After being done with glycolysis and the Krebs
0:02
Cycle, we're left with 10 NADHs and 2 FADH2s.
0:10
0:12
And I told you that these are going to be used in the
0:15
electron transport chain.
0:16
And they're all sitting in the matrix of our mitochondria.
0:19
And I said they're going to be used in the electron transport
0:20
chain in order to actually generate ATP.
0:26
So that's what I'm going to focus on in this video.
0:28
The electron transport chain.
0:30
0:37
And just so you know, a lot of this stuff is known.
0:41
But some of the details are actually
0:42
current areas of research.
0:44
People have models and they're trying to
0:45
substantiate the models.
0:46
But things are happening at such a small scale here that
0:50
people can just look at the evidence, some of which is
0:52
indirect, and say, this is probably what's happening.
0:54
Most of this is very well established, but some of the
0:57
exact mechanisms-- for example, how exactly some of
1:02
the proteins work-- aren't completely understood.
1:05
So I think it's very important for you to understand that
1:08
this is at the cutting edge, that you're already there.
1:11
So the basic idea here is that the NADHs-- and that's where
1:15
I'll focus.
1:15
FADH2 is kind of the same idea.
1:17
Although its electrons are just at slightly
1:19
lower energy state.
1:21
So they won't produce quite as many ATPs.
1:23
Each NADH is going to be-- as you'll see-- indirectly
1:32
responsible for the production of three ATPs.
1:36
And each FADH2, in a very efficient cell, in both of
1:42
these cases, will be indirectly responsible for the
1:44
production of two ATPs.
1:48
And the reason why this guy produces fewer ATPs is because
1:52
the electrons that he has going into the electron
1:55
transport chain are at a slightly lower energy level
1:58
than the ones from NADH.
2:00
So in general, I just said indirectly.
2:02
How does this whole business work?
2:04
Well in general, NADH, when it gets oxidized-- remember,
2:11
oxidation is the losing of electrons or the losing of
2:14
hydrogens that happen to have electrons.
2:17
We can write its half reaction like this.
2:19
Its oxidation reaction like this.
2:21
You'll have some NAD plus, which you can then go and use
2:25
back in the Krebs Cycle and in glycolysis.
2:29
You have some NAD plus, you'll have a proton, a positive
2:33
hydrogen ion is just a proton.
2:35
And then you'll have two electrons.
2:38
This is the oxidation of NADH.
2:39
2:44
It's losing these two electrons.
2:46
Oxidation is losing electrons.
2:48
OIL RIG.
2:49
Oxidation is losing electrons.
2:51
Or you can imagine it's losing hydrogens, from which it can
2:54
hog electrons.
2:55
Either one of those is the case.
2:57
Now this is really the first step of the
2:59
electron transport chain.
3:00
These electrons are transported out of the NADH.
3:05
Now, the last step of the electron transport chain is
3:08
you have two electrons-- and you could view it as the same
3:12
two electrons if you like-- two electrons plus two
3:16
hydrogen protons.
3:17
And obviously if you just add these two together, you're
3:20
just going to have two hydrogen atoms, which is just
3:22
a proton and an electron.
3:24
Plus one oxygen atom, so I could say one half of
3:28
molecular oxygen.
3:29
That's the same thing as saying one oxygen atom.
3:32
And you're going to produce-- if I have one oxygen and two
3:35
complete hydrogens, I'm left with water.
3:37
3:39
And you could view this, we're adding electron or we're
3:42
gaining electrons to oxygen.
3:44
OIL RIG.
3:45
Reduction is gaining electrons.
3:48
So this is the reduction of oxygen to water.
3:54
This is the oxidation of NADH to NAD plus.
3:59
Now, these electrons that are popping out of-- these
4:02
electrons right here-- that are popping out of this NADH.
4:06
And when they're in NADH they're at a
4:08
very high energy state.
4:11
And what happens over the course of the electron
4:13
transport chain is that these electrons get transported to a
4:17
series of, I guess you could call
4:18
them transition molecules.
4:20
But these transition molecules, as the electrons go
4:22
from one to the other, they go into slightly
4:24
lower energy states.
4:26
And I won't even go into the details of these molecules.
4:28
One is coenzyme Q, and cytochrome C.
4:33
4:36
And then they eventually end up right here and they are
4:38
used to reduce your oxygen into water.
4:43
Now every time an electron goes from a higher energy
4:46
state to a lower energy state-- and that's what it's
4:48
doing over the course of this electron transport chain--
4:52
it's releasing energy.
4:53
5:00
So energy is released when you go from a higher state to a
5:02
lower state.
5:03
When these electrons were in NADH, they were at a higher
5:06
state than they are when they bond to coenzyme Q.
5:09
So they release energy.
5:11
Then they go to cytochrome C and release energy.
