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Chemiosmosis Hypothesis of ATP Synthesis


Before starting the article related to this topic, let’s see some questions such as how the chemiosmotic hypothesis explains ATP formation in mitochondria and chloroplast.

Practice Important MCQ 

Is there any difference between chloroplast and mitochondrial chemiosmotic mechanisms? What is a proton gradient? who discovers this hypothesis?

Video of chemiosmotic hypothesis

Chemiosmosis Hypothesis was given by Peter Mitchell in 1961.
This theory gives us accurate information about the synthesis of ATP.

Also, read Calvin’s Cycle

Also, read Photorespiration

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According to this, it explains the mechanism of how the synthesis of ATP takes place in Mitochondria and Chloroplast.
How ATP is formed during Electron Transport System (ETS) in Mitochondria and Light Reaction in Chloroplast is explained correctly in this hypothesis.
The Chemiosmotic Hypothesis explains the whole process by which ATP is produced in Photosynthesis & Respiration and respiration.
According to Chemiosmotic, ATP synthesis depends on the gradient of protons, which is formed across the membrane (Proton Gradient develops across the membrane).
This membrane is of mitochondrial membranes in respiration, the same membrane is of thylakoid membrane in photosynthesis.
However, here Photosynthesis protons act in the lumen of the thylakoid.
In the same respiration (in Respiration), protons are collected in the inner membrane space.

Formation Of Proton Gradient Thylakoid

Because in the process of photosynthesis, when the light reaction occurs, the water molecules are broken.
Water molecules break down in the lumen of the thylakoid so that hydrogen ions or protons accumulate in the lumen of the thylakoid.
When electrons move from one photosystem to another, then protons move across the Membrane of the Thylakoid.
Therefore, the number of protons increases in the lumen of the thylakoid, creating a proton gradient on either side of the membrane.
Along with this, the value of PH starts increasing in the lumen of the thylakoid.

A membrane, a proton pump, a proton gradient, and ATPase Enzyme – are required for chemosmotic

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What is the importance of the Proton Gradient?

The formation of a proton gradient is necessary because when the proton gradient is broken. So energy is released, (release of energy due to breakdown of proton gradient), this energy is used in the synthesis of ATP.
This proton gradient breaks down due to proton movement.

Chloroplasts have some special channels, which are named coupling factors. Such as CFo – CF1 (Coupling factor).
CFo – CF1 are present in the membrane of the thylakoid, they contain ATPase enzyme.
These channels are transmembranes that do the pumping of protons.
The CF1 portion of the protein channel protrudes on the outside of the thylakoid membrane, and its
The direction is towards the stroma.
CFo – CF1 channels help in the facilitated diffusion of a proton across the membrane.
When the proton gradient breaks, a large amount of energy is released, which activates the CF1 part in such a way that its ATPase enzyme also becomes active, and therefore ATP production begins.

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How is the proton gradient developed in the thylakoid?

When electrons move from one photosystem to another photosystem during the light reaction, hydrogen ions break through the stroma into the lumen of the thylakoid itself.

In this way, the number of protons starts increasing here and the formation of the proton gradient starts.


1-Who proposed the Chemiosmotic Hypothesis?
The Chemiosmotic hypothesis was proposed by Peter Mitchell in 1961.
2-Where do protons or hydrogen ions gather during the light reaction?
Protons or hydrogen ions are accumulates in the lumen of the thylakoid.
3- What are the requirements of the Chemiosmotic Hypothesis?
For this – a membrane, a proton pump, a proton gradient, and an ATPase enzyme
4-Where does the Chemiosmotic Hypothesis work?
It explains the formation of ATP in mitochondria during respiration and ATP formation in chloroplast during photosynthesis.

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In this post, we have tried to explain Chemiosmotic Hypothesis in a simple way.

Nevertheless, if you have any suggestions or updates and if you see any mistakes, then you must tell us.

We will try our best to update your suggestion or any mistake which happened somewhere in the post.

Thank you very much for giving your valuable time.

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