多糖Polysaccharide

糖苷键的构型决定多糖的形态与功能。淀粉中的直链淀粉以 α-1,4 键连接，形成螺旋，能包合碘分子呈蓝色；支链淀粉和糖原另有 α-1,6 分支，糖原分支更密，可迅速动员葡萄糖。纤维素以 β-1,4 键连接成伸直的长链，链间大量氢键形成微纤丝，强度高。甲壳素是 N-乙酰葡糖胺的 β-1,4 聚合物，构成节肢动物外骨骼。

The configuration of the glycosidic bond determines shape and function. Amylose, the linear part of starch, is α-1,4 linked and coils into a helix that traps iodine to give a blue colour; amylopectin and glycogen add α-1,6 branches, more densely in glycogen, which allows rapid release of glucose. Cellulose is β-1,4 linked into straight chains held by many hydrogen bonds into strong microfibrils. Chitin, the β-1,4 polymer of N-acetylglucosamine, forms arthropod exoskeletons.

1811 年基希霍夫发现用酸可将淀粉水解为葡萄糖。1838 年佩扬从植物细胞壁中分离出纤维素并命名。1857 年伯尔纳在肝脏中发现糖原。1920 年施陶丁格提出高分子学说，指出纤维素、淀粉等是由共价键连接的长链大分子，而不是小分子的缔合体，获 1953 年诺贝尔化学奖。

In 1811 Kirchhoff found that acid hydrolyses starch to glucose. Payen isolated cellulose from plant cell walls and named it in 1838. Claude Bernard discovered glycogen in the liver in 1857. In 1920 Staudinger proposed that cellulose, starch and similar substances are long chains held by covalent bonds, not associations of small molecules; his macromolecular theory earned the 1953 Nobel Prize in Chemistry.

淀粉是人类主要的能量来源，也用于生产葡萄糖浆、乙醇和可降解材料；纤维素用于造纸、棉纺、粘胶纤维和纤维素衍生物（醋酸纤维、羧甲基纤维素）；人体不能消化的膳食纤维有助于肠道健康。透明质酸、肝素、壳聚糖、海藻酸钠等多糖在医药和食品领域应用广泛。

Starch is humanity's main energy source and is also made into glucose syrup, ethanol and biodegradable materials; cellulose goes into paper, cotton, viscose rayon and derivatives such as cellulose acetate and carboxymethyl cellulose; indigestible dietary fibre supports gut health. Hyaluronic acid, heparin, chitosan and sodium alginate are widely used in medicine and food.