or the fats. The fat that's found in butter or the fat that's found in olive oil is what

俗稱脂肪。 那些存在於奶油、橄欖油當中的脂肪，

we call a triglyceride. It's basically going to have a head, a glycerol head and then it'g

我們稱之「三酸甘油酯」。它的基本組成為一個甘油分子的頭端，

going to have three fatty acids tails. And that's where the energy is. And so when we

以及三個脂肪酸分子的尾端－－此即能量所在。 因此當我們攝取脂肪，

eat fat we can break it down. We have enzymes called lipases that are able to break that

體內有種稱為「脂酶」的酵素，能夠把它分解下來，

down and then we can get energy from it. And that's been very important. We can store energy

人體便可從中獲取能量。這是非常重要的：我們可以把能量儲存在

in fats inside our body and then we can burn them when we need them. But don't forget that

體內的脂肪，當我們需要的時候，再燃燒它汲取能量。 但是別忘記，

fats in addition to providing energy also provide the surroundings. And so the cell

除了提供能量，脂肪也提供了......遮蔽的功能，

membrane that goes around every cell is made up of phospholipids. And the cholesterol is

那些環繞著每一個細胞的膜，都是由「磷脂質」所構成。

found within the phospholipid by layer and that maintains the fluidity of the cell. And

而磷脂雙層內發現的「膽固醇」則維持了細胞的流動性。由此看來，

so lipids are incredibly important. But where does the energy come from? That comes from

脂質的重要性是不言而喻的。 那麼，能量又是從何而來？脂質的能量源自於

the hydrocarbons. And so if you look at those fatty acid tails it's essentially a carbon

「碳氫化合物」。如果你觀察這些脂肪酸的尾端， 它本質上是一個碳原子

attached to a carbon to a carbon to a carbon to a carbon . . . and then it has hydrogen

連接到另一個碳原子，連接到另一個碳原子（x24次）......以及

around the outside of it. And so we call that a hydrocarbon. And there's energy in those

在碳鏈外的氫原子所組成，故名「碳氫化合物」。 能量便存在於這些鍵結當中。

bonds. And so gasoline burning out of control or the paraffin wax that's burning in a candle

無論是劇烈燃燒的汽油，或燃燒石蠟的蠟燭

is a hydrocarbon. There's a lot of energy between those carbon hydrogen bonds. And so

皆為碳氫化合物。這些碳氫鍵之間存在著的很多能量。

there's also a lot of energy found in butter or in olive oil. It's in the bonds between

奶油或橄欖油當中的碳氫化合物亦然－－能量存乎於

the carbon and the hydrogen. And so let's start with a triglyceride. So this is a basic

碳和氫之間的鍵結當中。 讓我們從三酸甘油酯開始，這是一個基本的脂肪。

fat. The head up here is going to be called the glycerol head and then this is going to

分子的頭部，這部份被稱為甘油頭端，而另一邊

be the fatty acid tails that go down the end. And so fatty acid tail has so much carbon

則是一路延伸到底的脂肪酸尾端。 我們可以看到，脂肪酸尾端的碳氫原子數目

and hydrogen in it that on this diagram we don't even draw them. Each of these points

是如此之多，多到這張圖甚至不把它們詳示。 這些長鏈中的每一個的點

represents a carbon, a carbon, a carbon. And then right here we're going to have two hydrogen

皆代表一個個的碳原子。而在這長碳鏈附近，

bonds or two hydrogens bonded to each of those carbons. And so you can see that there's a

每個碳原子還會被兩個氫原子鍵結。由此可見，

huge amount of energy locked within that triglyceride and we can get that out through cellular respiration.

大量的能量被封存在這一分子的三酸甘油酯當中， 而藉由細胞呼吸作用，我們得以汲取這些能量。

But know this. Those tails can come in two different forms. We can have what are called

請注意，這些尾巴可能存在兩種不同的形式。

saturated tails. A saturated tail is going to have hydrogen all the way around the outside.

