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It may seem counterintuitive, but every day that you've barely been able to get out of bed,
这看起来似乎有悖常理，但每天你都几乎无法起床，
and every time that you struggled to keep your eyes open while cramming for a test at 1 am,
每次你在凌晨1点准备考试的时候都要睁大眼睛，
you've actually had a lot of energy. I'm not talking about motivation or enthusiasm, I mean real, physical, energy.
你真的需要有很多精力。我说的不是动机或热情，我指的是真实存在的，身体上的能量。
We might be used to energy as a big picture concept, that having energy allows us to move our bodies and do work.
我们可能习惯于把能量作为一个宏大的概念，即有了能量，我们就可以操纵身体去活动。
That's totally true, but cells also need energy to move their bodies, manufacture new proteins, and make chemical reactions happen.
这是完全正确的，但是细胞也需要能量来运作，制造新的蛋白质，并发生化学反应。
And that's the focus of this episode, energy at the very tiny level.
这就是这一期的焦点话题，能量处于非常微小的水平。
Today, we're going to learn how we turn the molecules from food into usable energy.
今天，我们将学习如何将食物中的分子转化为可用的能量。
What do we mean when we say that energy is important?
当我们说能量是重要的是什么意思？
Well, some of our biological processes require energy to turn reactants into products,
嗯，我们的一些生物反应过程需要能量来将反应物转化为产物，
chemistry terms for the chemicals you start with and the chemicals you end with.
化学术语是指开始和结束使用的化学物质。
Our bodies have a few ways of doing this, namely extracting energy-rich molecules from the food you eat and turning it into energy.
我们的身体有几种方法可以做到这一点，即从你吃的食物中提取富含能量的分子，并将其转化为能量。
That's where a molecule called adenosine triphosphate, or ATP, comes in.
这就是三磷酸腺苷分子的来源。
As the name implies, this molecule has three phosphates.
顾名思义，这个分子有三种磷酸盐。
But it's the bonds between them that we're more interested in.
但我们更感兴趣的是它们之间的联系。
The chemical bonds that hold those phosphates together hold a lot of energy.
将这些磷酸盐结合在一起的化学键含有大量的能量。
When one of those phosphates is broken off, that ATP becomes ADP, or adenosine diphosphate plus one loner phosphate.
当这些磷酸盐中的一种被破坏时，三磷酸腺苷变成二磷酸腺苷，或二磷酸腺苷加上一个单独的磷酸盐。
That transformation of ATP to ADP results in usable energy that our cells can use to power our biological processes.
但正是三磷酸腺苷向二磷酸腺苷的转化产生了可用的能量，我们的细胞可以利用这些能量为我们的生物过程提供动力。
So that begs the question — where does ATP come from?
所以这就引出了一个问题-三磷酸腺苷是从哪里来的？
Well you see, when an adenosine and a triphosphate fall in love,
你看，当一个腺苷和一个三磷酸坠入爱河的时候，
they… I'm kidding! Our bodies' main way of making ATP involves using carbohydrates,
它们……我开玩笑的！我们身体制造三磷酸腺苷的主要方式包括使用碳水化合物，
especially a simple but important molecule called glucose.
是一种特别简单但很重要的分子葡萄糖。
Try not to think of carbohydrates as mini tortillas floating around in your cells,
不要把碳水化合物想象成漂浮在细胞中的微型玉米饼，
but as what they really are: molecules of carbon, hydrogen, and oxygen, hence carbo-hydrate.
而要把它们想象成真正的分子：碳分子，氢和氧，因此是碳水合物。
The first thing we do is put that glucose molecule through the process of glycolysis.
我们要做的第一件事就是让葡萄糖分子经历糖酵解的过程。
Glyco for sugar, and lysis because we're breaking it apart.
糖和糖酵解，因为我们要把它分离开。
That glucose molecule gets broken down into another molecule called pyruvate,
葡萄糖分子被分解成另一个叫做丙酮酸的分子，
plus another molecule that becomes useful a little later on.
再加上另一个稍后会用得到的分子。
Glycolysis actually takes a little bit of ATP to happen, but it ends up netting us two ATP molecules,
糖酵解过程的进行实际上需要一点点三磷酸腺苷，但它最终会使我们获得两个三磷酸腺苷分子，
which is awesome, we will definitely use those two ATP.
这是可怕的，我们一定会使用这两个三磷酸腺苷。
This entire reaction happens without oxygen, it's anaerobic.
