagen possesses the feature of being biodegradable and low immunogenicity.

pharmaceutical, leather, film industry to tissue engineering.

• Collagen type III: the main component of reticular fibres, alongside type I.

• Collagen type V: the main component of cell surfaces, hair and placenta.

Collagens within the body serve largely for the maintenance and structural

Collagen has been used in many industries, from the biomedical, cosmetic,

The collagen within the body fulfils the role of entrapment, local storage, delivery of growth factors and cytokines and hence it plays an important role during organ

The most common types of collagen are:

**Function Description**

Structural integrity

Variety of applications

**Table 2.**

**211**

Entrapment and storage

*Collagen and its features [25].*

• Collagen type II: main component of cartilage.

integrity of tissues and organs.

cross-linking.

*Collagen: From Waste to Gold*

*DOI: http://dx.doi.org/10.5772/intechopen.94266*

**3.5 Collagen types**

found.

Hydrophobic and charged amino acid residues along the length of tropocollagen cause the staggered arrangement of tropocollagen. Tropocollagen units are aligned where the sum of the hydrophobic and charged region interaction between two units is strongest, hence the 680 Å staggering between units.
