The article is written by Pavlo Chaika, the chief editor of the "Piznavayka" magazine. Since its founding in 2013, Pavlo Chaika has been dedicated to popularizing science in the world. The main goal, both of the magazine and of this article, is to explain complex scientific topics in a simple and accessible language.



  • Simple Definition

  • Discovery

  • Importance

  • Equation

  • Examples in Plants

  • How Does It Work?

  • Stages

  • Light Reaction

  • Dark Reaction

  • References and Further Reading

    Simple Definition

    What is photosynthesis? The process of photosynthesis is one of the most important biological processes occurring in Nature. Organic substances are formed from carbon dioxide and water under the action of light; this phenomenon is called photosynthesis. The release of oxygen (vital for the existence of life on our amazing planet) is the most important product of photosynthesis.


    How did scientists discover photosynthesis? The important experiment was made by the English scientist Joseph Priestley back in 1771. He placed the mouse under the cap and five days later it died. Then he again placed another mouse under the cap, but this time there was a sprig of mint under the cap together with the mouse, and the mouse survived. “There is a process opposite to breathing” – thought the scientist after this experiment. Another important conclusion of this experiment was the discovery of oxygen, as vital to all living creatures (the first mouse died from its absence, the second survived, thanks to a sprig of mint, which produce oxygen in the process of photosynthesis).

    Then, back in 1782, the Swiss scientist Jean Senebier proved that carbon dioxide decomposes in the green organelles of plants under the influence of light. Then, after another 5 years, the French scientist Jacques Busengo discovered that the absorption of water by plants occurs during the synthesis of organic substances.

    And the final step in a series of scientific discoveries related to the phenomenon of photosynthesis was the discovery of the German botanist Julius Sachs. He proved that the volume of carbon dioxide consumed and oxygen released occurs in a 1:1 ratio.


    The leaves of any plant can be compared with a small laboratory. Organic substances and oxygen are produced in this laboratory thanks to photosynthesis. So life on Earth would not exist without oxygen and photosynthesis.

    Yet if photosynthesis is so important for life and oxygen production, then how do people live in the desert (where there is a minimum of green plants)? The fact is that land plants release only 20% of the oxygen into the atmosphere, while the remaining 80% is released by sea and ocean algae. That is why the ocean is called “the lungs of our planet”.


    What is the formula for photosynthesis? The general equation or formula for photosynthesis can be written as follows:

    Water + Carbon Dioxide + Light > Carbohydrates + Oxygen

    The chemical equation for photosynthesis can be written as follows

    6СО2 + 6Н2О = С6Н12О6 + 6О2

    Examples in Plants

    In fact, the release of oxygen is not the only reason for photosynthesis. This biological process is vital not only for people and animals but also for the plants themselves because organic substances that are formed during photosynthesis form the basis of plant activity.

    How Does It Work?

    Chlorophyll is the main engine of photosynthesis. Chlorophyll is a special pigment contained in plant cells. Among other things chlorophyll is responsible for the green color of the leaves of trees and other plants. Chlorophyll is a complex organic compound, which has an important property – the ability to absorb sunlight. By absorbing sunlight, chlorophyll activates biochemical laboratory in each small leaves, in each grass, and in each alga. Then the chemical reaction of photosynthesis takes place. The transformation of water and carbon dioxide into carbohydrates (necessary for plants) and oxygen (necessary for all living things) takes place during the reaction of photosynthesis. The mechanism of photosynthesis is a brilliant creature of Nature.


    Picture of photosynthesis.


    The process of photosynthesis consists of two stages (or cycles): light and dark. We will write in detail about each of them.

    Light Reaction

    This stage is carried out on the membranes of grana. Grana are the stacked membrane structure within chloroplasts; the direct energy of light helps the plant to make molecules that carry energy for utilization in the dark phase of photosynthesis.

    The order of the processes of the light reaction of photosynthesis is as follows:

    • Light enters the chlorophyll molecule and absorbed by the green pigment. The electron that enters this molecule goes to a higher level and takes part in the synthesis process.
    • There is a splitting of water, during which the protons are converted to hydrogen atoms under the action of electrons. Electrons spent on the synthesis of carbohydrates.
    • ATP synthesis (Adenosine triphosphate) occurs at the last stage of the light reaction of photosynthesis. ATP is an organic substance that plays the role of a kind of energy storage in biological processes.

    Dark Reaction

    The dark reaction of photosynthesis proceeds in the stroma of the chloroplast. The release of oxygen (as well as glucose synthesis) takes place during the dark reaction of photosynthesis. You may think that the dark reaction of photosynthesis occurs only at night. In fact, this is not the case – glucose synthesis occurs during all day. The light energy is no longer consumed and is not needed at this stage.

    References and Further Reading

    • Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project.
    • Jump up to: a b Bryant DA, Frigaard NU (Nov 2006). “Prokaryotic photosynthesis and phototrophy illuminated”. Trends in Microbiology. 14 (11): 488–496. doi:10.1016/j.tim.2006.09.001. PMID 16997562.
    • Reece J, Urry L, Cain M, Wasserman S, Minorsky P, Jackson R (2011). Biology (International ed.). Upper Saddle River, NJ: Pearson Education. pp. 235, 244. ISBN 978-0-321-73975-9. This initial incorporation of carbon into organic compounds is known as carbon fixation.
    • Olson JM (May 2006). “Photosynthesis in the Archean era”. Photosynthesis Research. 88 (2): 109–117. doi:10.1007/s11120-006-9040-5. PMID 16453059.
    • Steger U, Achterberg W, Blok K, Bode H, Frenz W, Gather C, Hanekamp G, Imboden D, Jahnke M, Kost M, Kurz R, Nutzinger HG, Ziesemer T (2005).

    Author: Pavlo Chaika, Editor-in-Chief of the journal Poznavayka

    When writing this article, I tried to make it as interesting and useful as possible. I would be grateful for any feedback and constructive criticism in the form of comments to the article. You can also write your wish/question/suggestion to my mail or to Facebook.