Noncyclic electron pathway (in the thylakoids)

What does a photosystem consist of?

It consists of a pigment complex and electron acceptor molecules within the thylakoid membrane

How can the pigment complex be described as?

As an antenna for gathering solar energy

How many photosystems does the non-cyclic electron pathway use?

2 (PS I and PS II)

where is the one and only place oxygen is created?

Photosystem II

What does PSII capture light in the form of?

Photons (one photon excites one electron)

What do the electrons do after they’ve been excited by the photon?

Each electron excites a chlorophyll molecule surround the PSII creating resonance energy to neighbouring chlorophyll molecules

What happens when the energy reaches the reaction center of PSII.

Once it reaches the reaction center of PSII (chlorophyll a mlc) it releases one electron

How many photons must hit PSII?

2 Photons because magnesium wants to lose 2 electrons

What is Plastoquinone Qb?

A mobile carrier (1 of 3) that picks up 2 electrons

Because P Qb picks up electrons, what else can it pick up?

2 protons (from the stroma)

How are the electrons from PS II replaced (have to be replaced)?

By the splitting of 2 H2O

What is the equation for the previous question?

2H2O → 4H+ (+) 4e- (+) O2 (diatomic)

What does the splitting of H2O also do?

Release H+ into the lumen (creating hydrogen ion concentration gradient), which was pumped into the lumen by P Qb

What is the proton gradient from?

Hydrogens

What molecule is at the end of the ETC but at the start of the noncyclic electron pathway?

O2

Where does P Qb transfer the electrons?

To the next protein complex Cytochrome b6f (proton pump protein complex)

What does cytochrome b6f do?

pumps its own 2 H+ into the lumen

What happens to the 2 electrons from cytochrome b6f?

They are released and the next carrier, plastocyanin, picks them up (carrier 2 of 3)

Where does Plastocyanin take the 2 electrons?

To Photosystem I where once again photons will excite the chlorophyll molecules, causing the reaction center to release 2 electrons (from 2 photons)

What happens to the old electrons?

They replace the 2 new electrons that were released from PS I

Where do the two new electrons go?

Once they’ve been released they go to the last carrier ferredoxin (Carrier 3 of 3)

What are the electrons transferred to?

The protein complex Ferredoxin NADP reductase

What does FNR do?

Causes 2 electrons and only one hydrogen ion (proton) to combine with NADP to form NADPH

What happens last?

ATP synthase use the ETC to generate ATP using ADP and phosphate (via PMF/Chemiosmosis)