What happens in each step of photosynthesis

Photosynthesis is the biochemical reaction that makes life on earth possible for us. Let's start at the very beginning, with the word: It is derived from the three Greek words phos (light), syn (together) and thesis (to put). Photosynthesis, to put it simply, means: Plants (and certain bacteria) use light, water and carbon dioxide to put something new together: namely glucose and oxygen. So: With the help of solar energy, energy-rich organic substances are created from low-energy inorganic substances.

Chemically speaking, the following formula describes photosynthesis:
6 CO2 + 6 H.2O + light energy → C6H12O6 + 6 O2

Here it can be seen that water (H.2O) and carbon dioxide (CO2) are needed so that sugar or carbohydrates (C6H12O6) and oxygen (O2) can arise. In detail, the process of photosynthesis is very complex and consists of several interdependent processes. Important: In photosynthesis, one speaks of a redox reaction, i.e. a reduction-oxidation reaction. So there is both a reduction - i.e. a reaction with oxygen - and an oxidation - i.e. the withdrawal of oxygen.

But where exactly does photosynthesis take place? The green plants get their color from the green leaf pigment, chlorophyll (“chloro” comes from the Greek and means “green”). The chlorophyll is found in the membranes of the chloroplasts, the organelles in the cells of plants. Very important: the chlorophyll can absorb sunlight, which is required for the process. The entire photosynthesis then takes place in the chloroplasts, which are only a few micrometers in size. There are sometimes many hundreds of chloroplasts in a single cell.


For the chemistry experts:
In general, photosynthesis can be divided into two processes that are inseparable for its success: the light reaction (primary or photo reaction) - here chemical energy is provided - and the dark reaction (secondary or synthesis reaction), which uses the chemical energy from the light reaction Synthesis of energy-rich substances uses.

For us as humans it is particularly important in photosynthesis: It creates a "waste product", the oxygen that is essential for us and other living beings. At the same time, the CO2, which is toxic to us, is broken down as it is used up. A perfect balance.