Is Light Needed for Photosynthesis?

Photosynthesis is one of the most vital occurrences in nature as all living organisms require and benefit from its byproduct: the air produced and the food that is harvested. A strong grasp and understanding of this awe-inspiring cycle is arguably more important for humanity now than it ever has been as the problem of deforestation and other such threats to the abundance of forests is greatly contributing to the build up of carbon dioxide in the atmosphere.

Significance

Photosynthesis serves as a vital component for the natural world. It is a process performed mostly by plants and the occasional bacteria and protistans that provide the oxygen in order to sustain life. Photosynthesis is the natural mechanism in plants that converts idle light energy into usable chemical energy and produces oxygen as well as storable energy in the form of a simple sugar. Essentially, plants create air for us to breathe, food for us to eat and sustenance for themselves as well all in one process.
There are two stages to photosynthesis: the first requiring either natural or artificial light and the second simply requiring the initial energy stored from the first stage, which could easily be done in the dark.
The chemical process is expressed as the following: 6CO2 + 6H2O (+ light energy) ----> C6H12O6 + 6O2, or six molecules of water plus six molecules of carbon dioxide produce one molecule of sugar plus six molecules of oxygen.

The First Stage of Photosynthesis

Known as the light reaction, or light dependent process, this first stage involves the utilization of carbon dioxide from the air and water from the soil. This is where light is absolutely needed as it enters the leaf of the plant via chlorophyll, located and organized in clusters in the thylakoid membrane, which is a pigment that absorbs all hues of light except for green, which is reflected back to our eyes and is the reason that leaves are generally green. This activates the electrons to a higher energy state and, through an electron transport process, the energy harvested is stored as ATP (adenosine triphosphate) and NADPH (nicotine adenine dinucleotide phosphate). Simultaneously in this process, water is split into its basic components and releases oxygen as a byproduct.

The Second Stage of Photosynthesis

The dark reaction, also called the light indepedent process and the Calvin cycle, takes place in the stroma within the chloroplast. This process does not require light as it uses the carbon dioxide from the air and the stored ATP and NADPH from the previous cycle in order to convert them into sugar. The sugar is transported through veins in the leaf to the fruits, stems and roots of the plant. Some of this sugar is used immediately for energy and some is stored as starch. Plants usually make more food and energy than they need, allowing us to eat the plant directly or its products such as fruits and vegetables.

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References

• Estrella Mountain Community College; Photosynthesis
• Biology at Clermont College; Photosynthesis