The 40 nm gap in between the tropocollagen molecule in collagen which serves as the site of bone formation is occupied by which of the following
In bone, entire collagen triple helices lie in a parallel, staggered array. 40 nm gaps between the ends of the tropocollagen subunits serve as nucleation sites for the deposition of long, hard, fine crystals of the mineral component, which is (approximately) hydroxyapatite, Ca5(PO4)3 (OH), with some phosphate.
Carbohydrate
Ligand moiety
Ca++
Fe++