A musical explanation of the mitochondrial electron transport chain, and how it produces ATP.
Electron transport chain
Welcome to this story about cell energy
The goal is explaining how cells make ATP
It happens in the mitochondria which you can think of
As the cell’s energy factory
Mitochondria are double-membraned organelles,
An inner membrane and an outer one as well
The mitochondrial matrix is the fluid inside
It’s where reactions like Krebs cycle reside
Glycolysis and Krebs make NADH
and FADH2 from energy in food
These electron carriers make their way
From the matrix to the inner membrane.
And that’s where you find the electron transport chain
It’s a series of enzymes embedded in the membrane,
Which take the electron carrier’s electrons
And uses their energy for pumping protons
The mitochondrial electron transport chain
Uses electron energy for pumping protons
From the mitochondrial matrix to the intermembrane space
Increasing proton concentration in that place,
The only way the protons can escape
Is through a channel and an enzyme, ATP synthase.
Which uses diffusing protons’ kinetic energy
To make ATP, from ADP and P
The chain is a series of enzymes in a row
Each accepts electrons, then lets them go
To the next carrier in this transport chain.
It’s kind of organized like a bucket brigade
What drives electrons down this enzymatic series
Is the growing level of each carrier’s electronegativity
And to oxygen electrons ultimately fall
It’s the most electronegative of them all
It’s NADH that starts this run
Donating electrons to Complex number I
This powers active transport as protons are displaced.
And get pumped from the matrix to the intermembrane space
From Complex I electrons flow to
Ubiquinone, also known as “Q”
Which floats through the inner membrane happily
And brings its electrons to Complex III
And you can guess the function of Complex III .
It’s another proton pump using electron energy
Protons jam up in that intermembrane compartment
Like a hundred people in a one bedroom apartment!
Complex II is for FADH2
Which donates electrons, which then get passed to Q
Which once again passes them to Complex III
Which pumps protons using electron energy
From Complex III the electrons proceed
To another mobile carrier, Cytochrome C
Which donates the electrons to Complex IV
Another proton pump, could you ask for more?
After Complex IV electrons flow,
To oxygen which is ever so
Electronegative it pulls electrons down the chain,
Keeping them moving like the cars of a train.
And as O2 does this electron grabbing trick,
It also grabs protons from the matrix.
They all combine to form H2O
Electron transport chain, watch it go!
Now all these protons in the intermembrane space
Are trapped they can’t get out of that place
‘Cause protons are charged and could never get through
A phospholipid bilayer, they can’t diffuse
But like all particles, they’re dying to go
From where their concentration’s high to where it’s low
Stuck in the intermembrane space they're frustrated.
To diffuse to the matrix, they’re highly motivated.
And this gradient’s been made steeper by O2
Which absorbs protons from the matrix stew,
So from proton pumping, and oxygen’s actions.
Add another force, electrochemical attraction!
Think of all those trapped protons, each one’s positive.
The matrix, in comparison is negative.
Opposites attract, so the protons are dying
To get to matrix, oh how they’re trying!
There’s only one channel that let’s the protons pass,
And they use it like high school students busting out of class,
It’s a channel and an enzyme, it’s ATP synthase
The closer in this game, an energy ace
ATP synthase is embedded in the inner membrane
How it works is so cool it’s insane.
It’s got channels for diffusing protons running right through it.
When cells make ATP, well watch how they do it
The matrix side of ATP synthase has binding sites
For ADP and P which come in and bind.
And as ATP synthase lets protons barge through
Their kinetic energy gets put to use.
Like water through a turbine proton movement generates rotation.
Changing synthase’s binding site conformation.
Which catalyzes chemical bond formation.
ADP and P make ATP that energy sensation!