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Protein. The most important and chemically most complex category of organic compounds found in nature, whose basic building blocks are amino acids (q.v.) that are synthesized only by plants from simple inorganic substances and in which nitrogen (q.v.) forms the most characteristic constituent. The elemental composition of proteins averages 50-55% carbon, 20-23% oxygen, 12-19% nitrogen, with some also including minor amounts of sulfur, phosphorus, iodine and certain metals. They range in their molecular weight (q.v.) from 6,000 for the smallest molecules (q.v.) to many millions for the largest molecules, and vary in their gross structural conformations from long polypeptide chains (q.v.), fibrillar and pleated-sheet forms, to folded and globular forms. The type of structure found in a specific protein category depends on the type of bonding that links the individual amino acids. In wheat flour (q.v.), gliadin (q.v.) and glutenin (q.v.) are the two major proteins involved in gluten (q.v.) formation in dough (q.v.). Gluten plays a vital role in determining the quality of the baked product.