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Reactions of the First Stage of Photosynthesis

The first stage of photosynthesis is the process by which plants take energy from sunlight and convert it into sugar. Light energy becomes chemical energy. Cell membranes called chloroplasts contain chlorophyll, a pigment that absorbs light energy from red and blue light waves. A second stage of photosynthesis removes carbon dioxide from the atmosphere and releases oxygen in return.

Basic Reaction
- Photosynthesis is broken down into two stages. The basic reaction for both stages takes six water molecules plus six carbon dioxide molecules and produces sugar plus six oxygen molecules. The chemical formula is 6H2O plus 6CO2 yields C6H12O6 plus 6O2.
Light-dependent Reaction
- The first stage of photosynthesis is composed of the light-dependent reaction. It derives its name from the dependence upon sunlight and occurrence in the daytime. Sunlight strikes the chlorophyll in the plant; light is absorbed with the exception of green wavelengths.
Splitting Water
- This first step of photosynthesis divides water, H2O, into its component parts of hydrogen and oxygen. The oxygen releases into the atmosphere. This process is critical to the production of oxygen, an essential element for life. The hydrogen is used in the second stage of photosynthesis as a reducing agent for carbon dioxide.
Energy Conversion
- Storage of the energy created in the first stage of photosynthesis involves the creation of adenosine triphosphate, or ATP, and nicotine adenine dinucleotide phosphate, or NADP. These substances store the chemical energy and transport it. NADP acquires a hydrogen atom and becomes NADPH. They are used in the second stage of photosynthesis during the formation of sugar.

Nature