Arrange the following physiological events occurring during the light-dependent stage of photosynthesis in their correct chronological sequence from start to finish.
- 1Absorption of light photons by chlorophyll leading to the photo-excitation of electrons.
- 2Photolytic cleavage of water molecules into hydrogen ions (), electrons, and oxygen ().
- 3Transfer of high-energy electrons through an electron transport chain to synthesize ATP.
- 4Reduction of to by accepting electrons and hydrogen ions.
Answer
The correct sequence begins with the absorption of light photons by chlorophyll leading to photo-excitation of electrons, followed by the photolytic cleavage of water molecules into hydrogen ions, electrons, and oxygen, then the transfer of high-energy electrons through an electron transport chain to synthesize ATP, and culminates in the reduction of to by accepting electrons and hydrogen ions.
The light-dependent phase begins when light photons strike chlorophyll molecules, exciting electrons. To fill the electron hole left in chlorophyll, water undergoes photolysis to yield protons, electrons, and oxygen. As the energized electrons pass along carrier proteins in the thylakoid membrane, ADP is phosphorylated into ATP. Finally, the electrons and protons are accepted by NADP+ to form NADPH, completing the sequence.
Step-by-Step Solution
Key Concept
Sequence of events in light-dependent reactions of photosynthesis