enzyme 酶比任何其他成分（哪怕DNA，毕竟有些细胞没有DNA也能活）都更有资格称为生命的必备成分。

http://www.im.cas.cn/kxcb/wswdjt/201310/t20131014_3952580.html http://phymath999.blogspot.com/2015/07/dna_97.html 酶在生物体内的作用是什么？

每一种生物的生命过程，从小到大，繁衍生息，生老病死，新陈代谢，都和酶有关。如果没有酶的催化，于性命攸关的最基本的食物消化，氧的呼吸都不可能进行，更不要说其它问题。实际上生物体内发生的各种反应几乎都是由酶催化进行。可以说没有酶也就没有生命。         　　酶在生命中如此重要，其原因在于酶催化的反应速度快，要比化学催化剂催化的反应大约要快几千倍到上亿倍。比如食物中的葡萄糖与氧反应，变成二氧化碳和水，释放能量是维持生物体体温和一切活动的能源。如果没有催化剂，在常温常压条件下，需要几年或更长的时间。若要反应加快速度，必需在三百度以上才能进行，燃烧氧化，释放能量。这在生物体内是绝对不可能的。而在生物体内，在一系列酶的催化作用下，于常温常压下可瞬间完成，其速度之快难以想象。 　　另一个原因是一种酶只催化一种物质发生一种反应，或者化学类似物质的相同反应，对其它物质和反应绝对不会有催化作用；绝大多数酶只催化一种物质的一种反应，即使结构非常相似的物质也不会反应。这种性质被称为酶催化的专一性。比如葡萄糖氧化酶，只催化葡萄糖的醛基氧化为葡萄糖酸一种反应，决不会催化葡萄糖的其它基团反应，更不会催化其它物质的氧化反应。为了完成生物体内的成千上万物质的变化和反应，就需要相应的酶，有人估计，在生物体内大约存在1023种酶。是它们保证了生命过程的正常进行，一旦由于某原因造成某一种酶的缺失，或催化活性低下，生物的新陈代谢就会不正常，进而发生疾病，甚至死亡。 How Do Enzymes Work? by Joseph Castro, Live Science Contributor   |   April 26, 2014 08:52am ET 67   32   394 Submit 29 Reddit A 3D model of pepsin, an enzyme that digests food proteins into peptides. Credit: lculig / Shutterstock.com View full size image Enzymes are biological molecules (typically proteins) that significantly speed up the rate of virtually all of the chemical reactions that take place within cells. They are vital for life and serve a wide range of important functions in the body, such as aiding in digestion and metabolism. Some enzymes help break large molecules into smaller pieces that are more easily absorbed by the body. Other enzymes help bind two molecules together to produce a new molecule. Enzymes are highly selective catalysts, meaning that each enzyme only speeds up a specific reaction. The molecules that an enzyme works with are called substrates. The substrates bind to a region on the enzyme called the active site. There are two theories explaining the enzyme-substrate interaction. In the lock-and-key model, the active site of an enzyme is precisely shaped to hold specific substrates. In the induced-fit model, the active site and substrate don't fit perfectly together; instead, they both alter their shape to connect. Whatever the case, the reactions that occur accelerate greatly — over a millionfold — once the substrates bind to the active site of the enzyme. The chemical reactions result in a new product or molecule that then separates from the enzyme, which goes on to catalyze other reactions. Here's an example: When the salivary enzyme amylase binds to a starch, it catalyzes hydrolysis (the breakdown of a compound due to a reaction with water), resulting in maltose, or malt sugar.