Where do the electrons that are excited in photosystem II come from?

• A. CO_2..
• B. O_2..
• C. Glucose.
• D. Photosystem I.
• E. Water.

Answer: (E)

Verified step by step guidance

1. Understand the role of photosystem II in the process of photosynthesis. Photosystem II is responsible for capturing light energy and using it to excite electrons.
2. Recognize that photosystem II is part of the light-dependent reactions of photosynthesis, which occur in the thylakoid membranes of chloroplasts.
3. Identify the source of electrons for photosystem II. The electrons are derived from the splitting of water molecules, a process known as photolysis.
4. During photolysis, water ( ${H2}_O$ ) is split into oxygen ( $O2$ ), protons ( $H+$ ), and electrons. These electrons are then transferred to photosystem II.
5. Conclude that the electrons excited in photosystem II originate from water, not from CO2, O2, glucose, or photosystem I.