Oxidative phosphorylation - class-XI

Riboflavin (Vitamin B2) is a precursor for the coenzymes FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide).

Respiration is a process in which respiratory substrates are broken down through oxidation accompanying with the release of energy and its storage or conservation in the form of ATP with the release of carbon dioxide as a consequence. The actual mechanism of respiration is a stepwise process in which each step is catalyzed by a specific enzyme and the energy stored in the substrate is released in a stepwise series of reactions. The energy released in the process is used up in various energy-requiring processes of organisms. 

The respiratory breakdown of glucose in the presence of oxygen is an oxidative process. During this process, several intermediates such as pyruvic acid, isocitric acid, succinic acid and oxalic acid are oxidized. Each oxidation step involves the release of 2 H which goes to reduce various coenzymes i.e. NAD+ and FAD. Reduced NAD+ and FAD released in the glycolysis and Krebs cycle finally reduce oxygen to water. This transfer of H+ and e- from NADH + H+ or FADH2 to oxygen is not a simple process and the direct transfer of electrons from coenzymes to oxygen is thermodynamically not possible. To facilitate this transfer, many intermediate cytochromes and other carriers are arranged in a series which transport electrons from NADH or FADH2 to oxygen. This sequence of electron carriers constitutes electron transport system. The electron transport proceeds from carriers that have low redox potential to those having high redox potential. The electron transport down to the energy gradient through electron transport system leads to the formation of ATP from ADP and inorganic phosphate. This generation of ATP is called oxidative phosphorylation. 

A large amount of NADH produced during glycolysis and Krebs cycle undergoes oxidation with phosphorylation of ADP to form ATP which is supported by mitochondrial electron transport assembly and ATP synthase which are integral protein complexes of the inner mitochondrial membrane. The electron transport assembly is comprised of a series of protein complexes that catalyze sequential oxidation-reduction reactions.

In  the cytoplasm, one glucose molecule breaks down into two pyruvate molecules, and creates two NADH molecules by glycolysis. Transformation of one pyruvate from cytosol to one acetyl CoA produces one NADH molecule in the mitochondrial matrix. During  each turn of Krebs cycle, each acetyl CoA is systematically processed through the cycle and produces three NADH molecules.

• Oxidative phosphorylation is the metabolic pathway in which cells use enzymes to oxidize nutrients, thereby releasing energy which is used to produce ATP. In most eukaryotes, this takes place inside mitochondria. This was explained by Leininger

In Kreb's cycle the oxidation or dehydrogenation reaction occurs 4 times as follows:

Oxidative phosphorylation-

Option 'A' is correct.

$C _4$ cycle or the Hatch-Slack pathway is a photosynthetic process in some plants. It is the first step in extracting carbon from carbon dioxide to be able to use it in sugar and other biomolecules. $C _4$ plants do not undergo phosphorylation due to their special mechanism to increase the $CO _2$ level for enzyme binding.

Co-enzymes are organic compounds, are bound to the the enzyme to make the enzyme catalytically active, but their association with the enzyme is only transient, usually occurring during the course of catalysis. Co-enzymes serve as co-factors in a number of different enzyme catalyzed reactions. The essential chemical components of many coenzymes are vitamins, e.g., coenzyme nicotinamide adenine dinucleotide (NAD) and NADP contain the vitamin niacin; flavin adenine dinucleotide (FAD) is derived from riboflavin vitamin.

Oxidative phosphorylation is an ATP generating process, which takes place in the inner membrane of mitochondria of aerobic organisms. In a generic sense, this process generates ATP via transferring electrons from $FADH _2$ or NADH via a series of complex carriers. Oxygen is a vital constituent of this process for its role as the final electron acceptor. Therefore, oxidative phosphorylation cannot take place in absence of oxygen. Hence, the correct answer is (D).

The metabolic process of releasing energy from food can be termed as oxidative phosphorylation. It occurs in the mitochondria of eukaryotic cell. In this process, the electrons are transported through different carriers ultimately to the oxygen molecule. these electrons reduce oxygen to form water and release energy which converts ADP to ATP. 

NAD$^+$ accepts electrons/H$^+$ released by water.

• Oxidative phosphorylation refers to the process by which ATP molecules (energy currency) are produced in the mitochondria.
  
• ATP is produced by the transfer of electrons from NADH or FADH2 to oxygen molecule with the help of electron carriers.
  
• Oxysomes or F0-F1 particles refers to small round structures present within the folds of the cristae of the inner mitochondrial membrane.
  
• F0 and F1 particles are found in the inner mitochondrial region and are attached to the cristae and help in ATP production and oxidation.
  