整个反应在没有氧气的情况下进行，这是厌氧的。
But our bodies can extract way more ATP if they use an additional aerobic pathway, meaning they do use oxygen.
但我们的身体可以提取更多的三磷酸腺苷，如果使用额外的有氧途径，这意味着它们确实需要使用氧气。
Some simple organisms, like the bacteria that causes botulism can fuel their entire existence off of anaerobic pathways like glycolysis.
一些简单的生物体，如引起肉毒中毒的细菌，可以通过糖酵解等厌氧途径为它们的生存提供养料。
But in our bodies, glycolysis is just the first step to cranking out a lot of ATP.
但是在我们的身体里，糖酵解只是产生大量三磷酸腺苷的第一步。
By the end of glycolysis, we have two pyruvates, two ATP molecules and two molecules of NADH,
在糖酵解结束时，我们有两个丙酮酸盐，两个三磷酸腺苷分子和两个还原型辅酶Ⅰ分子，
a molecule that we can't extract energy from but we can repurpose as ingredients in a different reaction.
它是一种我们不能从中提取能量的分子，但我们可以在不同的反应中重新利用它作为成分。
Now, glycolysis happens in the cytosol, the liquid within your cells.
现在，糖酵解发生在细胞内，细胞内的液体。
But like we learned in the last episode, we've got a secret weapon, a BEHEMOTH of energy production.
但就像我们在上一期学到的，我们有一个秘密武器，一个生产能量的庞然大物。
We have mitochondria. I know! We spent so much of the last episode talking about mitochondrial DNA
这个就是线粒体。我知道！上一期我们花了很多时间讨论线粒体DNA
and endosymbiosis and today we finally get to talk about its powerhouse-ness.
和内共生体，今天我们终于谈到了它的强大功能。
I'm excited too, okay, let's go.
我也很兴奋，好吧，接着说这个吧。
So after glycolysis, we shuttle that pyruvate and those NADH towards the mitochondria, where we're going to make even more ATP.
所以糖酵解后，我们把丙酮酸和还原型辅酶Ⅰ转移到线粒体，在那里我们会产生更多的三磷酸腺苷。
After all is said and done we're going to end up with more than thirty ATP.
毕竟这些都说过并试验过，我们将最终有超过30三磷酸腺苷分子。
Our cells like to work smarter, not harder, so they use molecules called enzymes.
我们的细胞喜欢更智能地工作，而不是更努力地工作，所以它们使用称为酶的分子。
Enzymes are chemicals that lower the amount of energy required for that reaction to happen.
酶是降低反应发生所需能量的化学物质。
I like to think of enzymes as coupons for chemistry.
我喜欢把酶看作化学的试金石。
You get the same product in the end, but instead of spending a lot of energy,
最终你会得到同样的产物，但你不需要消耗大量的能量，
you apply an enzyme, and you get the same product for a lot less energy.
而是使用一种酶，你可以用更少的能量得到同样的产物。
And this next process, the Krebs Cycle, has multiple enzymes helping it along.
下一个过程，柠檬酸循环，有多种酶促使这个循环的进行。
Wait! Don't click away yet! Look, I get it.
等等！先别急着离开！听着，我明白了。
I've had to memorize this thing three separate times throughout my schooling because I kept on forgetting it.
我不得不在学校里分别背这东西三次，因为我老是把它忘了。
That's the real Kreb's Cycle. You learn the Kreb's cycle, then forget the Kreb's cycle, so you learn the Kreb's Cycle
这才是真正的柠檬酸循环。你学习了柠檬酸循环，然后忘记了柠檬酸循环，你再去学习柠檬酸循环
and then you're spiraling forever in the nerdiest episode of Black Mirror ever written.
然后你就会在《黑镜》有史以来最无聊的一集里不停地循环。
But once you see the big picture of this cycle, you'll come to appreciate it as I have.
但是一旦你看到这个循环的全貌，你就会像我一样欣赏它。
Remember, the purpose of all this is to make ATP, and we can make a lot of ATP if we can use oxygen.
记住，所有这些的目的是制造三磷酸腺苷，如果我们可以使用氧气，我们就能制造大量的三磷酸腺苷。
But we need to prep our materials in such a way that lets us use oxygen.
但是我们需要这样来准备我们的原料，让我们可以使用氧气。
Pyruvate itself has three carbon atoms. Along comes a chemical that bumps one of them off,
丙酮酸本身有三个碳原子。伴随而来的是一种化学物质，它会把其中的一个弄掉，
turning it into a molecule with two carbon atoms.
