Plants synthesize and store starch inside specialized cellular structures called amyloplasts. Photosynthesis first produces simple glucose building blocks, which chemists call monomers. Enzymes then link these monomers together to create dense, long-term energy storage.
Amylose makes up about twenty to thirty percent of a typical starch sample. It consists of individual alpha-D-glucose molecules linked together by alpha-1,4-glycosidic bonds. These specific chemical bonds cause the long chain to coil into a tight helix.
Amylopectin makes up the remaining seventy to eighty percent of the starch material. It contains the exact same straight alpha-1,4 linkages found in amylose. However, it also features alpha-1,6-glycosidic branching points every twenty-four to thirty units.
These frequent branches create a massive and highly complex molecular architecture. In humans, starch digestion naturally begins in the mouth using salivary amylase. The digestion process continues in the small intestine using a similar pancreatic amylase.
These enzymes break the complex chains down into maltose and eventually free glucose. Human cells then burn this free glucose for cellular respiration and energy. Starch powder does not dissolve at all when mixed into cold water.
However, it undergoes a rapid process called gelatinization when heated in a liquid. The starch granules absorb the hot water molecules and swell up irreversibly.