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Starch (a polymer of glucose) is used as a storage polysaccharide in plants, being found in the form of both amylose and the branched amylopectin. In animals, the structurally similar glucose polymer is the more densely branched glycogen, sometimes called "animal starch". Glycogen's properties allow it to be metabolized more quickly, which ...
Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight. [4] Glycogen, the energy reserve of animals, is a more highly branched version of amylopectin. In industry, starch is often converted into sugars, for example by malting.
To generate energy, the plant hydrolyzes the starch, releasing the glucose subunits. Humans and other animals that eat plant foods also use amylase, an enzyme that assists in breaking down amylopectin, to initiate the hydrolysis of starch. [3] Starch is made of about 70–80% amylopectin by weight, though it varies depending on the source.
How humans developed the ability to digest starch: A study offers insight into the evolution of amylase genes, which are key to breaking down some carbs.
In plants and some prokaryotes, glucose is a product of photosynthesis. [69] Glucose is also formed by the breakdown of polymeric forms of glucose like glycogen (in animals and mushrooms) or starch (in plants). The cleavage of glycogen is termed glycogenolysis, the cleavage of starch is called starch degradation. [87]
Starches have been classified as rapidly digestible starch, slowly digestible starch and resistant starch. [25] Starches in plants are resistant to digestion (resistant starch), but cooking the starch in the presence of water can break down the starch granule and releases the glucose chains, making them more easily digestible by human digestive ...
Amylose is important in plant energy storage. It is less readily digested than amylopectin; however, because of its helical structure, it takes up less space than amylopectin. As a result, it is the preferred starch for storage in plants. It makes up about 30% of the stored starch in plants, though the percentage varies by species and variety. [13]
Both animals and plants temporarily store the released energy in the form of high-energy molecules, such as adenosine triphosphate (ATP), for use in various cellular processes. [3] Humans can consume a variety of carbohydrates, digestion breaks down complex carbohydrates into simple monomers (monosaccharides): glucose, fructose, mannose and ...