Starch

Starch is the stored form of sugars in plants. It is made up of a mixture of amylose and amylopectin, both polymers of glucose.

Plants synthesize glucose through photosynthesis. The excess glucose, beyond the plant’s immediate energy needs, is stored as starch in areas including the roots and seeds. The starch in the seeds provides food for the plant embryo as it germinates, and is also a source of food for humans and other animals.

Animals that consume starch must break it down into digestible sugars using enzymes, such as salivary amylases. Such enzymes break apart the polysaccharide chain into simpler sugars such as maltose and glucose. The cells can then absorb the glucose.

Starch is made up of glucose monomers that are joined by α 1,4 or α 1,6 glycosidic bonds. The numbers 1,4 and 1,6 refer to the carbon number of the two residues that have joined to form the bond. Because of the way the subunits are joined, the glucose chains have a helical structure.