Chemiosmotic hypothesis - class-X

Mitochondria are the primary sites of aerobic respiration and are famously referred to as the powerhouses of the cell because they produce the majority of ATP.

One molecule of 3-phosphoglyceric acid enters the glycolytic pathway after the initial steps. Its complete oxidation through glycolysis and the Krebs cycle yields 16 ATP molecules.

Fructose-1,6-bisphosphate is already phosphorylated. It bypasses the initial investment phase of glycolysis, resulting in a net gain of 40 ATP molecules upon complete oxidation.

Photosynthesis is an anabolic process, which helps in forming ATP, where it is called as energy currency. During the light reaction photophosphorylation takes place producing ATP and $NADPH _2$ which is used as energy source for dark reaction.

Peter Mitchell proposed a theory to explain the production of ATP which is 'Mitchell's chemiosmotic coupling hypothesis'. According to this theory:

The standard free energy change for the hydrolysis of ATP to ADP and inorganic phosphate is approximately 7.3 to 7.6 kcal/mol under physiological conditions.

Cyanide inhibits cytochrome c oxidase, blocking the electron transport chain and halting ATP production. Injecting ATP provides the necessary energy for vital cellular functions that would otherwise fail.

Peter Mitchell proposed a hypothesis known as the chemiosmotic hypothesis that an electrochemical concentration gradient of protons across a membrane could be utilized to make ATP. He linked this process to osmosis, the diffusion of water across a membrane, this is the reason it is called chemiosmosis.

A) Along with ATP, ${ NADPH } _{ 2 }$ is also produced.
B) Along with ${ NADPH } _{ 2 }$, ATP is also produced.

In the conversion of PGAL to 1,3-bisphosphoglycerate, the phosphate group is added via inorganic phosphate (Pi) and oxidation, not by transferring a phosphate from ATP.

Mitochondria and chloroplast both have:

• A double membrane surrounding the organelles.
• Purportedly prokaryotic origins according to the endosymbiotic theory which suggests that mitochondria and chloroplast were once prokaryotic bacteria engulfed by endocytosis in early eukaryotes.
• Their own circular DNA which codes for certain enzymes required for the chemical reactions that take place in these organelles.
• Their own 70S ribosomes made up of 50S and 30S subunits to translate proteins
• The enzyme ATP synthase which utilizes the energy released from the movement of protons across it (proton-motive force) to phosphorylate ADP to ATP. (Thus, another similarity would be that they both produce ATP)
• Electron transport chains, which are embedded in the inner mitochondrial membrane and thylakoid membrane in mitochondria and chloroplasts respectively.

The chemiosmotic hypothesis of ATP synthesis in chloroplasts is based on proton gradient. The chemiosmotic hypothesis was explained by P. Mitchell in 1961. He recieved noble prize for it in 1978. ATP synthesis is linked to the development of a proton gradient across the membrane of the thylakoid of chloroplast and proton accumulation is towards the inside of the membrane i.e. in the lumen. 

Cells convert light energy is converted into chemical energy. During this process, a phosphate is added to adenosine diphosphate molecule to cause the formation of ATP.

Oxidative phosphorylation is the process where ATP is formed as a result of the transfer of electrons from NADH or FADH2 to O2 by a series of electron carriers, coupled with chemiosmosis.

ATP was discovered by Karl Lohman. ATP is the energy currency of our cell. It is formed as a result of phosphorylation.

The chemiosmotic hypothesis states that the energy stored in a proton gradient across the inner mitochondrial membrane drives the synthesis of ATP by ATP synthase.

Chemiosmosis is the movement of ions across a selectively permeable membrane, down their electrochemical gradient. More specifically, it relates to the generation of ATP by the movement of hydrogen ions across a membrane during cellular respiration or photosynthesis. Peter D. Mitchell proposed the chemisomotic hypothesis in 1961. The theory suggests essentially that most ATP synthesis in respiring cells  comes from the electrochemical gradient across the inner membranes of mitochondria by using the energy of $NADH _2$ and $FADH _2$ formed from the breaking down of energy-rich molecules such as glucose.

The chemiosmotic theory, proposed by Peter Mitchell, explains that ATP synthesis in both chloroplasts and mitochondria is driven by the electrochemical gradient of protons across the membrane.

The CF0-CF1 complex is the ATP synthase enzyme found in the thylakoid membrane of chloroplasts, responsible for synthesizing ATP during the light reactions.

The Calvin cycle consists of: 1. Carboxylation (CO2 + RuBP), 2. Reduction (using ATP/NADPH to form sugar), and 3. Regeneration (reforming RuBP). The sequence is 3, 1, 2.

