Define photosystem II reaction center P680 and photosystem I reaction center P700.

• A. P680 and P700 are chlorophyll b reaction centers that absorb at 680 and 700 nm.
• B. P680 and P700 are chlorophyll a reaction centers that absorb light at 680 nm and 700 nm, respectively, driving electron transport.
• C. They are proteins that do not participate in light absorption.
• D. They are pigments that absorb UV light only.

Answer: (B)