Photosynthesis: Electron Transport

Study Notes

Electron transport is a critical stage in photosynthesis, generating ATP and NADPH for the Calvin cycle.

Electron transport chain: A series of protein complexes (electron carriers) in the thylakoid membrane that facilitate electron transfer.
Plastocyanin: A copper-containing protein that plays a key role in electron transport.
Cytochrome b6f complex: A protein complex that receives electrons from plastocyanin and passes them to photosystem I.
Photosystem I (PSI): Receives electrons from the cytochrome b6f complex and generates a proton gradient.

Light-dependent reactions: Light energy excites electrons in photosystem II (PSII), which are then transferred to the electron transport chain.
Electron transport: The electron transport chain passes electrons from PSII to PSI, generating a proton gradient across the thylakoid membrane.
Proton gradient: The gradient is used to produce ATP through chemiosmosis.
NADPH production: Electrons from PSI reduce NADP+ to NADPH, which is used in the Calvin cycle.

Electron transport generates ATP and NADPH for the Calvin cycle in photosynthesis.

Electron transport chain: a series of protein complexes (electron carriers) in the thylakoid membrane that facilitate electron transfer.
Plastocyanin: a copper-containing protein that plays a key role in electron transport.
Cytochrome b6f complex: a protein complex that receives electrons from plastocyanin and passes them to photosystem I.
Photosystem I (PSI): receives electrons from the cytochrome b6f complex and generates a proton gradient.

Light energy excites electrons in photosystem II (PSII), which are then transferred to the electron transport chain.
The electron transport chain passes electrons from PSII to PSI, generating a proton gradient across the thylakoid membrane.
The proton gradient is used to produce ATP through chemiosmosis.
Electrons from PSI reduce NADP+ to NADPH, which is used in the Calvin cycle.

Photosynthesis: process by which plants, algae, and some bacteria convert light energy into chemical energy
Overall Equation: 6 CO2 + 6 H2O + light energy → C6H12O6 (glucose) + 6 O2

Occur in thylakoid membranes of chloroplasts
Light energy excites electrons, which are used to generate ATP and NADPH
Two stages:
- Light absorption: light energy is absorbed by pigments (e.g., chlorophyll)
- Electron transport: electrons are passed along a series of electron carriers, generating ATP and NADPH

Occur in stroma of chloroplasts
ATP and NADPH from light-dependent reactions are used to convert CO2 into glucose
Three stages:
- Carbon fixation: CO2 is fixed into a 3-carbon molecule
- Reduction: 3-carbon molecule is reduced to form glyceraldehyde 3-phosphate (G3P)
- Regeneration: G3P is used to regenerate RuBP, the 5-carbon molecule that initiates the cycle