Electron Transport Chain | Made Easy

Summary

In this video, Dr. Mike explains the electron transport chain, the final step of cellular respiration. The process starts with glucose, which undergoes glycolysis and the Krebs cycle, producing molecules like NADH and FADH2. These molecules transfer electrons to protein complexes in the mitochondria, creating a proton gradient. This gradient powers ATP synthase, generating ATP, the main energy currency of the cell. The final electron acceptor is oxygen, which combines with protons to form water as a byproduct. Dr. Mike also highlights key redox reactions and the role of various protein complexes.

Takeaways

• 🔬 The electron transport chain is the final step in cellular respiration, following glycolysis and the Krebs cycle.
• 🍬 Glucose is converted into pyruvate, then into acetyl-CoA, which enters the Krebs cycle to produce NADH and FADH2 molecules.
• 🔋 NADH and FADH2 are crucial as they carry hydrogen and electrons, which are essential for the electron transport chain.
• ⚡ The process involves the transfer of electrons through a series of protein complexes (Complex I to IV) within the mitochondria.
• 🚫 Complex I (NADH dehydrogenase) receives electrons from NADH, while Complex II (succinate dehydrogenase) receives electrons from FADH2.
• 💧 Coenzyme Q10 plays a critical role in accepting electrons from both Complex I and II, preventing oxidative stress.
• 🔁 The movement of electrons through the complexes generates a proton gradient across the mitochondrial membrane.
• 💨 Complex IV (cytochrome c oxidase) is the final acceptor of electrons, which are then passed to molecular oxygen, forming water.
• ⚙ ATP synthase uses the energy from the proton gradient to synthesize ATP, the energy currency of the cell.
• 🌟 The ultimate goal of the electron transport chain is to produce ATP, which is vital for cellular functions.

Q & A

What is the final step of cellular respiration?

The final step of cellular respiration is the electron transport chain.

What is the purpose of undergoing glycolysis, the Krebs cycle, and the electron transport chain?

The purpose of these processes is to produce NADH and FADH2 molecules, which hold onto hydrogen and electrons.

How many molecules of pyruvate are produced from one molecule of glucose during glycolysis?

Two molecules of pyruvate are produced from one molecule of glucose during glycolysis.

How many molecules of NADH are produced during the conversion of glucose to pyruvate?

Two molecules of NADH are produced during the conversion of glucose to pyruvate.

What are the two products of the conversion of pyruvate to acetyl-CoA?

The two products of the conversion of pyruvate to acetyl-CoA are two molecules of acetyl-CoA and two more molecules of NADH.

What is the role of NAD+ and FAD in the cellular respiration process?

NAD+ and FAD steal hydrogen from carbon molecules, with NAD+ creating NADH and FAD creating FADH2.

What is the function of Complex One in the electron transport chain?

Complex One receives electrons from NADH, undergoes redox reactions, and pumps protons into the intermembrane space.

What is the role of Coenzyme Q10 in the electron transport chain?

Coenzyme Q10 holds onto electrons without causing oxidative stress and passes them to Complex Three.

How does Complex Two differ from Complex One in terms of electron handling?

Complex Two receives electrons from FADH2 instead of NADH and does not pump protons across the membrane.

What is the final electron acceptor in the electron transport chain?

The final electron acceptor is molecular oxygen, which combines with electrons to form water.

What is the primary purpose of the electron transport chain?

The primary purpose of the electron transport chain is to produce ATP through the movement of protons and electrons.

Outlines

00:00

🔬 Cellular Respiration and Electron Transport Chain

Dr. Mike introduces the electron transport chain, the final stage of cellular respiration, which involves converting glucose into pyruvate, then into acetyl-CoA, and through the Krebs cycle, producing substrates that can hold hydrogen and electrons. The process generates NADH and FADH2 molecules, which are crucial for the electron transport chain. The video explains the role of NAD+ and FAD in stealing hydrogen and electrons from carbon molecules, forming NADH and FADH2. These molecules are then utilized in the mitochondria, where they are handed off to various protein complexes.