把它变成一个含有两个碳原子的分子。
This new product is called Acetyl CoA and it's a big deal in the Krebs Cycle.
这种新产物叫做乙酰辅酶A，它在柠檬酸循环中是很重要的。
Next, we add a four-carbon molecule to Acetyl CoA to make a molecule with six carbons called citrate.
接下来，我们在乙酰辅酶A中加入一个四碳分子，形成一个六碳分子，称为柠檬酸盐。
The Krebs cycle is also called the citric acid cycle because of this molecule.
因为这个分子，克雷布斯循环也被称为柠檬酸循环。
So by this point, we have a modest four ATP — 2 from glycolysis, and two more from the Krebs Cycle.
至此，糖酵解产生了4个三磷酸腺苷，2个来自糖酵解过程，另外2个来自克雷布斯循环过程。
But the more interesting products are the ten molecules of NADH and the newly created two molecules of FADH2.
但更有趣的产物是10个还原型辅酶Ⅰ分子和新产生的2个黄素腺嘌呤二核苷酸递氢体分子。
These things are really gonna pay off in the next step.
这些产物在下一步中一定会奏效的。
Manipulating these leftover ingredients will get us a lot of ATP.
控制这些剩余的成分会给我们带来很多三磷酸腺苷。
It's a process called oxidative phosphorylation. Again, big science words, but it means exactly what it says.
这是一个叫做氧化磷酸化的过程。再说一次，大科学词汇，但它的意思就是完全一样的。
We're going to shuffle around phosphate and use oxygen. In order to contain and process that energy,
我们要用磷酸盐和氧气混洗。为了保存和处理能量，
the NADH and FADH2 molecules transfer their electrons along a series of steps called the electron transport chain.
还原型辅酶Ⅰ和黄素腺嘌呤二核苷酸递氢体分子沿着称为电子传递链一系列步骤转移它们的电子。
They present their electrons to the mitochondria's inner membrane
它们将电子提供给线粒体的内膜，
where electron transporters move them towards the inside of the mitochondria.
在那里电子转运体将它们移向线粒体的内部。
This process releases some energy, which sets up a smooth gradient of Hydrogen ions across the mitochondrial membrane.
这个过程释放出一些能量，从而在线粒体膜上建立起一个平稳的氢离子梯度。
This gradient can be used to power ATP synthase, an enzyme that helps put a phosphate on ADP, turning it into ATP.
这个梯度可以用来给三磷酸腺苷合酶提供能量，三磷酸腺苷合酶是一种酶，有助于将磷酸作用于二磷酸腺苷，将其转化为三磷酸腺苷。
After you tally everything up, you realize how much energy you generated.
当你把所有的原理都了解后，你就会意识到你产生了多少能量。
You gained two ATP directly from glycolysis and two more from the Krebs cycle.
你从糖酵解中直接获得了两个三磷酸腺苷，从克雷布斯循环中又获得了两个。
Each of those ten NADH molecules can get us up to 3 ATP, and each of the two FADH2 can yield two ATP.
这十个还原型辅酶Ⅰ分子中的每一个都能使我们获得3个三磷酸腺苷，两个黄素腺嘌呤二核苷酸递氢体中的每一个都能产生2个三磷酸腺苷。
That's a total of 38 molecules of ATP for every molecule of glucose under prime conditions.
在最佳条件下，每分子葡萄糖含有38个三磷酸腺苷分子。
You also ended up with water and carbon dioxide as byproducts. How cool is that!
你最终还会得到副产品水和二氧化碳。多酷啊！
We went from 2 ATP per molecule of glucose to 38 by adding oxygen and a few enzymes.
我们通过添加氧气和一些酶，将每分子葡萄糖从2个三磷酸腺苷增加到38个三磷酸腺苷。
Now, we can extract ATP from a few other molecules. Glucose itself is a simple carbohydrate,
现在，我们可以从其他几个分子中提取三磷酸腺苷。葡萄糖本身是一种简单的碳水化合物，
but we can also utilize more complex carbohydrates by breaking them into simpler versions.
但我们也可以利用更复杂的碳水化合物，把它们分解成更简单的形式。
Then they go through a similar cycle to before — glycolysis, Kreb's cycle, and oxidative phosphorylation.
然后它们经历一个与糖酵解前相似的循环--克雷布斯循环和氧化磷酸化。
Of course, it would be great if we just always had a batch of glucose on hand to use whenever we needed it.
