Question 26

Water supplies electrons in the light reactions of photosynthesis.

During photosynthesis, water plays a crucial role by supplying the electrons needed in the light reactions, which are essential for generating energy-rich molecules.

A) Combine with carbon dioxide

While water does interact with carbon dioxide in the process of photosynthesis, its primary function is not to combine with it. Instead, water's critical role is in providing electrons during the light-dependent reactions, which is separate from the direct combination with carbon dioxide.

B) Absorb light energy

Water does not absorb light energy; this function is primarily carried out by chlorophyll and other pigments within the chloroplasts. Therefore, while water is essential for photosynthesis, it does not absorb light energy itself.

C) Supply electrons in the light reactions

Water is fundamental in photosynthesis as it supplies electrons during the light reactions. When water molecules are split through a process called photolysis, they release electrons that are vital for the electron transport chain, thereby contributing to the production of ATP and NADPH.

D) Transport hydrogen ions in the dark reactions

Water does not transport hydrogen ions in the dark reactions. The dark reactions, or Calvin cycle, utilize products from the light reactions, such as ATP and NADPH, rather than relying on water directly for transporting hydrogen ions.

Conclusion

The role of water as a supplier of electrons in the light reactions is essential for the overall process of photosynthesis. Other options incorrectly attribute functions to water that it does not perform, highlighting the importance of understanding the specific contributions of each component in photosynthesis. Thus, option C is the only accurate representation of water's function in this crucial biological process.