The respiratory breakdown of glucose in the presence of oxygen is an oxidative process. During this process, several intermediates such as pyruvic acid, isocitric acid, succinic acid and oxalic acid are oxidized. Each oxidation step involves the release of 2 H which goes to reduce various coenzymes i.e. NAD+ and FAD. Reduced NAD+ and FAD released in the glycolysis and Krebs cycle finally reduce oxygen to water. This transfer of H+ and e- from NADH + H+ or FADH2 to oxygen is not a simple process and the direct transfer of electrons from coenzymes to oxygen is thermodynamically not possible. To facilitate this transfer, many intermediate cytochromes and other carriers are arranged in a series which transport electrons from NADH or FADH2 to oxygen. This sequence of electron carriers constitutes electron transport system. The electron transport proceeds from carriers that have low redox potential to those having high redox potential. The electron transport down to the energy gradient through electron transport system leads to the formation of ATP from ADP and inorganic phosphate. This generation of ATP is called oxidative phosphorylation. 

Kreb cycle is also known as the citric acid cycle or tricarboxylic acid cycle takes place in the inner membrane of mitochondria. It occurs there because the necessary enzyme for the Krebs cycle, succinic dehydrogenase is only found in the inner membrane of the mitochondria.

• Glycolysis and Krebs cycle yield certain reduced coenzymes like NADH+H+ and FADH2.
• ETS is metabolic pathway of electron transport that oxidizes these coenzymes to release energy from them.

• NADH+H+ gets oxidized at Complex I of ETS and as the electrons are transferred to other Complexes, it creates a proton gradient for ATP production. One NADH+H+ yields 3 ATPs and one FADH2 yields 2 ATPs.
  
• So the correct answer is '3 ATPs'.

The electron transport system is located in the inner membrane of the mitochondria.

The process of formation of ATP during oxidation of reduced coenzymes in the electron transport chain is known as oxidative phosphorylation. This process takes place in the mitochondrial membrane because in mitochondrial membrane there are specialized particles which are known as oxysomes which contain coenzymes for electron transfer.

Formation of ATP from ADP in the presence of oxygen during the Krebs cycle is known as oxidative phosphorylation.

In the electron transport chain, one FADH2 molecule yields 2 ATP molecules upon oxidation.

Each NADH produces 3 ATP and each FADH2 produces 2 ATP. For 2 NADH and 3 FADH2: (2 * 3) + (3 * 2) = 6 + 6 = 12 ATP.

Reduced molecules like NADH+H+ and FADH2 yield energy in the form of ATP when they undergo ETC in mitochondria. NADH+H+ enter ETC at higher complex than FADH2 so they release energy as 3 ATP and 2 ATP respectively.

The Krebs cycle is the condensation of acetyl group with oxaloacetic acid and water to yield citric acid and leads to the formation of Oxalo acetic acid.

Phosphorylation is the addition of a phosphate (PO$ _{4}^{3-}$) group to a protein or other organic molecule. Phosphorylation results in the formation of ATP, which is the energy currency of cell. Phosphorylation occurs as a part of glycolysis, Kreb's cycle and HMP pathway.

Oxidative phosphorylation is a metabolic process, which is a part of respiration, which occurs in mitochondria. As a result of this process energy is released in the form of ATP.

Oxidative phosphorylation refers to synthesis of ATP by ADP and Pi driven by energy released from oxidation of reducing powers NADH and FADH2 by transfer of their electrons through electron trasnport chain to oxygen. Electron trasnport chain is present in inner mitochondrial membrane and passes the electrons down a series of carriers and pump protons into the intermembrane space. Oxygen serves as final electron acceptor in oxidation of NADH and FADH2 and the resulting proton gradient serves as energy source for the enzyme ATP synthase to synthesize ATP. So final products of oxidative phosphorylation are ATP, NAD and FAD. DPN (diphosphopyridine nucleotide), also called as NAD. Correct answers are D and B. NADP is coenzyme of photosynthetic light reactions. Puruvic acid is product of glycolysis. 

Oxidative phosphorylation is the metabolic pathway in which the mitochondria in cells use their structure, enzymes and energy released by the oxidation of nutrients to reform ATP in respiration.

Biological phosphorylation is of two types- protein phosphorylation and oxidative phosphorylation. In protein phosphorylation, the proteins get attached with a phosphate group. Oxidative phosphorylation is the metabolic pathway in which the mitochondria in cells use their structure, enzymes, and energy released by the oxidation of nutrients to reform ATP.

During one of the steps of Krebs cycle, succinic acid is converted to fumaric acid. The reaction is accompanied by coenzyme FAD (flavin adenine nucleotide). This oxidation reaction liberates less free energy as compared to other oxidation reactions. FAD$^+$ is the hydrogen acceptor in this reaction as there is very less free-energy change. In this reaction, succinic acid is oxidized to fumaric acid. At the same time, FAD$^+$ is reduced to FADH$ _2$. 

