Metabolism and Energy Transformation in Body Cells - Renata Armenakovna Petrosova 2004

Primary Synthesis of Organic Compounds. Photosynthesis
Phases of Photosynthesis

Analyzing the General Equation of Photosynthesis raises A number of questions. How is oxygen produced? Which of the two substances—Water or carbon dioxide—is its source? How does light influence Chemical Reactions? What is its role in this process? How do the binding and reduction of carbon dioxide take place?

These questions remained unresolved for a long time. In the 1940s, using the radioisotope labeling method, researchers established that oxygen originates not from carbon dioxide, as had long been assumed, but from water.

A radioactive oxygen isotope, 180, was introduced into the water molecule. Plants were watered with this labeled water so that it would participate in photosynthesis. Analysis of the reaction products showed that all of the radioactive oxygen was present in the released oxygen:

CO2+ H218O

Class="center">ImageMETABOLISM/metabolism.files/image006.png" width="29"/>

C6H12O6 + 18O2

Further research revealed that photosynthesis occurs in two phases: the light-dependent and light-independent (dark) phases (Fig. 10).

Image

Fig. 10. General scheme of photosynthesis

The entire variety of reactions taking place here can be divided into two groups:

1) the photolysis of water driven by light energy, accompanied by The formation of hydrogen and the release of free oxygen, along with the simultaneous accumulation of energy through ATP synthesis and the binding of hydrogen to a carrier;

2) the fixation of carbon dioxide, its reduction by hydrogen, and the Synthesis of glucose utilizing ATP energy.



Last update: 13/08/2026

Editorial and Educational Adaptation: This material has been compiled based on the primary/original source text. The project team performed an editorial review, corrected technical inaccuracies, structured sections, and adapted the content for an educational format.

What was processed:

  • elimination of formatting defects (OCR errors, structural breaks, corrupted characters);
  • editorial organization of content;
  • standardization of terminology in accordance with academic sources;
  • verification of factual statements against the original source text.

All mentions of the author, publication year, and origin of the primary text have been preserved in accordance with the source.