ATP molecules are essentially little battery packs that move through the cell providing energy for all the cell's processes, and you get through a lot of it. At any given moment, a typical cell in your body will have about one billion ATP molecules in it, and in two minutes every one of them will have been drained dry and another billion will have taken their place. Every day you produce and use up a volume of ATP equivalent to about half your body weight. Feel the warmth of your skin. That's your ATP at work.
ATP分子实质上就像一组小小的电池，它们在细胞内移动，为细胞活动提供全部能量，在此过程中你获益匪浅。在你生命的每一瞬间，你体内的每个细胞内通常具有10亿个ATP分子，2分钟以后它们的能量都会消耗殆尽，然后又会有10亿个新的ATP分子接替它们的位置。每天你产生和消耗的ATP重量大约是你体重的一半。摸一摸你温热的皮肤，那是你的ATP在工作。

When cells are no longer needed, they die with what can only be called great dignity. They take down all the struts and buttresses that hold them together and quietly devour their component parts. The process is known as apoptosis or programmed cell death. Every day billions of your cells die for your benefit and billions of others clean up the mess. Cells can also die violently—for instance, when infected—but mostly they die because they are told to. Indeed, if not told to live—if not given some kind of active instruction from another cell—cells automatically kill themselves. Cells need a lot of reassurance.
当细胞不再被需要时，它们以堪称高贵的方式死去。它们拆下所有支撑它们的支柱和拱壁，不露声色地吞噬掉其组成部分。这一过程被称为凋亡或细胞死亡机制。每天都有数十亿个细胞为你而死，又有数十亿个别的细胞为你清扫它们的遗体。细胞也可能暴死——比如当你被感染时——但在大多数情况下它们是按照指令死去的。事实上，如果它们没有收到继续活着的指令——如果没有收到另一个细胞发出的活动指令，细胞会自己杀死自己。细胞真是太需要安慰了。
When, as occasionally happens, a cell fails to expire in the prescribed manner, but rather begins to divide and proliferate wildly, we call the result cancer. Cancer cells are really just confused cells. Cells make this mistake fairly regularly, but the body has elaborate mechanisms for dealing with it. It is only very rarely that the process spirals out of control.
在偶然情况下，细胞没有按指令死去，相反却开始拼命分裂和扩散，这种情况我们称之为癌症。癌细胞其实不过是迷途的细胞。细胞经常犯类似的错误，但是人类身体具有一种纠正这种错误的复杂机制，只是在极其偶然的情况下，细胞的活动才会失去控制。