Substrate-level phosphorylation occurs in the cytoplasm during glycolysis (e.g., conversion of 1,3-bisphosphoglycerate and phosphoenolpyruvate) and in the mitochondria during the Krebs cycle (e.g., succinyl-CoA to succinic acid). Therefore, it takes place in both cytoplasm and mitochondria.

The electrons from NADH AND FADH$ _2$ flows through the inner mitochondrial membrane, thus forming a proton gradient i.e; building an H+ pump which flows through the membrane enzyme complex. An enzyme responsible for this process and energy generation is ATP synthase.

• Chemiosmotic phosphorylation is the process where ATP is formed by the ATP synthase complex which is present in the inner membrane of the mitochondria.
• The formation of ATP by this complex takes place when 2 hydronium ions are transported across the complex from the inter membrane space down its concentration gradient.
• Thus the formation of ATP in this process takes place due to the concentration gradient that is formed by the presence of hydronium ion that is formed by the ETS Chain when the electron along with hydronium ions are transported from the NADH and FADH.
• Therefore the answer 'the establishment of an electrochemical hydrogen ion (H+) gradient' is correct.
  

• Substrate level phosphorylation is the reaction where ATP is formed by the phosphate molecule that is taken from the substrate in the reaction.
• In glycolysis during the conversion of 1,3 bisphosphoglyceric acid to 3 phosphoglyceric acid and coversion of phosphophenol to pyruvic acid; one molecule of ATP is formed during each reaction.
• In kerb cycle during the formation of succinic acid from succinyl CoA GTP is formed which is a substrate level phosphorylation, afterwards this GTP is converted to ATP in a coupled reaction.
• No substrate level phosphorylation takes place in oxidative phosphorylation or ETS
• Therefore the answer 'glycolysis and the Krebs cycle' is correct.
  

• Glycolysis is the first part of the reaction that provides substrate for the further reaction of aerobic and anaerobic reaction. IT takes place in cytoplasm and does not require any oxygen.
• LActate respiration and fermentation both are the reaction that take place in the cells or the tissues which respiration in anaerobic conditions or when there is not enough oxygen.
• Oxidative phosphorylation is the process that takes place in the in the inner mitochondrial membrane where the electrons and hydronium ions are transported through a series of complexs and at the end the electrons and hydronium are accepted by the oxygen and water is formed, this is the process in the aerobic respiration where the oxygen is used and it cannot be completed with it.
• Therefore the answer option 'Oxidative phosphorylation' is correct.
  

• In mitochondria the ETS is used for the transport of electrons and hydronium ions from inner mitochondrial membrane to the inter membrane matrix of mitochondria.
• Due to this the concentration of hydronium ions increases in the intermembrane matrix.
• The ATP synthase complex which is present in the inner membrane of the mitochrondria are used for the synthesis of ATP.
• The complex is used to transport hydronium ions from the intermembrane matrix down its concentration gradient
• For every 2 hydronium ions transported through the complex one molecule of ATP is generated.
• Therefore the transport of the H+ ions due the difference in the concentration provides direct energy for the formation of ATP.
• Therefore the correct answer is option 'a difference of H+ concentration on opposite sides of the inner mitochondrial membrane'.
  

• Electrons that are transported through the ETS are passed through various complexs of the transport chain such as complex I, cytochrome c cytochrome b, etc
• When the electrons are passed through the complexs one after the other hydrogen ions are also passed through along with it.
• After the electrons and the hydrogen have passed through the last of the complex the last acceptor of the electron in this chain will be a molecule of oxygen after reacting to which a molecule of water is formed.
• Therefore the correct answer is option 'oxygen'.
  

• Oxidation phosphorylation is the process where the electron acceptor such as NADH and FADH release their H ions and the ions and the electrons are tranported through various complexs of electron transport system.
• NADH gives electrons which pass through 5 complexs of the ETS and FADH pass through 4 complexs of the ETS 
• These electron at the end of the transport system react with oxygen and form a molecule of water.
• Where the proton which is released by the complexs of the ETS during the transport of electrons are used in formation of ATP.
• one molecule of NADH forms 3 molecules of ATP and one molecule of FADH forms 2 molecules of ATP
• So after one cycle of kerb 4 molecules of NADH are released and one molecule of FADH which results in formation of 12 ATP and 2 ATP respectively. Thus generating 14 ATP for each pyruvic acid.
• Therefore the amount of the maximum generated ATP in cellular respiration is done by oxidative phosphorylation.
• Therefore the answer option 'oxidative phosphorylation' is correct.
  

The process of oxidative phosphorylation involves the production of ATP by utilizing electrons falling from the hydrogen in glucose to the oxygen in a living cell. It does not lead to the production of carbon dioxide molecules.

Thus, the correct answer is 'Oxidative phosphorylation.'

