35 Amino acids are joined in a protein by the formation of a peptide bond + H 3 N C C N C C O - + H 2 O H R 1 H R 2 O O H + H 3 N C C O - + + H 3 N C C O-H R 1 H R 2 O O Peptide (amide) bond Dipeptide â contains two amino acid residues planar. 36 20 amino acids can form 20 2 or 400 dipeptides.
Hydroxylapatite, also called hydroxyapatite (HA), is a naturally occurring mineral form of calcium apatite with the formula Ca 5 (PO 4) 3 (OH), but is usually written Ca 10 (PO 4) 6 (OH) 2 to denote that the crystal unit cell comprises two entities.Hydroxylapatite is the hydroxyl endmember of the complex apatite group.The OH â ion can be replaced by fluoride, chloride or carbonate, producing fluorapatite or chlorapatite. It crystallizes in the hexagonal crystal system.ydroxylapatite is the hydroxyl endmember of the complex apatite group. The OH â ion can be replaced by fluoride, chloride or carbonate, producing fluorapatite or chlorapatite. It crystallizes in the hexagonal crystal system.
Stalagmites and stalactites contain calcium carbonate (CaCO 3). Calcium carbonate is the basis of the cement industry. Calcium is classified chemically as one of the alkaline earth elements (that is, in Group 2 of the periodic table.The metal is rather reactive. It readily forms a white coating of calcium nitride (Ca 3 N 2) in air.alcium is an essential constituent of leaves, bones, teeth, and shells. Calcium is the fifth most abundant element in the earth's crust and makes up more than 3% of the crust. Calcium does not occur as the metal itself in nature and instead is found in various minerals including as limestone, gypsum and fluorite.