In the context of organic chemistry reactions, which molecule acts as an electron carrier connecting two photosystems in the light reactions of photosynthesis?

• A. Plastoquinone
• B. ${\mathrm{FADH}}_2$
• C. ${\mathrm{NADPH}}_{}$
• D. $\mathrm{ATP}$

Answer: (A)

Verified step by step guidance

1. Understand the role of electron carriers in photosynthesis: In the light reactions of photosynthesis, electron carriers are molecules that transport electrons from one molecule to another, facilitating the conversion of light energy into chemical energy.
2. Identify the two photosystems involved: Photosynthesis involves two main photosystems, Photosystem I (PSI) and Photosystem II (PSII), which work together to capture light energy and generate ATP and NADPH.
3. Recognize the function of Plastoquinone: Plastoquinone is a lipid-soluble molecule that acts as an electron carrier between Photosystem II and the cytochrome b6f complex, which is part of the electron transport chain in the thylakoid membrane.
4. Differentiate between the given options: FADH2 and NADPH are electron carriers, but they are not involved in connecting the two photosystems in the light reactions. ATP is an energy carrier, not an electron carrier.
5. Conclude with the correct electron carrier: Based on the role of Plastoquinone in the electron transport chain, it is the molecule that connects the two photosystems by transferring electrons from Photosystem II to the cytochrome b6f complex, facilitating the continuation of the light reactions.