This is the second in a series of three music videos about the light reactions of photosynthesis.

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Electron flow in chloroplasts happens along pathways
In which photosystems harvest light and send electrons on their way
A photosystem is a protein complex in the thylakoid membrane,
That sends electrons to an electron transport chain

The non-cyclic pathway is one way electrons flow,
As photosystems harvest light away electrons go!
Electrons stream from Photosystem 2 to Photosystem 1
A current that’s powered by the sun.

Photosystem II’s antenna complex starts the photon capture
Electrons bounce in response with energetic rapture
And all around the world, from Berkeley down to Haiti
Electrons find reaction center P680.

There these electrons, bounce like a ball,
But unlike all the times before they rise but do not fall
A primary electron acceptor grabs them away,
Leaving the reaction center in an oxidized state

That electron acceptor in the thylakoid membrane
Sends the ‘lectron over to the ‘lectron transport chain.
A series of proteins that takes these electrons
And uses their energy for pumping protons

From the stroma to the thylakoid space
Packs positive protons, into that tiny place
Like charges repel, diffusion gradient’s created,
If a proton could diffuse out, it would be elated.

But the lipid bilayer prevents proton oozing,
No way there’s gonna be any simple diffusing,
There’s only one port through which protons can travel
It’s the ATP synthase channel.

The “ase” tells you this is an enzyme,
Which makes ATP all the time,
It has binding sites for ADP and P
And channels for diffusing protons whose kinetic energy

Changes the binding site’s conformation
Binding ADP with P, which for your information
Is how thylakoids make ATP
Life’s key form of energy.

From respiration this might feel familiar
ATP is made this way in mitochondria
Chemiosmosis is the name,
ATP production is the game.