Carboxylation of the dark reaction (Calvin cycle) does not directly involve ATP synthesis or consumption. The enzyme RuBisCO catalyzes CO2 fixation with RuBP without ATP. Both reduction and regeneration phases consume ATP, and cyclic photophosphorylation produces ATP.

Glycolysis (EMP pathway) produces a net gain of 2 ATP molecules per glucose molecule through substrate-level phosphorylation. While 4 ATP are grossly produced, 2 ATP are consumed in the energy investment phase, resulting in a net yield of 2 ATP.

ATP captures chemical energy obtained from the breakdown of food molecules and its hydrolysis (ATP to ADP + Pi or ADP to AMP + Pi) releases energy that can be used to drive various energy-requiring processes in cells. So, the correct option is 'True'.

Photolysishappens in the thylakoids, producing H+ ions inside the thylakoid membrane., a gradient of hydrogen ions will form across the membrane, ATP synthase take the advantage of this gradient, by allowing hydrogen ions to leak out of the membrane capturing their energy and phosphorylating ADP into ATP, while another statement is correct for mitochondria.

  In the given question, the correct statements are as follows:

(i) F1 headpiece contains the site for the synthesis of ATP from ADP+Pi.

(ii) F0 part forms the channel through which protons cross the inner membrane.

(iii) For each ATP produced, 2H+ pass through F0 from the intermembrane space to the matrix down the electrochemical proton gradient.

So, the correct answer is '(i),(ii) and (iii)'.

ATP synthase is also called complex V. It is the final enzyme in the oxidative phosphorylation pathway and utilizes the energy stored in a proton gradient across a membrane to drive the synthesis of ATP from ADP and phosphate (Pi).

According to the chemiosmotic theory of Peter Mitchell, a proton gradient created by the ETS across the membrane leads to the passive movement of protons from the intermembrane space into the matrix or the stroma, through ATP synthase present on the inner membrane. The passive energy released by the protons is used for the synthesis of ATP from ADP. If a proton gradient breaksdown there will be no synthesis of ATP and no movement of protons across the membrane.

NADH and FADH$ _{2}$ transfer their electrons to molecules near the beginning of the transport chain. As electrons are passed down the chain, they move from a higher to a lower energy level, releasing energy. Some of the energy is used to pump H$^{+}$ ions, moving them out of the matrix and into the intermembrane space. The energy released in these reactions is captured as a proton gradient, which is then used to make ATP in a process called chemiosmosis. Together, the electron transport chain and chemiosmosis make up oxidative phosphorylation. 

The chemiosmotic theory explains how ATP is generated from mitochondria by electron transport chain. The chemiosmotic theory was developed by the British biochemist, Peter Mitchell, to explain the mechanism of oxidative phosphorylation in mitochondria (and photophosphorylation in chloroplasts). 

ATP is not a protein, it is a nucleotide. Proteins are made up of amino acids. While ATP is a nucleotide consisting of an adenine base attached to a ribose sugar, which is attached to three phosphate groups. 

The Hill reaction is defined as the photoreduction of an electron acceptor by the hydrogens of water, with the evolution of oxygen. In vivo, or in the organism the final electron acceptor is NADP⁺. We can measure the rate of the Hill reaction in isolated chloroplasts. first demonstrated by Robert Hill in 1939, in which illuminated chloroplasts evolve oxygen when incubated in the presence of an artificial electron acceptor (e.g. Ferricyanide). The reaction is a property of photosystem II. 

The synthesis of ATP is called phosphorylation. If it occurs in the presence of light, it is called photophosphorylation, that occurs during photosynthesis in the chloroplast. Mitochondria perform oxidative and substrate level phosphorylation.

• There is a proton gradient created across the thylakoid membrane. The breakdown of this gradient is important because it leads to the release of energy. The gradient is broken down due to the movement of protons across the membrane to the stroma through the transmembrane channel ADP ATP of the F0 of the ATPase. 
• The ATPase enzyme consists of two parts: F0 and F1. This breakdown provides enough energy to cause a conformational change in the F1 particle of the ATPase, which makes the enzyme synthesize ATP.

During glycolysis, one molecule of glucose is broken down into two molecules of pyruvate, yielding a net gain of 2 ATP. In lactic acid fermentation, the pyruvate is converted to lactic acid without further ATP production.

Using the same calculation as before: 686 kcal / 12 kcal/ATP = 57.16. The maximal number of ATP is 57.