Disaccharides
Disaccharidesare carbohydratedimers. These dimers are formed from two monomers by dehydrationsynthesis. Any two monosaccharides can form a disaccharide. Forexample, maltose is formed by the dehydration synthesis of two glucosemolecules. Sucrose, common table sugar, comes from the linkage of onemolecule of glucose and one of fructose.
二糖
二糖化合物,这些二聚体是由两个单体脱水缩合形成。任何两个单糖可以形成一个糖。举例来说,麦芽糖是由脱水合成二葡萄糖分子。蔗糖,淀粉,是由葡萄糖和果糖组成的。
Polysaccharides
Polysaccharides can consist of as few asthree and as many as several thousand monosaccharides. Depending ontheir structure and the monosaccharides they contain, polysaccharidescan function as a means of storing excess energy or provide structuralsupport.
When cells ingest more carbohydrates thanthey need for fuel, they link the sugars together to formpolysaccharides. The structure of these polysaccharides is different inplants and animals: in plants, polysaccharides take the form of starch, whereas in animals, they are linked in a structure called glycogen.
Polysaccharides can also have structuralroles in plants and animals. Cellulose, which forms the cell walls ofplant cells, is a structural polysaccharide. In animals, thepolysaccharide chitin forms the hard outer armor of insects, crabs,spiders, and other arthropods. Many fungi also use chitin as astructural carbohydrate.
多糖
多糖可以构成多达数千种。根据其结构和它们含有单糖,多糖的所具有的功能,所以多糖可以储存过剩的能源或提供结构性支持。
当细胞摄取碳水化合物比他们需要消耗的多时,他们链接起来在一起,形成多糖结构,植物和动物的多糖不相同:在植物中,多糖存在形式是淀粉,而在动物,他们链接一起后存在形式是糖元。
多糖也可以有结构性的角色,在植物和动物。在植物细胞中纤维素构成细胞壁,纤维素就是是一个结构性的多糖。在动物方面,多糖甲壳素形式铠甲如昆虫,螃蟹,蜘蛛,和其他节肢动物的壳。许多真菌也利用甲壳素作为一个结构性碳水化合物。
Proteins
More than half of the organic compounds incells are proteins, which play an important function in almost everycellular process. Proteins, for example, provide structural support tothe cell in the cytoskeleton and make up many of the hormones that sendmessages around the body. Enzymes, which regulate chemical reactions in the cell, are also proteins.
蛋白质
蛋白质在半数以上的有机化合物细胞中发挥了重要的作用。例如,支持细胞膜结构的骨架和输送激素到身体的各个部位。在细胞中酶调节化学反应,也是靠蛋白质。(因为酶就是一种蛋白质)
Amino Acids
Proteins are made up of monomers calledamino acids. The names of many, but not all, amino acids end in -ine:methionine, lysine, serine, etc. Each amino acid consists of a centralcarbon atom attached to a set of three designated groups: an atom ofhydrogen (–H), an amino group (–NH2), and a carboxyl group (–COOH). The final group, designated (–R) in the diagram below, varies between different amino acids.
It is possible to make an infinite number of amino acids by attaching different compounds to the R position of the central carbon. However, only 20 types of R groups exist in nature, so there are only 20 naturally occurring amino acids.
氨基酸
氨基酸是蛋白质的单体。他的名称很多,都以INE结尾:蛋氨酸,赖氨酸,丝氨酸等,每个氨基酸组成的中央碳原子上都连有3个基团这是不会变的: 1原子氢( - H )的,一氨基酸组(-NH2) ,和一个羧基( -COOH) 。最后一组,都是R基( - R )在如下图,R基决定氨基酸的不同。
这也就是说可以有无数种的氨基酸,只要中央碳的支链上有不同的R基。但是,在性质上只有20个类型的R群体存在所以只有20种氨基酸。
多肽
这20个氨基酸的部分或全部制成所有的蛋白质的链。两个氨基酸间-NH2与-OH之间称作一个肽键2个集团组合到一起的过程就叫脱水缩合
氨基酸为其主要结构, 某一特定蛋白质有特定的氨基酸序列,这是众所周知。每一个蛋白质在三维立体空间中经过一系列的过程如卷等这些都是都预定好的。具有一个独特的2级(初步绕组和卷取)和三级结构(整体折叠) 。在苛刻的条件,如高温或极端的pH值,蛋白质可能会失去其正常的形状和停止运作。一个蛋白生活在苛刻的条件,它会发生“变性” 。