Proteins 蛋白质
Different proteins can appear very different and perform diverse functions (e.g. the water-soluble antibodies involved in the immune system and the water-insoluble keratin of hair, hooves and feathers). Despite this, each one is made up of amino acid subunits.
There about 20 different amino acids that all have a similar chemical structure but behave in very different ways because they have different side groups. Hence, stringing them together in different combinations produces very different proteins.
不同的蛋白质可以看起来非常不同，并发挥不同的功能（例如，参与免疫系统的水溶性抗体和头发、蹄子和羽毛的水不溶性角蛋白）。尽管如此，每一种都是由氨基酸亚单位组成的。
大约有20种不同的氨基酸，它们都有类似的化学结构，但由于它们有不同的侧基，所以表现得非常不同。因此，将它们以不同的组合串在一起，会产生非常不同的蛋白质。
Each amino acid has an amino group (NH2) and a carboxylic acid group (COOH). The R group is a different molecule in different amino acids which can make them neutral, acidic, alkaline, aromatic (has a ring structure) or sulphur-containing.
When 2 amino acids are joined together (condensation) the amino group from one and the acid group from another form a bond, producing one molecule of water. The bond formed is called a peptide bond.
Hydrolysis is the opposite of condensation and is the breaking of a peptide bond using a molecule of water.
每个氨基酸都有一个氨基（NH2）和一个羧基（COOH）。在不同的氨基酸中，R基是不同的分子，这可以使它们成为中性、酸性、碱性、芳香族（有环状结构）或含硫。
当2个氨基酸连接在一起时（缩合），其中一个的氨基和另一个的酸基形成一个键，产生一个水分子。形成的键被称为肽键。
水解与缩合相反，是用一个水分子打破一个肽键。
Due to the bonding and the shape and chemical nature of different amino acids, the shape of a whole chain of amino acids (a polypeptide or protein) is specific.
This will affect the properties of the protein, just as the type of a necklace depends on the type of beads and how they are strung together. Therefore, the primary structure depends on the order and number of amino acids in a particular protein.
For example:Haemoglobin is made up of 4 polypeptide chains, 2α chains and 2β chains, each with a haem group attached. There are 146 amino acids in each chain. If just one of these is wrong, serious problems can arise (e.g. sickle cell anaemia). The red blood cells become distorted, the amount of oxygen they can carry is reduced and blood capillaries can be blocked, leading to acute pains called crises.
由于不同氨基酸的结合以及形状和化学性质，一整条氨基酸链（多肽或蛋白质）的形状是特定的。
这将影响蛋白质的特性，就像项链的类型取决于珠子的类型和它们的串联方式。因此，主要结构取决于特定蛋白质中氨基酸的顺序和数量。
例如：血红蛋白是由4条多肽链组成的，2α链和2β链，每条链上都有一个血红素基团。每条链上有146个氨基酸。只要其中一个出错，就会出现严重的问题（如镰状细胞贫血）。红细胞变得扭曲，它们能够携带的氧气量减少，毛细血管可能被堵塞，导致被称为危机的急性疼痛。
This is the basic shape that the chain of amino acids takes on. The 2 most common structures are the α-helix and the β-pleated sheet.
这是氨基酸链所呈现的基本形状。两种最常见的结构是α螺旋和β褶皱片。