当然，如果我们总是有一批葡萄糖在需要的时候就可以拿来用，这当然非常好，我们需要它。
Like, we always have some dissolved glucose in our blood that our cells can use,
就像，我们的血液中总有一些溶解的葡萄糖供我们的细胞使用，
but it's constantly increasing or decreasing depending on things like food, exercise, time of day, or whether or not you have diabetes.
但是它在不断地增加或减少，这取决于食物，运动，一天中的某一刻，或者你是否有糖尿病。
And low blood glucose can get dangerous, especially if your brain doesn't have enough glucose since that's the only fuel source it can use.
而且低血糖会变得危险，特别是如果你的大脑没有足够的葡萄糖，因为那是它唯一可以使用的能量来源。
Well, unless you're starving. As a workaround, our bodies convert spare glucose into an easily useable storage form of glucose called glycogen.
嗯，除非你饿了。作为一种解决办法，我们的身体将多余的葡萄糖转化为一种容易使用的葡萄糖储存形式，称为糖原。
This starchy substance is kept mostly in the liver and skeletal muscle, and can be tapped whenever your body needs some quick energy.
这种淀粉物质主要保存在肝脏和骨骼肌中，当你的身体需要一些能量时，它可以迅速被利用。
Your liver can sense when overall blood glucose is low and chip off some glycogen to get used as fuel,
你的肝脏可以感觉到总血糖很低然后消耗一些糖原作为能量，
and your muscles can use glycogen if they need more energy during exercise.
如果你的肌肉在运动中需要更多的能量，它们可以使用糖原。
Now, stored fat is a more energy-dense molecule than glucose.
现在，储存的脂肪是比葡萄糖能量密度更大的分子。
However, fat is more than just energy storage, it's a whole organ unto itself.
然而，脂肪不仅仅是能量储存，它本身就是一个完整的器官。
But for now, we'll focus on how we extract so much ATP from it.
但现在，我们将专注于如何从其中提取如此多的三磷酸腺苷。
When our bodies want to use some of our stored fat,
当我们的身体想要使用一些储存的脂肪时，
it first needs to break it into fatty acids and glycerol.
首先需要将其分解成脂肪酸和甘油。
By the end of its processing, we end up with some familiar ingredients — acetyl CoA, NADH, and FADH2.
在分解过程结束后，我们得到了一些熟悉的成分--乙酰辅酶A、还原型辅酶Ⅰ和黄素腺嘌呤二核苷酸递氢体。
Then that acetyl CoA goes into the Kreb's Cycle, just like if it came from a glucose molecule.
然后乙酰辅酶A进入克雷布斯循环，就像它来自葡萄糖分子一样。
However, what makes using a molecule of fat different than a molecule of glucose is the total ATP payoff.
然而，使用与葡萄糖分子不同的脂肪分子的原因是三磷酸腺苷的总收益。
For a typical molecule of fat with sixteen carbons, we'll end up with twenty one molecules of ATP from NADH,
对于一个典型的有16个碳原子的脂肪分子，我们最终会从还原型辅酶Ⅰ中得到21个三磷酸腺苷分子，
fourteen from FADH2, and ninety six from Acetyl CoA for a whopping total of a hundred and thirty one molecules of ATP.
14个来自黄素腺嘌呤二核苷酸递氢体，96个来自乙酰辅酶A，总共含有131个三磷酸腺苷分子。
Although, caveat here, this isn't a concrete number since fat comes in multiple carbon combinations.
不过，请注意，这并不是一个具体的数字，因为脂肪是由多种碳组成的。
But either way, it's a lot of ATP. Now, molecules of fat are bigger than molecules of glucose,
但不管怎样，都是大量的三磷酸腺苷P。现在，脂肪分子比葡萄糖分子大，
but a gram of fat still nets you two and a half times more ATP than a gram of glucose.
但是一克脂肪仍然比一克葡萄糖多摄取2.5倍的三磷酸腺苷。
That's what makes it such a great way of storing energy. But that's only one of the amazing functions of our fat.
这就是为什么它是一种非常好的储存能量的方式。但这只是我们脂肪惊人的功能之一。
In the next episode, we're gonna talk about fat as an organ and learn about all the other things it does aside from storing energy.
在下一期中，我们将讨论脂肪作为一个器官，并学习它除了储存能量之外所做的所有其他知识。
Thanks for watching this episode of Seeker Human, I'm Patrick Kelly.
感谢收看这期的《Seeker Human》，我是帕特里克·凯利。
