Photolysis

Photolysis is a chemical reaction in which a compound is broken down by photons. It is part of the light-dependent reactions of photosynthesis.

Overview

Photolysis is a process by which molecules are broken down into smaller units through the absorption of light. The term is derived from the Greek words photo meaning light and lysis meaning to loosen or untie. Photolysis can occur in the atmosphere or in the cells of organisms.

Process

In photolysis, a molecule absorbs a photon and goes into an excited state. The energy absorbed can cause the molecule to break its chemical bonds, leading to a reaction. The products of photolysis can be different depending on the molecule and the wavelength of light. For example, in the ozone layer, photolysis of ozone molecules by ultraviolet light produces oxygen.

Role in Photosynthesis

Photolysis plays a crucial role in the light-dependent reactions of photosynthesis. In plants, chlorophyll absorbs light energy, which is then used to split water molecules in a process known as photolysis of water. This process produces oxygen, which is released into the atmosphere, and hydrogen ions, which are used in the production of ATP and NADPH.

Environmental Impact

Photolysis also has significant environmental implications. It is involved in the formation and breakdown of many atmospheric compounds that have effects on climate and air quality. For example, photolysis is responsible for the formation of the ozone layer, which protects the Earth from harmful ultraviolet radiation. However, certain pollutants can undergo photolysis to produce harmful substances. For instance, photolysis of nitrogen dioxide in the atmosphere can lead to the formation of ozone at ground level, contributing to smog.

See Also

• Photosynthesis
• Chemical reaction
• Ozone layer
• Smog