05:03

🚀 The Role of Protein Complexes in the Electron Transport Chain

The video script details the function of protein complexes in the electron transport chain. NADH passes its electrons to Complex I, which pumps hydrogen ions into the intermembrane space, creating a proton motive force. Coenzyme Q10 receives electrons from both Complex I and Complex II, preventing oxidative stress. Complex III receives electrons from Coenzyme Q10 and pumps more hydrogen ions, while Complex IV and cytochrome C pass electrons to oxygen, forming water. The process of electron transfer through these complexes is likened to a game of hot potato, emphasizing the need for the electrons to be passed quickly to avoid damage.

10:05

💧 ATP Synthesis and the Final Stages of Cellular Respiration

The final paragraph explains how the high concentration of hydrogen ions in the intermembrane space drives the synthesis of ATP through ATP synthase. The hydrogen ions move down their concentration gradient, spinning proteins that facilitate ATP production from ADP and phosphate. The paragraph concludes by emphasizing the purpose of the entire cellular respiration process: to produce ATP. The byproduct of this process is water, formed when hydrogen ions combine with oxygen. Dr. Mike wraps up by inviting viewers to engage with the content and follow him on social media for more educational videos.

Keywords

💡Electron Transport Chain

The Electron Transport Chain (ETC) is the final step of cellular respiration, where electrons from molecules like NADH and FADH2 are transferred through protein complexes embedded in the inner mitochondrial membrane. This transfer of electrons creates a proton gradient that ultimately drives ATP synthesis. The video discusses the role of the ETC in producing ATP, highlighting its importance in energy production.

💡NADH

NADH is a molecule that carries electrons and protons to the Electron Transport Chain. It is produced during earlier stages of cellular respiration, such as glycolysis and the Krebs cycle. In the video, NADH is shown to donate electrons to Complex I of the ETC, playing a key role in energy generation by creating a proton gradient necessary for ATP synthesis.

💡FADH2

FADH2 is another electron carrier, similar to NADH, that transfers electrons to the Electron Transport Chain, specifically to Complex II. The video explains that while FADH2 also helps in creating a proton gradient for ATP production, it enters the chain later than NADH, resulting in slightly less energy (ATP) production.

💡ATP

ATP (adenosine triphosphate) is the primary energy currency of the cell. It is produced as the end product of the Electron Transport Chain through ATP synthase. The video emphasizes that the entire process of glycolysis, the Krebs cycle, and the ETC is aimed at producing ATP, which powers many biological processes.

💡Proton Gradient

A proton gradient is created by the movement of protons (H+) across the inner mitochondrial membrane as electrons are transferred through the Electron Transport Chain. This gradient drives ATP synthesis by allowing protons to flow back through ATP synthase. In the video, the proton gradient is explained as the key driver of ATP production in mitochondria.

💡Complex I

Complex I is the first protein complex in the Electron Transport Chain, where NADH donates electrons. These electrons trigger a series of redox reactions, allowing protons to be pumped into the intermembrane space. The video describes how this process contributes to the proton gradient needed for ATP synthesis.

💡Complex II

Complex II is another protein complex in the Electron Transport Chain that accepts electrons from FADH2. Unlike Complex I, it does not pump protons across the membrane but still contributes to the electron transport process. The video highlights how Complex II helps in electron transfer but without contributing directly to the proton gradient.

💡Coenzyme Q10

Coenzyme Q10 is a small molecule that transfers electrons from Complex I and Complex II to Complex III in the Electron Transport Chain. It plays a crucial role in maintaining the flow of electrons and preventing oxidative stress. The video explains how Coenzyme Q10 helps protect the complexes from damage by holding electrons temporarily.

💡Cytochrome C

Cytochrome C is a small protein that carries electrons from Complex III to Complex IV in the Electron Transport Chain. It ensures the smooth transfer of electrons, preventing damage from oxidative stress. The video mentions Cytochrome C as an important intermediate that ensures electrons are passed efficiently between complexes.

💡Oxygen

Oxygen acts as the final electron acceptor in the Electron Transport Chain. It accepts electrons at Complex IV and combines with protons to form water. Without oxygen, the chain would halt, leading to a lack of ATP production. The video concludes that oxygen's role is essential as it prevents oxidative damage and allows the ETC to continue.

Highlights

Introduction to the electron transport chain as the final step of cellular respiration.

Glucose is converted into pyruvate and then into acetyl-CoA, preparing for the electron transport chain.

