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Understanding Photosynthesis The Simplest Way

Understanding photosynthesis
Understanding Photosynthesis

If you really want to understand photosynthesis in the simplest way, then this article is for you. Today, we are going to cover photosynthesis definition, photosynthesis equation, photosynthesis diagram and even more.
so what is actually photosynthesis?
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Photosynthesis is the process whereby green plants containing chlorophyll in chloroplast will absorb solar energy from the sun in the presence of carbon dioxide and water in order to manufacture their food called carbohydrate with oxygen being given off as a by-product.

The general equation is represented as follows

6Co2+12H20+sunlight—–>C6H12O6+6O2+6H2O, In order words, 6 molecules of carbon dioxide, 12 molecules of water plus sunlight is required for this process. Also, keep in mind that 6 molecules of water are being produced. Note; The oxygen which is being described as a waste product is being used by other organisms including plants itself for cellular respiration.

However, there exist two types of photosynthesis: Oxygenic and anoxygenic photosynthesis.

Oxygenic is carried out mostly by green plants and other forms of bacterias. Anoxygenic on the other is carried out by a kind of bacteria which lacks the nucleus.

Differences between Oxygenic and Anoxygenic photosynthesis.

In oxygenic photosynthesis, light is responsible for the transfer of an electron from water to carbon dioxide to produce carbohydrate and oxygen. In order words, water(H2O) acts as an oxidizing agent by losing its electron and carbon dioxide acts as a reducing agent by accepting the loss of an electron from the water molecule. Hence water acts as the electron donor and oxygen is produced.

In anoxygenic photosynthesis, water is not the electron donor and therefore oxygen is not being produced.

This can be represented by the below equation

Oxygenic Photosynthesis  6Co2+12H20+sunlight—–>C6H12O6+6O2+6H2O

Anoxygenic photosynthesis  Co2+H2B+sunlight—–>(CH2O)+2B+H2O, where B is a variable.

Since green plants and other bacteria like cyanobacteria are able to synthesize food for themselves using sunlight, there are therefore called Autotrophs(plants, algae, and some bacteria). Heterotrophs on the other hand(humans, cows, grasshoppers, birds, fungi, amoebas) rely on autotrophs for their food.

Photosynthesis actually takes place at the level of the chloroplast.The chloroplast is made up of an outer and inner membrane, separated by a space called an intermembrane space.

The stroma is found in the interior part of the inner membrane where the dark stage of the photosynthetic reaction takes place. The stroma is filled with an aqueous fluid. In the inner membrane of the chloroplast are also stacks of flattened shaped structures called the thylakoid where the light stage of the reaction takes place. The thylakoid is being embedded with proteins and pigment molecules responsible for the absorption of light.

Photosynthesis occurs in two stages reaction: The light stage of reaction and the dark stage of reaction(the Calvin cycle). The light stage of the reaction takes place at the level of the thylakoid and the dark stage of reaction takes place in the stroma(The aqueous fluid that surrounds the stacks of thylakoids). In the light stage of the reaction, water is being oxidized to release oxygen and its electron. The high energy electron will then be transferred to ATP AND NADPH. In the dark stage of the reaction, the energy from ATP and NADPH is used for co2 fixation.

When a photon of light hits the reaction center, chlorophyll electrons become excited. chlorophyll will then release an electron require for the formation of ATP and NADPH. However, the electron produced by chlorophyll is being prevented from escaping through the electron-hole by water. This is simply by the fact that the electron-hole will be filled up by the electrons from water molecules.

ATP can also be produced by ATP synthase, which is an enzyme that enables the synthesis of ATP from ADP.


Photosystem constitutes of different types of protein which surrounds the pigment molecules responsible for the absorption of light. In photosystem 2, the photon of light will hit the chlorophyll pigment(chlorophyll a), causing its electron to be excited which is then released. In photosystem 1, the excited electrons that were released by chlorophyll will be used in the synthesis of ATP and NADPH.

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