一種可能是脂肪酸為飽和狀態， 飽和脂肪酸上的氫原子佈滿了碳鏈的周圍。

And if you have hydrogen all the way around the outside then you're going to be saturated

想像如果你被一堆氫原子所包圍，

with hydrogen. And if you're a saturated fat you're going to be a straight fat. And so

那麼你便被這些氫原子所「飽和」。 而如果你是個飽和脂肪，那麼你將會是直鏈的脂肪。

a triglyceride is going to have three of these fatty acid tails and the glycerol head, but

所以三酸甘油酯分子 會有三個這些脂肪酸的尾巴，一個頭端的甘油，

if it is saturated all of those are going to be straight. And if they're all straight

如果它們都是飽和的，那麼三條尾巴都將會是直鏈的。 而如果它們都是直鏈的，

they can pack up on top of other triglycerides. And so saturated fats are normally going to

這些尾巴便能夠，與其他的三酸甘油酯擠在一起。 因此，飽和脂肪通常

be a solid at room temperature. What happens if you don't have hydrogen all the way around

在室溫下是固體。而如果你尾巴的碳鏈 並沒有完全被氫原子所包埋，會發生什麼事呢？

the outside? You're going to form these double bonds in here. If you have double bonds basically

這種情況下，碳鏈將會形成雙鍵，像這裡畫的。

what that does is it puts a bend in your tail. And so you're going to have a kinky tail.

雙鍵基本上會在你脂肪酸的碳鏈上，造成一個扭折， 你將會有一個彎折的尾巴。

And so if you're a saturated fat, you're going to look like this. If you're an unsaturated

如果你是一個飽和脂肪，你看起來會像這樣。 如果你是一個不飽和脂肪

fat you're going to look like this with kinky tails. And the kinky tails can't quite pack

你看起來則會像的這樣－－有彎折的尾巴。 而這些彎折的尾巴不太能夠擠在一起。

together. And so normally fats that are unsaturated are going to be a liquid at room temperature.

因此，通常不飽和的脂肪在室溫下會是液體。

Now humans have figured out how to take, for example, vegetable oil, which is a unsaturated

現今，人類已經理解如何能夠把，舉例來說， 植物油，一種不飽和脂肪，

fat or it's going to be a liquid at room temperature and we can bubble hydrogen through it. We

或者其它任何在室溫下為液體的脂肪， 通以氫氣氣泡，

can straighten out those tails and we can make a saturated fat called margarine that's

使它們的尾巴變成直鏈，人為地製造出飽和脂肪， 也就是「人造奶油」，

going to be a solid at room temperature. We've transformed this fat and if you know anything

而它在室溫下將會是固體－－我們改造了這個脂肪！ 如果你對所謂脂肪稍有認識的話，

about fats those saturated fats are the ones that are least best for us and can lead to

那些飽和脂肪，這類對我們身體最不好的脂肪，

arteriolosclerosis, especially trans fats. Example then of how we've tried to get around

會導致小動脉硬化，特別是反式脂肪。 有個例子展示了我們如何試圖克服

this. And this is a somewhat funny story. This is olestra. Olestra is a fat that was

這個缺點，這是個滿有趣的故事： Olestra 是一種由人造的脂肪，

made by humans. And so basically what they did us took a normal triglyceride but they

基本上，人類所動的手腳是， 他們把尋常的三酸甘油酯分子，

built it around a sucrose, so they built it around a sugar. And so instead of having just

接到一蔗糖分子的周圍，製造了一個由脂質環繞的糖。 不同於尋常的三酸甘油酯，

three of these fatty acid tails they had sometimes eight, sometimes ten. Sometimes even more.

其尾巴不會只有三條， 它們可能有八條、十條，有時甚至更多。

What's neat about that is that when you go through your digestive system we don't have

這個分子特別的是，在消化系統中，我們並沒有

olestrase. We don't have an enzyme that can break that down and so the olestra moves right

所謂的「olestrase」。 我們沒有任何酵素可以分解它，所以 olestra 便持續

through our digestive system. So it's a fat that feels like a fat, tastes like a fat but

完好無缺地通過我們的消化系統。因此， 它算是一種看起來像脂肪，嚐起來像脂肪，

it doesn't make us fat. And so Wow chips were introduced I think in the 1990s and had this

但卻不會使我們發胖的脂肪。 我記得，大約在九零年代問世的 Wow 洋芋片，其成分

olestra in it. Basically what happened is when people started eating these Wow chips,

就含有 olestra 然而吃了這些洋芋片的人，

they got incredibly sick. They got cramping and they had to put a warning label on the

卻生了嚴重的病。除了痙攣， 他們甚至在包裝外標記了警語表示

outside that it can lead to loose stools, and it pulls vitamins outside of your body.

它可能導致脂肪痢，還會造成維生素從體內流失。

They've kind of refined this since then and so there's not a lot of these adverse reactions.

