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ATP Synthesis in Mitochondria

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ATP or adenosine triphosphate provides energy to the cell or living organisms. Atp is required by the cells for different activities such as the transportation of ions, muscle contractions, and biomolecule synthesis. ATP synthesis in cellular respiration. The oxidation of respiratory substrates such as proteins, lipids, and carbohydrates produces ATP. Energy is produced during their oxidation and is then stored in ATP as high-energy bonds. 

ATP Synthesis Pathways

In ATP formation four steps are involved. Glycolysis, pyruvate oxidation, the citric acid or Krebs cycle, and oxidative phosphorylation.

Glycolysis

The process by which glucose is broken down to provide energy is known as glycolysis. It generates two pyruvate molecules, ATP, NADH, and water. There is no need for oxygen throughout the process, which occurs in the cytoplasm of a cell. Both aerobic and anaerobic organism experience it.

The first stage of cellular respiration, which takes place in all organisms, is called glycolysis. The Krebs cycle comes after glycolysis during aerobic respiration. Small amounts of ATP are produced by the cells in the absence of oxygen as fermentation follows glycolysis.

Glycolysis Pathway

Glycolysis is the process in which glucose is broken down to produce energy. It produces two molecules of pyruvate, ATP, NADH, and water. For energy-intensive activities and reactions such as protein synthesis, ion transport, and kinase-catalyzed reactions, glycolysis generates the ATP needed.

ATP Synthesis in Mitochondria

Pyruvate Oxidation

The eukaryotic cell mitochondrial matrix is the site of pyruvate oxidation. Eukaryotes are organisms that have a nucleus, nuclear envelope, and membrane-bound organelles, such as humans, other animals, plants, and fungi. Organelles are separate cellular structures that carry out particular functions, like mitochondria. The primary function of mitochondria is in the generation of energy, where processes like pyruvate oxidation and ATP synthesis take place. Possibly the most complicated organelle in a cell is the mitochondrion.

Pyruvate is a byproduct of glycolysis that is created in the cytoplasm, therefore in order to reach the mitochondrial matrix, it must pass through both the outer and inner mitochondrial membranes. What’s in the mitochondrion? 

  • An outer membrane
  • An intermembrane space
  • An inner membrane with cristae (folds)
  • A matrix

The mitochondrial matrix, the innermost region of the mitochondria, is where pyruvate oxidation occurs. Pyruvate oxidation takes place in the cytoplasm of prokaryotes (animals without a recognizable nucleus or organelles that are attached to membranes).

Citric Acid or Krebs Cycle

Hans Krebs first introduced the Tricarboxylic Acid Cycle (TCA). Coenzymes are reduced and acetyl CoA is oxidized in a multi-step enzymatic process. The mitochondrial matrix is where it happens.

It is the common pathway for the full oxidation of proteins, lipids, and carbohydrates as they are converted to acetyl coenzyme A or other cycle intermediates. The Tricarboxylic acid cycle or the Citric acid cycle receives the generated Acetyl CoA. This method completely oxidises glucose. Oxaloacetate, a 4-carbon molecule, and acetyl CoA interact to generate 6C citrate. Two molecules of CO2 are released during this procedure, and oxaloacetate is recycled. ATP and other high-energy substances like NADH and FADH2 are stores of energy.

Oxidative Phosphorylation

Electron Transport Chain

 

In the process of oxidative phosphorylation, energy is converted into ATP by a sequence of protein complexes located inside the inner membrane of mitochondria (the electron transport chain and ATP synthase).

ATP Synthase 

ATP Synthase

 

Two components make up ATP Synthase. F0 is the portion that is encased inside the mitochondrial membrane (in eukaryotes), thylakoid membrane (only in plants), or plasma membrane (in prokaryotes). The H+ ions that move across the membrane power this motor. The F1-ATPase is a component found inside the mitochondria, the stroma of the chloroplast, or within the bacterial or archaeal cell. This is yet another engine that produces ATP. It is believed that these two components were once two separate structures with two distinct roles before evolving into ATP synthase.

The F1-ATPase area is comparable to H+ motors that enable the movement of flagella, the arm-like appendages on some bacteria, while the F0 section is comparable to DNA helicases (enzymes that unzip DNA so that it can be used as a template for reproduction). ADP and Pi are converted into ATP by the central stalk and rotor of the F1-ATPase when it is spun. This is a rendering of the structure of ATP synthase. F0 is shown in blue and purple, while F1-ATPase is shown in red.

ATP Synthesis

ATP Synthesis

 

Different processes are used to produce ATP, including cellular respiration in mitochondria, photosynthesis in chloroplasts of plants, and translocation of ATP across the inner membrane of bacteria and archaea, which lack mitochondria. Although different types of organisms have different ways of producing ATP, they all use the same basic steps.

In the mitochondria of eukaryotes, the molecules of NADH and FADH2 are products of citric acid cycle, transport electrons through three separate protein complexes, and release an electron transport chain. As a result, energy is released, and this energy enables protons (H+ ions) to move through protein complexes that serve as proton pumps and down a proton gradient. The rotor and stalk of the ATP synthase are turned by the flow of these protons down the gradient, allowing a phosphate group to combine with adenosine diphosphate (ADP) to produce ATP.

Similar processes occur in chloroplasts, with the exception that light energy is used to excite electrons, which causes them to move along the electron transport chain and allow H+ ions to pass through a membrane. Since the ability to produce ATP was present in the common ancestor of all living things, these techniques are similar in a variety of very different organisms.

FAQs on the Process of ATP Synthesis

Question 1: What is the full form of ATP? 

Answer: 

ATP (Adenosine triphosphate). 

Question 2: In the Krebs Cycle, How Many ATPs are produced? 

Answer:

In one Krebs Cycle, two ATPs are generated. The Krebs cycle produces 4 CO2, 6 NADH, 2 FADH2, and 2 ATPs for fully oxidizing a glucose molecule.

Question 3: How Many NADH are Produced In The Krebs Cycle?

Answer:

Three molecules of NADH are created during one cycle of the Krebs cycle. A glucose molecule will produce 4 CO2, 6 NADH, 2 FADH2, and 2 ATPs via the Krebs cycle.

Question 4: How is ATP synthesized in mitochondria?

Answer:

Through oxidative phosphorylation in the mitochondria, the majority of the adenosine triphosphate (ATP) created during glucose metabolism is produced. This intricate reaction is driven by the proton gradient produced by mitochondrial respiration across the inner membrane of the cell.

Question 5: What is glycolysis? 

Answer: 

Glycolysis is the process in which glucose is broken down to produce energy.



Last Updated : 12 Jan, 2024
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