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Amylose is a polysaccharide made of α-D-glucose units, bonded to each other through α(1→4) glycosidic bonds. It is one of the two components of starch , making up approximately 20–30%. Because of its tightly packed helical structure, amylose is more resistant to digestion than other starch molecules and is therefore an important form of ...
It consists of two types of molecules: the linear and helical amylose and the branched amylopectin. 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.
Due to strong associations of hydrogen bonding, longer amylose molecules (and starch which has a higher amylose content) will form a stiff gel. [6] Amylopectin molecules with longer branched structure (which makes them more similar to amylose), increases the tendency to form strong gels. High amylopectin starches will have a stable gel, but ...
Starch is mostly composed of amylopectin and amylose, but amylopectin has been shown to degrade more easily. The reason is most likely because amylopectin is highly branched and these branches are more available to digestive enzymes. In contrast, amylose tends to form helices and contain hydrogen bonding. [23]
Retrogradation is a reaction that takes place when the amylose and amylopectin chains in cooked, gelatinized starch realign themselves as the cooked starch cools. [1]When native starch is heated and dissolved in water, the crystalline structure of amylose and amylopectin molecules is lost and they hydrate to form a viscous solution.
By the 1980s, the presence of polyiodide chains within the amylose helix became widely accepted. [8] However, the precise composition/structure of these chains, including the balance between molecular iodine and various iodide anions, continues to be debated and investigated, with a 2022 article suggesting that they might alternate.
Two common examples are cellulose, a main component of the cell wall in plants, and starch, a name derived from the Anglo-Saxon stercan, meaning to stiffen. [2] To name a polysaccharide composed of a single type of monosaccharide, that is a homopolysaccharide, the ending “-ose” of the monosaccharide is replaced with “-an”. [3]
The chair conformation of six-membered rings have a dihedral angle of 60° between adjacent substituents thus usually making it the most stable conformer. Since there are two possible chair conformation steric and stereoelectronic effects such as the anomeric effect, 1,3-diaxial interactions, dipoles and intramolecular hydrogen bonding must be taken into consideration when looking at relative ...