Photophosphorylation occurs in the grana and requires the direct sunlight energy to make energy-carrier molecules that are used in the dark reaction. The light energy is trapped by chlorophyll to make ATP and NADPH. Oxidative phosphorylation is the synthesis of energy-rich ATP molecules with the help of energy liberated during oxidation of reduced co-enzymes (NADH,${FADH} _{2}$) produced in respiration.

During the oxidation of carbon atoms from complex organic food molecule, carbon dioxide is released as a waste product. The energy released from these reactions is not used up by the cells completely. Alternatively, it is converted into ATP and NADH, and this can be used throughout the cell to power metabolism and construct new cellular components. In addition, workhorse proteins called enzymes use this chemical energy to catalyze chemical reactions within the cell.

Oxidative phosphorylation is the process of formation of ATP (energy) molecules inside the plant and animal cells. It takes place inside the mitochondria. During the oxidative phosphorylation, electrons flow from NADH  or FADH to O₂ through the four different type complexes found in the inner mitochondrial membrane, which leads the pumping of the proton from outside to the matrix.

F1 is the peripheral complex for ATP synthesis, and F0 is the integral membrane protein forming the proton channel. Statements (i) and (iii) are correct.

NADH is reoxidized in a single step to form water (in the presence of oxygen). NADH to donate electrons directly to Oxygen to water. NADH to Oxygen the many-electron carriers in the electron transport chain and heat is liberated as most of the energy.

Na$^+$/K$^+$ ATPase, is a cationic pump that transports 3Na$^+$ ions to the outside, while importing 2K$^+$ against their concentration gradient. This maintains the inner membrane potential negative, In inhibition of the pump, the ions will move along their concentration gradient, reaching towards equilibrium through the leak channels that allow passive movement of these ions.

Electron transport chain includes the downhill flow of electrons to final electron acceptor through a chain of membrane-bound carriers to facilitate the uphill transport of protons across a proton-impermeable membrane. It produces proton gradient that drives transport of protons (ions) down the concentration gradient through Fo particles of ATP synthase. The proton-motive force that drives movement of protons (ions) provides the energy for ADP phosphorylation. Thus, the correct answer is option C.

NAD is a coenzyme which acts as an electron acceptor in Krebs cycle and acquires hydrogen ions to become NADH.

Oxydative phosphorylation is the process of formation of ATP as a result of transfer of electrons from NADH or FADH$ _2$ to O$ _2$. This process which takes place in mitochondria and ATP is the major source of cellular respiration.

Enzymes that catalyze oxidative phosphorylation are present in the inner membrane which is much less permeable of mitochondria. Oxidative phosphorylation is the process of electrons are transferred from electron donors to electron acceptors 

the process produces the 2 pyruvate molecule with 2 water molecule, 2 ATP, 2 NADH molecules, and 2 hydrogen ions. At the end of electron transport, oxygen is the final electron acceptor, and it combines also with hydrogen ions to form H2O. The end product of oxidative phosphorylation would be ATP molecules, which carry energy.

The hydrogen acceptor is FAD during the oxidation of Succinic acid Fumaric acid by succinate dehydrogenase.

Both the oxidative phosphorylation and photophosphorylation are in which cells make energy in the form of ATP, oxidative phosphorylation occurs during cell respiration and photophosphorylation occurs during photosynthesis. Oxygen is released during photophosphorylation and oxygen is taken up.

Iron and copper are present in cytochrome a$ _3$, Iron transfer electron to oxygen through copper, so cytochromea3 called terminal electron donor.

The electron is transferred from NADH to oxygen in mitochondria con­sists of four multi-protein complexes is coupled to the synthesis of ATP from ADP and inorganic phosphate (Pi) which is called as oxidative phosphorylation. 

NAD and FAD plays a major role in cellular respiration,  They carry the H+ and electrons to Electron Transport Chain to convert ADP + Pi ATP.

Glyceraldehyde-3-phosphate is oxidized by the coenzyme nicotinamide adenine dinucleotide (NAD). NAD+ is an oxidizing agent - it accepts electrons from other molecules and becomes reduced.

Brown adipose tissue is rich in mitochondria, containing an uncoupling protein (thermogenin) that uncouples oxidation and phosphorylation of adenosine diphosphate, reduces ATP production, and consequently enhances thermogenesis.

Proton motive force drives ATP synthesis via ATP synthase, not uniport. The other statements describe known biological processes.

Oxidative phosphorylation is the process in which ATP is formed by the transfer of electrons from NADH or FADH 2 to O 2 by a series of electron carriers. The sunlight-driven production of ATP from ADP and inorganic phosphate is called photophosphorylation.

In the Krebs cycle, succinate is oxidized to fumarate by the enzyme succinate dehydrogenase, which uses FAD as an electron acceptor.