This theory was proposed by Peter D. Mitchell — , a British biochemist. The discovery of ATP synthase and the pH difference across the thylakoid had the bioenergetics community consider the validity of his hypothesis.
In the s, he knew about the phenomenon of membrane potential in which the inner side of the membrane being negative relative to its environment. However, how living organisms produce ATP biologically was not well established. The mitochondria have long been known as the organelles responsible for ATP synthesis.
However, how these organelles generate ATP was not very clear. It was initially presumed to relate to substrate-level phosphorylation as what happens in glycolysis. Mitchell proposed that ATP could also be produced by chemiosmosis. He showed that ATP synthesis was coupled to an electrochemical proton gradient. This provided the basis as to how oxidative phosphorylation led to ATP synthesis. Chemiosmosis is an energy-coupling mechanism employed by living organisms to produce ATP.
In respiring cells, it is one of the major steps of cellular respiration. To further explain the process of chemiosmosis and describe how it is a part of cellular respiration, see the diagram below. The figure above is a schematic diagram of the mitochondrion. It is regarded as the powerhouse of the cell because most ATPs are produced here.
It is specialized for ATP synthesis. Take note that the organelle is a double-membraned structure. The mitochondrial membrane is made up of an outer membrane and an inner membrane. Both layers consist of lipid layers that prohibit the easy passage of ions. In between the two membranes is the intermembrane space. The inner membrane forms many infoldings called cristae. The space within the inner membrane is called the mitochondrial matrix. The matrix is the location of the citric acid cycle, a cyclic metabolic reaction where food molecules are churned to generate energy-rich phosphate compounds.
The pyruvate from glycolysis is converted into acetyl CoA that will enter the mitochondrion for complete oxidation and degradation into carbon dioxide. Once reduced, ATP synthesis occurs at lower energy levels. The search for an 'intermediate' linking electron flow and ATP synthesis led to the discovery of post-illumination ATP synthesis by thylakoids, where turnover occurs in the dark. Once interpreted by P.
It is also the method used in the light reactions of photosynthesis to harness the energy of sunlight in the process of photophosphorylation. The overall result of these reactions is the production of ATP from the energy of the electrons removed from hydrogen atoms.
These atoms were originally part of a glucose molecule. What is the citric acid cycle? See all questions in Aerobic Respiration. Impact of this question views around the world. You can reuse this answer Creative Commons License.
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