2019年雅思考试考前阅读精品练习题2

相信很多同学都知道，阅读是我们提分比较容易的一项考察科目，所以我们在平时要加强对阅读的训练，今天小编就给大家整理了这篇阅读素材，在坦途网雅思考试频道还有很多相关的内容和考试资讯，现在我们就先来看一下这篇文章吧！

Hair is curly or straight, depending upon the number of disulfide bonds between hair proteins found in the hair shaft(毛干).

The greater the number of links, the curlier the hair, and the fewer the number of links, the straighter the hair.

Hair is primarily composed of keratin(角蛋白), a protein, which grows from a sac called the follicle. Cells in the hair follicle generate keratin, and various other proteins, which become a part of the hair shaft. These proteins contain sulfur atoms, and when two of these sulfur atoms pair up and bond, they form a disulfide bond. If the two sulfur atoms in the same protein are at a distance, and join to form the disulfide bond, the protein will bend.

The amount of humidity in the air not only makes for what some label a "bad hair day," but alters the degree of curliness or of straightness of hair. This occurs when high humidity forces water back into the hair fiber, acts on its protein structure, and forces the hair shaft to return to its original structure.

People can temporarily alter their hair to force it into a straight state, or a curly state, but only on a temporary, not on a permanent, basis. When a straight-haired person gets a "permanent wave," known as a "perm(烫发),"he or she is chemically forcing the making of strong disulfide bonds. The wave does not stay permanently, because new hair, which is straight, grows in as the "perm" grows out. People with curly hair may chemically alter their hair to give it a straighter appearance, but this, too, is also a temporary solution to a permanent "problem," with the same end result.

以上就是小编为大家整理的全部内容了，在一阅读素材里，我们不仅能练习我们的阅读能力，还可以积累素材，建立我们自己的素材库，经过量的积累，我们才会有质的飞跃，小编有也会继续为大家整理相关的内容，希望大家在最后雅思考试成绩查询结果出来的时候，大家都能看到满意的结果！