脂肪、糖和蛋白质都是维持人体生命活动的基本物质。糖类化合物的种类很多,就其分子组成来讲有单糖、双糖和多糖。市场出售的葡萄糖,以及果糖、木糖、半乳糖、甘露糖、鼠李糖等都是单糖。它们是糖类大家族中最基本的单位,由它们还可以组成双糖和多糖化合物。例如我们经常食用的蔗糖就是由葡萄糖和果糖组成的双糖。蔗糖广泛分布在植物的根、茎、叶和果实内。植物的多糖是由成千上万个分子的单糖相连聚 Fat, sugar and protein are the basic substances that maintain the life activities of human beings. There are many types of carbohydrates, monosaccharides, disaccharides and polysaccharides in terms of their molecular composition. Glucose sold on the market, as well as fructose, xylose, galactose, mannose, rhamnose, etc. are all monosaccharides. They are the most basic unit of the large family of sugars that can also form disaccharide and polysaccharide compounds. For example, sucrose, which we regularly consume, is a disaccharide composed of glucose and fructose. Sucrose is widely distributed in plant roots, stems, leaves and fruits. Plant polysaccharides are monomeric polysaccharides linked to thousands of molecules