5:13
Now that energy is used to pump protons across the
5:17
cristae across the inner membrane of the mitochondria.
5:20
And I know this is all very complicated sounding.
5:22
And this is the cutting edge.
5:25
So it maybe should sound a little complicated.
5:27
Let me draw a mitochondria.
5:30
So let me draw a small mitochondria just so you know
5:33
where we're operating.
5:34
That's its outer membrane.
5:36
And then its inner membrane, or its cristae,
5:38
would look like that.
5:40
5:45
And let me zoom in on the membrane.
5:47
So let's say if I were to zoom in right there.
5:52
So if I were to zoom that out, that box would look like this.
5:54
You have your crista here.
5:57
And I'm going to draw it thick.
6:00
So I'm zooming in.
6:01
This green line right here, I'm going to
6:02
draw it really thick.
6:03
I'm going to color it in with the green, just like that.
6:06
And then you have your outer membrane.
6:09
This outer membrane, I can do it up here.
6:12
And I'll just color it in.
6:13
You don't even have to see the outside of the outer membrane.
6:16
Right here, this space right here, this is the outer
6:18
compartment.
6:20
And then we learned in the last video, this space right
6:23
here is the matrix.
6:24
6:27
This is where our Krebs cycle occurred.
6:29
And where a lot of our NADH, or really all of
6:31
our NADH, is sitting.
6:33
So what happens is, every time NADH gets oxidized to NAD
6:37
plus, and the electrons keep transferring from one molecule
6:41
to another, it's occurring in these big protein complexes.
6:44
And I'm not going to go into the details on this.
6:46
So each of these protein complexes span-- so let's say
6:51
that's a protein complex where this first oxidation reaction
6:55
is occurring and releasing energy.
6:58
And then let's say there's another protein complex here,
7:00
where the second oxidation reaction is occurring and
7:03
releasing energy.
7:04
And these proteins are able to use that energy to essentially
7:09
pump-- this might all seem very complicated-- to
7:12
essentially pump hydrogens into the outer membrane.
7:16
It actually pumps hydrogen protons.
7:19
And let me be very clear.
7:19
Hydrogen protons into the outer membrane.
7:24
And every one of these reactions pump out a certain
7:27
number of hydrogen protons.
7:29
So by the end of the electron transport chain, or if we just
7:32
followed one set of electrons, by the time that they've gone
7:35
from their high energy state in NADH to their lower energy
7:40
state in water, by the time they've done that, they've
7:44
supplied the energy to these protein complexes that span
7:48
our cristae to pump hydrogen from the matrix
7:53
into the outer membrane.
7:55
So really the only byproduct of the oxidation of NADH into,
8:00
eventually, water, or the oxidation of NADH and the
8:04
reduction of oxygen into water, isn't ATPs yet.
8:08
It's just this gradient where we have a lot higher hydrogen
8:11
proton concentration in the outer compartment than we do
8:16
in the matrix.
8:17
Or you could say that the outer compartment becomes a
8:19
lot more acidic.
8:20
Remember acidity is just hydrogen proton concentration,
8:23
the concentration of hydrogen protons.
8:26
So the byproduct of all of this energy is used to really
8:29
just pump these protons into the outer membrane.
8:32
So you have two things.
8:33
The outer membrane becomes more acidic
8:37
than the matrix inside.
8:38
Maybe we could call that basic.
8:40
And obviously these are all positively charged particles.
8:42
So there's actually an electric gradient, an electric
8:48
potential between the outer membrane
8:50
and the inner membrane.
8:51
This becomes slightly negative, that becomes
8:53
slightly positive.
8:54
These guys wouldn't naturally do this on their own.
8:56
If this is already acidic and it's already positive, left to
9:00
its own devices, these more protons wouldn't be entering.
9:02
And the energy to do that is supplied by electrons going
9:06
from high energy state in NADH to going to a lower energy
9:11
state, eventually, on the oxygen in the water.
9:14
That's what's happening.
9:15
But essentially all that's happening is protons being
9:18
pumped from the matrix into the outer compartment.
9:22
Now once that gradient forms, these guys
9:24
want to get back in.
9:26
These guys want to get back into the matrix.
9:29
And that is where the ATPs are formed.
9:32
So there's a protein that also spans this.
9:36
Let me draw.
9:37
Remember this is all this inner membrane right here.
9:40
Let me just draw it a little bit bigger right here.
9:42
So that's our inner membrane, our cristae right there.
9:47
There's a special protein called-- and I'll show you
9:51
actually a better diagram of what looks like in a second--
9:54
called ATP synthase.
9:56
10:04
And what happens is, remember because of the electron
10:07
transport chain, we have all of these hydrogen ions up
10:09
here, all of these protons really.
10:12
All they are is a proton.
10:13
That really want to get back into the matrix down here.
