Pectins are linear polyaccharides that are the cement in cell walls of many non-woody plant parts. The short chains are soluble, but not digested by humans and, therefore, are a source of soluble fiber. Pectin is especially high in citrus fruits and is also used as a gelling agent for jams. Pectin is made of a repeating galacturonic acid monomer. Alduronic acids (like galacturonic acid) are oxidized sugars with the primary alcohol group (C-6, in this case) oxidized to a carboxylic acid. Every second carboxylic acid group in the galacturonic acid chain is methylated in pectin. The repeating galacturonic acid monomers are connected by a-(1->4) bonds. Below draw 4 repeating monomer units making up a pectin molecule