Which of the following constitutes Hill reaction

Options

A. Photolysis by chloroplasts
B. Photolysis of water by isolated chloroplasts forming ATP and NADPH
C. Photolysis of water by isolated illuminated chloroplasts causing reduction of some chemicals and liberation of oxygen
D. Photolysis of water liberating oxygen and hydrogen by illuminated isolated chloroplasts

Answer

**Step-by-Step Solution:**

1. **Understanding the Hill Reaction**: The Hill reaction was discovered by Robert Hill in 1939. It describes a light-driven process that involves the transfer of electrons from water to certain reagents, known as Hill reagents.

2. **Identifying Key Components**: The Hill reaction specifically involves isolated illuminated chloroplasts, which are the sites where photosynthesis occurs. The process involves the photolysis (light-driven splitting) of water.

3. **Chemical Changes During the Reaction**: During the Hill reaction, water (H2O) is oxidized, resulting in the liberation of oxygen (O2). At the same time, a Hill reagent (like ferricyanide) is reduced to a different form (like ferrocyanide).

4. **Analyzing the Options**: The options provided in the question include:
- Photolysis by chloroplast
- Photolysis of water by isolated chloroplast forming ADP and NADPH
- Photolysis of water by isolated illuminated chloroplast causing the reduction of some chemicals and the liberation of oxygen
- Photolysis of water liberating oxygen and hydrogen by illuminated isolated chloroplast

5. **Selecting the Correct Answer**: The correct description of the Hill reaction is: "Photolysis of water by isolated illuminated chloroplast causing the reduction of some chemicals and the liberation of oxygen." This option accurately reflects the process of the Hill reaction.

**Final Answer**: The Hill reaction is constituted by the photolysis of water by isolated illuminated chloroplast causing the reduction of some chemicals and the liberation of oxygen.

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