C i.e. Formation Collagen is a triple helical structureQ in which 3 a chains are wound into right handed superhelix with occurance of glycine residue at every 3rd positionQ of triple helix of a-chain. Vitamin C (ascorbic acid) is necessary (as cofactor) for hydroxylation of proline & lysine while procollagen is conveed into collagen during post translational modificationQ.Removal of leader or signal sequence (to form pro a- chains), hydroxylation (not hydrolysis) of proline & lysine residues, glycosylation of some hydroxylysine not proline residues with glucose or glucosyl galctose, interchain and intrachain disulfide bond formation at carboxy terminal propeptide extension (while amino terminal extension propeptide forms only intrachain disulfide bonds) and triple helix formationQ are intracellular events of collagen formation.Cleavage of amino & carboxy terminal propeptide extensions (by N & C procollagen peptidases) releasing triple helical tropocollagen; spontaneous self assembly of tropocollagen molecules to form collagen fibrils; assembly of collagen fibrils in orderd, quaer overlapping, parallel, staggered alignment; oxidative deamination of E aminogroups of lysyl and hydroxyl lysyl residues to aldehydes; and formation of intra and inter chain covalent cross links Schiff bases and aldehyde condensation products 1/t mature collagen formation are extracellular events of collagen formation.