During glycolysis, two molecules of NADH are produced from glucose.

Conversion of pyruvate to acetyl-CoA results in two additional NADH molecules.

The Krebs cycle generates six NADH and two FADH2 molecules per glucose molecule.

NAD+ steals hydrogen to create NADH, involving a proton and an electron.

FAD steals two hydrogens to create FADH2, which hold onto electrons.

NADH and FADH2 molecules are essential for the electron transport chain.

NADH hands off its electrons to Complex I in the inner mitochondrial membrane.

Complex I uses the energy from electrons to pump protons into the intermembrane space.

Coenzyme Q10 receives electrons from Complex I and prevents oxidative stress.

Complex II steals electrons from FADH2 and passes them to Coenzyme Q10.

Complex III receives electrons from Coenzyme Q10 and pumps more protons into the intermembrane space.

Cytochrome C is an intermediate that carries electrons from Complex III to Complex IV.

Complex IV passes electrons to the final electron acceptor, oxygen, forming water as a byproduct.

ATP synthase uses the proton gradient to synthesize ATP, the ultimate goal of cellular respiration.

The process results in a significant amount of ATP production, highlighting the efficiency of the electron transport chain.

Transcripts

hi everyone Dr Mike here in this video

we're taking a look at the electron

transport chain this is the final step

of cellular respiration remember in this

process we're taking glucose turning it

into pyruvate turning into acetyl-coa

undergoing the Krebs cycle spitting out

a whole bunch of substrates that can

hold hydrogen and electrons for us and

handing them off to this particular step

let's take a look

[Music]

