Question

A diagram of chloroplast stroma and thylakoid lumen showing chemical energy, ferredoxin, ferredoxin-N A D p reductase, A D P synthase, and oxygen-evolving complex.
Which corrections would change the diagram to accurately model the light-dependent reaction of photosynthesis? Check all that apply.

CO2 should be changed to H2O.
ADP and ATP need to be switched.
e– should be changed to H+.
Chemical energy should be changed to light energy.
PSII and PSI need to be switched.

Answer 1

All five corrections. Briefly why:

- CO2 → H2O: The light reactions use water (split by the oxygen‑evolving complex) as the electron source, not CO2.
- Switch ADP and ATP: ADP + Pi is the substrate and ATP is produced in the stroma by ATP synthase.
- e– → H+: ATP synthase translocates protons (H+), not electrons; electrons flow through the ETC.
- Chemical energy → Light energy: The driving input for the light reactions is light energy (which is converted into chemical energy, ATP/NADPH).
- Switch PSII and PSI: Electrons flow from PSII (where water is split) to PSI (which reduces ferredoxin/NADP+), so the photosystems must be in that order.