Nature's smallest factory: The Calvin cycle - Cathy Symington

翻译人员: Becky Zhao 校对人员: Jenny Yang

You're facing a giant bowl

你面前放着一只大碗

of energy packed Carbon Crunchies.

盛满了活力碳素早餐脆片。

One spoonful. Two. Three.

一勺，两勺，三勺

Soon, you're powered up by the energy surge

很快，你的身体就充满了能量

that comes from your meal.

这些能量来源于你的食物。

But how did that energy get into your bowl?

但是那些能量是如何进入你的碗里呢？

Energy exists in the form of sugars

能量以糖的形式存在

made by the plant your cereal came from,

那些糖分来自谷物，

like wheat or corn.

比如小麦和玉米。

As you can see, carbon is the chemical backbone,

如你所知，碳是非常重要的化学元素，

and plants get their fix of it

植物们固定碳

in the form of carbon dioxide, CO2,

是以二氧化碳（CO2）的形式，

from the air that we all breath.

由我们呼吸的空气中获得。

But how does a plant's energy factory,

但存在于叶绿体基质中的

housed in the stroma of the chloroplast,

植物的能量工厂是如何

turn a one carbon gas, like CO2,

将气态的碳，像CO2，

into a six carbon solid, like glucose?

转换为像葡萄糖这样 有六个碳原子的固体？

If you're thinking photosynthesis, you're right.

如果你想到是光合作用， 那就对了。

But photosynthesis is divided into two steps.

但是光合作用是分为两步。

The first, which stores energy from the sun

第一步，是把来自太阳的能量

in the form of adenosine triphosphate, or ATP.

转化为三磷酸腺苷，或称为ATP.

And the second, the Calvin cycle, that captures carbon

第二步，是卡尔文循环，吸收碳

and turns it into sugar.

并将其转化为糖。

This second phase represents one of nature's

这第二步代表了自然界

most sustainable production lines.

最可持续的生产线之一。

And so with that, welcome to world's most miniscule factory.

因此现在， 欢迎来到世界上最微小的工厂。

The starting materials?

原材料？

A mix of CO2 molecules from the air,

空气中含CO2分子的混合物，

and preassembled molecules called

预先安装的分子称为

ribulose biphosphate, or RuBP,

二磷酸核酮糖，即RuBP，

each containing five carbons.

每个分子含五个碳原子。

The initiator? An industrious enzyme named rubisco

引发剂？是勤劳的加氧酶

that welds one carbon atom from a CO2 molecule

它催化CO2分子中的碳原子

with the RuBP chain

与RuBP结合

to build an initial six carbon sequence.

形成初始的六碳原子序列。

That rapidly splits into two shorter chains

很快又分裂成两部分

containing three carbons each

每一部分有三个碳原子

and called phosphoglycerates, or PGAs, for short.

这个叫做磷酸甘油酸盐， 简称PGAs。

Enter ATP, and another chemical called

加入ATP, 和另一种叫做

nicotinamide adenine dinucleotide phosphate,

磷酸酰胺腺嘌呤二核苷酸的物质，

or just NADPH.

简称NADPH。

ATP, working like a lubricant, delivers energy,

ATP就像个润滑剂传递能量，

while NADPH affixes one hydrogen to each of the PGA chains,

NADPH将每个PGA链上 沾上一个氢，

changing them into molecules called

把它变成

glyceraldehyde 3 phosphates, or G3Ps.

甘油醛三磷酸分子， 或叫G3Ps.

Glucose needs six carbons to form,

葡萄糖需要六个碳组成，

made from two molecules of G3P,

从两个G3P分子中来，

which incidentally have six carbons between them.

这样他们每个都有六个碳。

So, sugar has just been manufactured, right?

所以，糖就这样产生了，是吗？

Not quite.

还没呢。

The Calvin cycle works like a sustainable production line,

卡尔文循环就像一个 可持续的生产线，

meaning that those original RuBPs

意味着那些原始的RuBPs

that kicked things off at the start,

在开始出现的，

need to be recreated by reusing materials

需要被用重用材料重新创造

within the cycle now.