10:18
10:21
But they c
หลังจากทำการ glycolysis และเครบส์0:02วงจร เรากำลังทิ้ง 10 NADHs และ 2 FADH2s0:100:12และฉันบอกคุณว่า เหล่านี้จะใช้ในการ0:15ลูกโซ่ขนส่งอิเล็กตรอน0:16และพวกเขาทั้งหมดนั่งในเมตริกซ์ของ mitochondria ของเรา0:19ผมว่าพวกเขากำลังที่จะใช้ในการขนส่งอิเล็กตรอน0:20ห่วงโซ่เพื่อสร้าง ATP0:26เพื่อ ที่ว่าอะไรฉันจะโฟกัสบนในวิดีโอนี้0:28ลูกโซ่ขนส่งอิเล็กตรอน0:300:37และเพียงเพื่อให้คุณทราบ เป็นที่รู้จักของสิ่งนี้0:41แต่บางรายละเอียดจริง0:42ปัจจุบันสาขางานวิจัย0:44คนมีรูปแบบ และพวกเขาพยายาม0:45substantiate แบบจำลอง0:46แต่สิ่งเกิดขึ้นที่นั้นมีขนาดเล็กที่นี่ที่0:50คนสามารถดูที่หลักฐาน ซึ่งเป็นเพียง0:52อ้อม และว่า นี้อาจเป็นสิ่งที่เกิดขึ้น0:54ทั้งนี้ดีก่อตั้ง แต่บาง0:57แน่นอนกลไก - ตัวอย่าง วิธีตรงบาง1:02ผลิตโปรตีน - ไม่เข้าใจ1:05ดังนั้นผมคิดว่า เป็นสิ่งสำคัญมากสำหรับคุณที่จะเข้าใจว่า1:08อยู่ที่การตัดขอบ ที่คุณได้มี1:11ดังนั้นความคิดพื้นฐานที่นี่คือ NADHs - และถูก1:15ผมจะเน้น1:15FADH2 มีชนิดของความคิดเดียวกัน1:17แม้ว่าของอิเล็กตรอนเพียงเล็กน้อย1:19สถานะพลังงานต่ำ1:21ดังนั้น พวกเขาจะไม่ผลิต ATPs ค่อนข้างมาก1:23แต่ละ NADH เป็นไปได้ - เป็นคุณจะเห็น - อ้อม1:32responsible for the production of three ATPs.1:36And each FADH2, in a very efficient cell, in both of1:42these cases, will be indirectly responsible for the1:44production of two ATPs.1:48And the reason why this guy produces fewer ATPs is because1:52the electrons that he has going into the electron1:55transport chain are at a slightly lower energy level1:58than the ones from NADH.2:00So in general, I just said indirectly.2:02How does this whole business work?2:04Well in general, NADH, when it gets oxidized-- remember,2:11oxidation is the losing of electrons or the losing of2:14hydrogens that happen to have electrons.2:17We can write its half reaction like this.2:19Its oxidation reaction like this.2:21You'll have some NAD plus, which you can then go and use2:25back in the Krebs Cycle and in glycolysis.2:29You have some NAD plus, you'll have a proton, a positive2:33hydrogen ion is just a proton.2:35And then you'll have two electrons.2:38This is the oxidation of NADH.2:392:44It's losing these two electrons.2:46Oxidation is losing electrons.2:48OIL RIG.2:49Oxidation is losing electrons.2:51Or you can imagine it's losing hydrogens, from which it can2:54hog electrons.2:55Either one of those is the case.2:57Now this is really the first step of the2:59electron transport chain.3:00These electrons are transported out of the NADH.3:05Now, the last step of the electron transport chain is3:08you have two electrons-- and you could view it as the same3:12two electrons if you like-- two electrons plus two3:16hydrogen protons.3:17And obviously if you just add these two together, you're3:20just going to have two hydrogen atoms, which is just3:22a proton and an electron.3:24Plus one oxygen atom, so I could say one half of3:28molecular oxygen.3:29That's the same thing as saying one oxygen atom.3:32And you're going to produce-- if I have one oxygen and two3:35complete hydrogens, I'm left with water.3:373:39And you could view this, we're adding electron or we're3:42gaining electrons to oxygen.3:44OIL RIG.3:45Reduction is gaining electrons.3:48So this is the reduction of oxygen to water.3:54This is the oxidation of NADH to NAD plus.3:59Now, these electrons that are popping out of-- these4:02electrons right here-- that are popping out of this NADH.4:06And when they're in NADH they're at a4:08very high energy state.4:11And what happens over the course of the electron4:13transport chain is that these electrons get transported to a4:17series of, I guess you could call4:18them transition molecules.4:20But these transition molecules, as the electrons go4:22from one to the other, they go into slightly4:24lower energy states.4:26And I won't even go into the details of these molecules.4:28One is coenzyme Q, and cytochrome C.4:334:36And then they eventually end up right here and they are4:38used to reduce your oxygen into water.4:43Now every time an electron goes from a higher energy4:46state to a lower energy state-- and that's what it's4:48doing over the course of this electron transport chain--4:52it's releasing energy.4:535:00So energy is released when you go from a higher state to a5:02lower state.5:03When these electrons were in NADH, they were at a higher5:06state than they are when they bond to coenzyme Q.5:09So they release energy.5:11Then they go to cytochrome C and release energy.5:13Now that energy is used to pump protons across the5:17cristae across the inner membrane of the mitochondria.5:20And I know this is all very complicated sounding.5:22And this is the cutting edge.5:25So it maybe should sound a little complicated.5:27Let me draw