之後，他們已稍加精鍊含有此成分的產品， 於是現在便較少聽到，食用後發生的這些不良反應。

I think Pringles light chips still contain olestra in it, but we're tricking our body,

我想，品客洋芋片現在仍含有 olestra 但實際上我們在欺騙我們的身體，

because our body doesn't have those enzymes. Now I also said there are two more important

因為我們的身體並沒有分解它的酵素。 剛才我也提及了另外兩種比較重要的脂質

lipids. The first one's called phospholipids. Phospholipids are going to have, you can see,

第一種稱為磷脂質。 磷脂質的分子具有，你可以看到，

two fatty acid tails, but they're going to have a head that contains a phosphate group.

兩個脂肪酸的尾巴， 除此之外，還具有一個含磷酸基團頭端。

That phosphate group is going to have a negative charge. And so normally if we were to pour

這個磷酸基團帶有一個負電荷。因此一般而言，

oil into water it's going to separate. And the reason why is that fats are non polar.

如果我們把油倒入水中，它們會分開。因為脂肪是非極性的，

They don't have a charge. But what's neat about phospholipids is that they have a head

它們並不具有電荷。但對磷脂質而言有趣的是，他們有個

that is going to have a negative charge and then they have the tails that are uncharged.

帶有一個負電荷的頭端，以及不帶電的尾端。

And so if you just throw a bunch of phospholipids in water they'll form these spheres, micelles,

所以，如果你若是把一堆的磷脂質倒進水中， 他們將會形成這些球狀物、微胞，

or they'll form these spontaneous membranes. And so the cell membranes of all cells are

又或者他們會自發性地形成這些膜。所以說，所有細胞的細胞膜

made up of phospholipids. And so bacteria, archaea, eukarya, plants, animals, fungi,

皆是由磷脂質所構成。 諸如細菌，古細菌，真核生物，植物，動物，真菌......

we all have cell membranes. And those membranes are made up of phospholipids. They regulate

皆擁有細胞膜。而這些膜都是由磷脂質構成的。他們調節了

what gets in and out a cell. Cholesterol is going to maintain the fluidity of the membrane.

哪些物質能夠進出細胞。 膽固醇則是要保持膜的流動性，

And so this cell membrane right here is made up of phospholipids. Those phospholipids are

這兒看到的是磷脂質組成的細胞膜。這些磷脂質會

constantly moving back and forth and that's important because it allows things like oxygen

不斷地來回運動，這點非常重要，因為這使得氧氣能夠進入

to get in and carbon dioxide to get out. But if the cell gets heated up those phospholipids

二氧化碳能夠離開。 但是，如果細胞處在溫度高的狀態，

tend to fall apart. And if it get's really cold they'll crowd together and so the function

這些磷脂質會傾向分崩離析。 而如果溫度過低，他們則會聚集在一起，

of cholesterol is to grab onto those fatty acid tails and hold them together when it

因此膽固醇的功能，乃在於抓住這些脂肪酸的尾巴，

gets too cold but keep them apart . . . or hold them together when they get to warm and

溫度過高的時候，將他們約束在一起；

keep them apart when they get too cold. And so cholesterol is important at maintaining

溫度過低的時候，則讓他們彼此維持距離。 所以說膽固醇的重要性，在於保持

that integrity of the cell membrane. And you can see cholesterol in this diagram right

細胞膜的完整性。在這個圖示當中， 你也可以看到在這兒的膽固醇分子。

here. We can build it in each of our cells and we have to build it in our cells, but

體內的每個細胞都能夠製造膽固醇， 實際上我們也必須製造它，

we have to get a little bit of it in our diet. And so we need lipids in our diet. If we don't

但從食物當中，我們仍需攝取少量的膽固醇。 脂質是我們飲食所必需的。如果我們缺乏脂質

have lipids we can't get energy and more importantly we can't make our cell membranes. However,

我們便不能從中得到能量， 更重要的是，我們將無法製造的細胞膜。然而，

today everybody's getting the fat they need. This is my favorite place to eat when I go

當今，大家攝取脂肪的都已足夠。 這是我去加州的時候

to California because we don't have them in Montana. This is In-N-Out burger. I love the

最喜歡去用餐的地方，因為我住的蒙大拿州，境內並沒有這家店。 這個地方是 In-N-Out burger，

taste of a big burger from In-N-Out. The lipids are great but there's probably too much trans

我超喜歡 In-N-Out 大漢堡的味道－－ 脂質是真的很不錯，但其中可能含有太多的反式脂肪。

fats in there. It's not good for me and could lead to heart disease. But for now I'm going

這是對我並不好，可能會導致心臟疾病。不過目前我還是會繼續享用。

to keep eating them. So that's lipids, that's fat and I hope that was helpful.

以上是脂質的介紹，希望對各位有所幫助。