在一个周期内。

But each RuBP needs five carbons

但是每个RuBP需要五个碳。

and manufacturing glucose takes a whole six.

制造葡萄糖需要六个碳。

Something doesn't add up.

这看起来不太对。

The answer lies in one phenomenal fact.

原因是一个惊人的事实。

While we've been focusing on this single production line,

虽然我们关注这个单一生产线，

five others have been happening at the same time.

另外还有五个在同时进行。

With six conveyor belts moving in unison,

六个传送带一起移动，

there isn't just one carbon that gets soldered

不仅仅是一个碳被焊接

to one RuBP chain,

到RuBP链，

but six carbons soldered to six RuBPs.

而是六个碳焊到了六个RuBP链上。

That creates 12 G3P chains instead of just two,

这样就创建了12个G3P链 而不是两个，

meaning that all together, 36 carbons exist:

意味着36个碳同时存在：

the precise number needed to manufacture sugar,

制造糖需要准确的数量，

and rebuild those RuBPs.

并重建RuBPs。

Of the 12 G3Ps pooled together,

12个G3P放到一起，

two are siphoned off to form

两个被抽走

that energy rich six carbon glucose chain.

来形成六碳葡萄糖链的丰富能量。

The one fueling you via your breakfast. Success!

通过你的早餐加到身上。 成功！

But back on the manufacturing line,

但回到生产线，

the byproducts of this sugar production

糖生产的副产品

are swiftly assembled to recreate those six RuBPs.

迅速组装来重新组成六个RuBP。

That requires 30 carbons,

这需要30个碳，

the exact number contained by the remaining 10 G3PS.

这个精确的数字就是十个G3PS。

Now a molecular mix and match occurs.

现在发生分子混合和匹配。

Two of the G3Ps are welded together

两个G3P焊接到一起

forming a six carbon sequence.

形成一个六碳序列。

By adding a third G3P, a nine carbon chain is built.

通过添加一个第三G3P 构建成一个九碳链结构。

The first RuBP, made up of five carbons,

第一个RuBP由五个碳组成，

is cast from this,

形成后，

leaving four carbons behind.

留下了四个碳。

But there's no wastage here.

但是这里没有浪费。

Those are soldered to a fourth G3P molecule,

那些被焊接到第四个G3P分子，

making a seven carbon chain.

成了七碳链。

Added to a fifth G3P molecule,

添加到第五个G3P上，

a ten carbon chain is created,

形成了一个十碳链，

enough now to craft two more RuBPs.

这样就足够做成两个RuBPs。

With three full RuBPs recreated

当三个RuBPs被创建好

from five of the ten G3Ps,

从十个里面的五个G3P中，

simply duplicating this process

简单的重复过程

will renew the six RuBP chains

将更新六RuBP链

needed to restart the cycle again.

去重启这个循环。

So the Calvin cycle generates the precise number

所以卡尔文循环产生了 确切的数量的

of elements and processes

元素和过程

required to keep this biochemical production line

需要让这个生化产线

turning endlessly.

一直工作着。

And it's just one of the 100s of cycles

并且这仅仅是一百多个 循环中的一个

present in nature.

在自然界中。

Why so many?

为什么有那么多？

Because if biological production processes were linear,

因为如果生物生产过程 是线性的，

they wouldn't be nearly as efficient or successful

他们就不会如此的高效或成功

at using energy to manufacture the materials

在使用能源生产材料

that nature relies upon, like sugar.

自然是依赖的，就像糖。

Cycles create vital feedback loops

循环创造了重要的反馈循环

that repeatedly reuse and rebuild ingredients

重复使用和重建材料

crafting as much as possible

制作尽可能多的

out of the planet's available resources.

可用地球资源，

Such as that sugar,

就像糖，

built using raw sunlight and carbon

使用原始阳光和碳

converted in plant factories

在植物中的转换

to become the energy that powers you

形成让你强壮的能量

and keeps the cycles revolving in your own life.

从而保证你自己生活周而复始的需求。