Starch

Starch is a plant-produced polysaccharide of glucose that stores energy. Its two components, amylose and amylopectin, differ in how their glucose chains are arranged.

Glucose: A simple sugar that serves as a major energy source and building block for larger carbohydrates. Glucose units are the repeating building blocks joined to make starch.
Starch synthase: An enzyme that extends glucan chains during starch biosynthesis. It builds α(1→4)-linked chains that become part of starch.
Gelatinization: The heat-and-water-driven swelling and structural disruption of starch granules. It thickens many cooked foods as starch granules take up water.
Glycogen: A highly branched glucose polymer that stores energy in animals and fungi. Both store glucose, but glycogen is generally more highly branched and serves different organisms.
Amylose: A mostly linear polymer of glucose with chains linked by α(1→4) bonds. This starch component forms relatively straight chains that can coil into helices.
Branching enzyme: An enzyme that creates branch points in glucan chains by forming α(1→6) bonds. It introduces the branches characteristic of amylopectin.
Retrogradation: The reassociation of gelatinized starch chains during cooling or storage. It explains firming, staling, and some changes in the texture of starch-rich foods.
Cellulose: A structural plant polysaccharide made of glucose units linked by β(1→4) bonds. Its different bond geometry makes cellulose structural and resistant to human digestion, unlike dietary starch.
Amylopectin: A branched glucose polymer with α(1→4) chains and α(1→6) branch points. Its branching distinguishes the other major component of starch and affects how starch swells.
ADP-glucose: An activated glucose donor used by plants to synthesize starch. Starch synthases transfer its glucose onto growing starch chains.

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