Give an example of photochemical reaction

General
1

give an example of photochemical reaction

2

Give an example of photochemical reaction

Answer: A classic example of a photochemical reaction is photosynthesis. Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy, usually from the sun, into chemical energy stored in glucose. The general equation for photosynthesis is:

6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6O_2

In this reaction, carbon dioxide (CO_2) and water (H_2O) are converted into glucose (C_6H_{12}O_6) and oxygen (O_2) with the help of light energy absorbed by chlorophyll, the green pigment in plants.

Steps of Photosynthesis:

  1. Light Absorption:

    • Chlorophyll absorbs light energy, primarily in the blue and red wavelengths, and becomes excited.

  2. Water Splitting (Photolysis):

    • The absorbed light energy is used to split water molecules into oxygen, protons, and electrons:
      [ 2H_2O \rightarrow 4H^+ + 4e^- + O_2 ]

  3. Formation of ATP and NADPH:

    • The excited electrons move through the electron transport chain, leading to the formation of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate), which are energy carriers.

  4. Carbon Fixation (Calvin Cycle):

    • ATP and NADPH are used in the Calvin cycle to convert carbon dioxide into glucose through a series of enzyme-mediated steps.

Significance of Photosynthesis:

  • Oxygen Production: Photosynthesis is the primary source of oxygen in the Earth’s atmosphere, which is essential for the survival of aerobic organisms.
  • Energy Source: It forms the basis of the food chain by providing energy-rich glucose molecules that are consumed by heterotrophic organisms.
  • Carbon Dioxide Reduction: Photosynthesis helps in reducing the levels of carbon dioxide in the atmosphere, thereby playing a crucial role in mitigating climate change.

In summary, photosynthesis is a photochemical reaction that harnesses light energy to drive the synthesis of glucose from carbon dioxide and water, releasing oxygen as a by-product. This process is fundamental to life on Earth, sustaining both plant and animal life.