all right so what we need to understand

is first of all remember we took glucose

and this glucose we turned into pyruvate

in actual fact we turned it into two

molecules of pyruvate which we then

turned into two molecules of acetyl COA

all right in this process of turning

glucose to pyruvate glycolysis we spat

out two molecules of something called

NAD H in the process of turning pyruvate

to acetyl-cole we spat out two more

molecules of NAD

H and when acetylchawaii entered the

mitochondria and entered what we call

the crabs cycle also known as the citric

acid cycle also known as the

tricarboxylic acid cycle we spat out six

nadh

and we spat out two

f a d h

two this is the whole purpose of us

undergoing these extensive processes is

to spit out these nadh molecules and

fadh2 molecules why to recap if you

haven't watched my glycolysis or Krebs

video remember this

the whole purpose is for NAD Plus or

f a d to steal hydrogen from these

carbon molecules and with that hydrogen

steel electrons so at the end of the day

the NAD plus stole two hydrogens

to create n a d h

right plus another h and a hydrogen ion

what does this mean basically the NAD

plus stole a full complete hydrogen

remember hydrogen is just a positive

proton with a negative electron flying

around the outside NAD plus stole one of

these to give us nadh plus Let's ignore

this for the moment then it stole

another hydrogen but only stole the

electron

so getting rid of that and keeping or

what's remaining is a positive proton

and another way of writing a positive

proton is h plus so that's what NAD plus

does still two hydrogen one it keeps

everything on the second one it just

keeps the electron and releases the

proton what FID does is actually just

takes two hydrogen and creates

fadh2 so these hydrogens hold on to

electrons so what we need to have a look

at is what do they now do with them

simple they inside the mitochondria here

hand them off to a range of proteins now

here inside the mitochondria we've got

six nadh two fadh2 all have come from

one glucose the two nadh and the two

nodh here they end up entering the

mitochondria through one way or another

and then they end up here so basically

my point is we've got a whole bunch of

nadh sitting in the mitochondria and a

whole bunch of fadh two what now happens

well firstly the nadh will come across

this protein complex embedded across the

inner membrane of the mitochondria it's

an integral protein which means it spans

the complete inner membrane and so this

is called complex one

and what nadh does is it hands it off

its electrons

like this hands it off the electrons and

releases

the protons

so hence the electrons and releases the

protons

right

now what happens is in this protein

complex a number of what we call redox

steps occur what is this all right

redox means reduction and oxidation

they're two totally separate the flip

side of a coin right remember this

l a o Leo the loss of electrons is

oxidation so when a molecule loses an

electron it's called oxidation when a

molecule gains electrons it's called

reduction so simply what happens in here

is that the electron is passed from one

molecule to another molecule and as it

does this this is redox right one gains

and it loses and it gains and it loses

and in this it excites this protein

complex it excites it enough that this

into this channel here can actually take

the hydrogen and pump it across into the

inter membrane space

that's step one

nadh hands off the electrons excites

complex one enough so that it can

generate a proton motive Force to pump

the hydrogens across into this inter

membrane space the thing is this complex

cannot hold on to the electron because

or electrons because it will damage it

electrons if it's been stripped or added

to something can cause oxidative stress

this protein is not equipped to handle

electrons long term it will be subject

to oxidative stress so it must hand this

electron off and it hands it off to this

thing here this is called coenzyme Q10

coenzyme Q10 and what coenzyme Q10 does

is it is equipped to hold on to the

electron without causing oxidative

stress

perfect next thing is this this is now

complex two this was complex one this is

complex two complex two does not steal

electrons from nadh but it does still

electrons from fadh2

producing fad similar thing the electron

jumps in and a whole bunch of redox

steps occur which ends up exciting this

particular protein but

there is no trans membrane

channel for the hydrogen to be pumped

across because it's got the coenzyme Q10

hat on it

there's no room for it to move through

so it excites it but ultimately its job

was just to steal the electrons from

fadh2 and again passes it off to

coenzyme Q10 because just like complex

one complex two can't hold on to it so

it passes it off all right now coenzyme

Q10 has these electrons what it will do

is it'll pass these electrons off

to complex three

same things happening it excites complex

three through a bunch of redox reactions

and in doing so

creates this proton motive Force because

remember fadh2 gave the electrons to

complex two but released the hydrogen

ions

similar to nadh releasing hydrogen ions

but complex ones pumping them up not

complex two but complex three is also

pumping them up into the inter membrane

space so we're starting to really

accumulate these hydrogen ions in this

inter membrane space again complex three

can't hold on to electrons it will

damage it it must pass it off to an

intermediate that can that's this thing

here called cytochrome C it will take

these electrons and look after it for

the time being

now cytochrome C passes the electrons

off

to complex four

it plays hot potato with the electrons

or these redox reactions occur

exciting it and that

excites this Channel or I should say

this pump to pump the hydrogen ions

across into the inter-membrane space

what's happened so far so far complex

one three and four have pumped hydrogen

ions across into the inter-membrane

space because they've been excited by

playing hot potato with electrons these

electrons cannot stay in any of these

complexes so they need to hand it off to

something that's equipped to deal with

it that won't cause oxidative stress

that's coenzyme Q10 it helps reduce

oxidative stress and that cytochrome C

helps reduce oxidative stress

but what I've just said is that it can't

hold on to electrons what happens to

complex four there's no more

intermediates for it to pass electrons

too so what it hands it off to is what

we call the final electron acceptor or

The Terminal electron acceptor which is

oxygen so we've got oxygen here

which they select these electrons are

passed off to

and in doing so it splits that oxygen

like that

O Negative

what happens well we've got O Negative

here and we've got some hydrogen ions in

here as well they bind together to form

water

we produce water as a byproduct of this

but you're probably saying but all the

hydrogen ions are pumped across there's

nothing for water to bind to well let's

now take a look at the final step this

is an ATP synthase this thing creates

ATP it's the whole purpose of glycolysis

Krebs cycle electron transport chain

it's all about this what happens is this

High concentration of hydrogen ions in

the inter membrane space of the

mitochondria they want to go down their

concentration gradient and they do so

through this Channel and as it moves

through the energy that's released from

going down its concentration gradient

spins these particular proteins

physically spins them

and the spinning of these proteins

allows for ATP to be synthesized we take

ADP and we take phosphate and we end up

creating a huge amount

of ATP that's the final product and

again the hydrogen that then gets pumped

back into the inner workings of the

mitochondria will fuse or bind I should

say with this molecular oxygen which is

now negatively charged and produce water

and that water is the byproduct so the

whole purpose of this is to produce all

this ATP

that's the whole purpose and it's

because through this process we have

created nadh molecules and fadh2

molecules they hold onto hydrogen hold

on to electrons which get passed through

the electron transport chain and at the

end of it we produce an amazing amount

of ATP

hi everyone Dr Mike here if you enjoyed

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