a mitochondria.5:30So let me draw a small mitochondria just so you know5:33where we're operating.5:34That's its outer membrane.5:36And then its inner membrane, or its cristae,5:38would look like that.5:405:45And let me zoom in on the membrane.5:47So let's say if I were to zoom in right there.5:52So if I were to zoom that out, that box would look like this.5:54You have your crista here.5:57And I'm going to draw it thick.6:00So I'm zooming in.6:01This green line right here, I'm going to6:02draw it really thick.6:03I'm going to color it in with the green, just like that.6:06And then you have your outer membrane.6:09This outer membrane, I can do it up here.6:12And I'll just color it in.6:13You don't even have to see the outside of the outer membrane.6:16Right here, this space right here, this is the outer6:18compartment.6:20And then we learned in the last video, this space right6:23here is the matrix.6:246:27This is where our Krebs cycle occurred.6:29And where a lot of our NADH, or really all of6:31our NADH, is sitting.6:33So what happens is, every time NADH gets oxidized to NAD6:37plus, and the electrons keep transferring from one molecule6:41to another, it's occurring in these big protein complexes.6:44And I'm not going to go into the details on this.6:46So each of these protein complexes span-- so let's say6:51that's a protein complex where this first oxidation reaction6:55is occurring and releasing energy.6:58And then let's say there's another protein complex here,7:00where the second oxidation reaction is occurring and7:03releasing energy.7:04And these proteins are able to use that energy to essentially7:09pump-- this might all seem very complicated-- to7:12essentially pump hydrogens into the outer membrane.7:16It actually pumps hydrogen protons.7:19And let me be very clear.7:19Hydrogen protons into the outer membrane.7:24And every one of these reactions pump out a certain7:27number of hydrogen protons.7:29So by the end of the electron transport chain, or if we just7:32followed one set of electrons, by the time that they've gone7:35from their high energy state in NADH to their lower energy7:40state in water, by the time they've done that, they've7:44supplied the energy to these protein complexes that span7:48our cristae to pump hydrogen from the matrix7:53into the outer membrane.7:55So really the only byproduct of the oxidation of NADH into,8:00eventually, water, or the oxidation of NADH and the8:04reduction of oxygen into water, isn't ATPs yet.8:08It's just this gradient where we have a lot higher hydrogen8:11proton concentration in the outer compartment than we do8:16in the matrix.8:17Or you could say that the outer compartment becomes a8:19lot more acidic.8:20Remember acidity is just hydrogen proton concentration,8:23the concentration of hydrogen protons.8:26So the byproduct of all of this energy is used to really8:29just pump these protons into the outer membrane.8:32So you have two things.8:33The outer membrane becomes more acidic8:37than the matrix inside.8:38Maybe we could call that basic.8:40And obviously these are all positively charged particles.8:42So there's actually an electric gradient, an electric8:48potential between the outer membrane8:50and the inner membrane.8:51This becomes slightly negative, that becomes8:53slightly positive.8:54These guys wouldn't naturally do this on their own.8:56If this is already acidic and it's already positive, left to9:00its own devices, these more protons wouldn't be entering.9:02And the energy to do that is supplied by electrons going9:06from high energy state in NADH to going to a lower energy9:11state, eventually, on the oxygen in the water.9:14That's what's happening.9:15But essentially all that's happening is protons being9:18pumped from the matrix into the outer compartment.9:22Now once that gradient forms, these guys9:24want to get back in.9:26These guys want to get back into the matrix.9:29And that is where the ATPs are formed.9:32So there's a protein that also spans this.9:36Let me draw.9:37Remember this is all this inner membrane right here.9:40Let me just draw it a little bit bigger right here.9:42So that's our inner membrane, our cristae right there.9:47There's a special protein called-- and I'll show you9:51actually a better diagram of what looks like in a second--9:54called ATP synthase.9:5610:04And what happens is, remember because of the electron10:07transport chain, we have all of these hydrogen ions up10:09here, all of these protons really.10:12All they are is a proton.10:13That really want to get back into the matrix down here.10:1810:21But they c
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