Chemiosmotic Hypothesis, History and Its Process

In this article, we will discuss a unique mechanism called the Chemiosmotic Hypothesis in which the ATP molecules are produced with the help of the ATP synthase in photosynthesis.

Aerobic and Anaerobic Respiration

History of Chemiosmotic Hypothesis

• Living things may create ATP, or adenosine triphosphate, using energy that is supplied by food, light, or a variety of other sources.
• ATP generation is connected to respiratory and photosynthetic activities, which are mediated by sophisticated redox enzymes housed in lipid membranes. This is common information today.
• Peter Mitchell's chemiosmotic hypothesis, which he initially proposed as a mechanism for this in 1961, was quickly disputed.
• On March 9, 2016, Professor Peter Rich of University College London gave a captivating talk at New York University London that traced the development of Mitchell's chemiosmotic theory and showed how a disproved hypothesis eventually became a recognised theory.
• The way Professor Rich approached Mitchell's thesis was fascinating. He discussed the several scientists whose research had inspired Mitchell's theories.
• These researchers included David Keilin with his theory of the cytochrome respiratory chain, Han Krebs with his work on the citric acid cycle, and Robin Hill with his discovery of the well-known Hill reaction and advancements in the study of photosynthesis.

Centriole

• All of this earlier research established the fundamentals of how cells produce energy and raised the question of how the power from the electron transport chain was transferred to the enzyme-producing ATP.
• Except for Mitchell, who proposed the chemiosmotic hypothesis by incorporating the broad physical and chemical concepts established by earlier scientists, no one else seemed to have a sufficient response.
• According to Mitchell's theory, the membrane in which the electron transport chain and ATP synthesis are contained is impermeable to protons, the compounds involved in the two processes are in contact with one another or the membrane's opposite, protons are exchanged across the membrane, and ultimately the two processes are separated.
• Since his concept went against conventional biology and biochemistry and occasionally outraged scientific community members, Mitchell founded a separate research facility at Glynn House in Cornwall, where he and his longtime partner, Dr Jennifer Moyle, worked to investigate their hypothesis.
• He eventually received the Nobel Prize in Chemistry in 1978, even though it took years for his idea to become accepted.

Cell Wall and Cell Membrane

Introduction

Cell Division

Process of Chemiosmotic Hypothesis

• The chemiosmosis process needs the proton gradient, ATP synthase, and proton pump, among other crucial components. The enzyme required to generate ATP molecules is known as ATP synthase. The ATP synthase enzyme comprises two subunits F0 and F1 . The F0 subunit is required to translocate protons across the membrane.
• As a result, the structure of the F1 subunit is changed, activating enzymes.
• The enzyme phosphorylates ADP, converting it into ATP by adding a phosphate group. A proton gradient that crosses the membrane serves as the primary source of propulsion for ATP synthase.

• During the light reaction phase of photosynthesis, chlorophyll absorbs light with the help of photosystems. The outcome is splitting the water molecules, which release protons and electrons through Hydrolysis.
• The released electrons are transported via the electron transport system as they energise and move up an energy level.
• Meanwhile, the membrane's internal protons assemble after being freed from the stroma. As a result, a proton gradient, a byproduct of the electron transport chain, is created.
• Photosystem I use the electrons from the photolysis of water to convert the few residual protons from NADP+ to NADPH. Eventually, the proton gradient falls, releasing energy and protons that ATP synthase F0 then transports back to the stroma.
• The F1 conformation is changed by the resultant energy, which causes the ATP synthase to convert ADP into ATP.

Cellular Respiration

• Water is photolysed in the direction of the thylakoid membrane.
• As electrons pass through the Electron transport system, H + is transferred from the stroma to the lumen.
• On the stroma side of the membrane, NADP-reductase reaction takes place.

Cell Organization