Have you ever wondered how all living things, including humans that coexist on Earth, sustain life? There is a wide variety of organisms, and various organs perform different functions, of which energy supply to perform all these functions is very important for life to move and work. Through this article, I'm going to find out the definition of cellular respiration, how this function works, and why it's important to living things!
What is Cellular respiration?
All living things naturally use cellular respiration to convert and store organic molecules into energy. Through cellular respiration, organisms gain energy called ATP, which is also called Adenosine 5’-triphosphate and is a major molecule that stores and transfers energy to cells. The process of cellular respiration includes aerobic respiration and anaerobic respiration, where ATP is created through these two main respiration methods, and they allow the organs of life to move and perform things.
The process of cellular respiration (Aerobic and Anaerobic respiration)
In the most basic process of cellular respiration, aerobic and anaerobic respirations exist in cellular respiration, and through these two methods, ATP is generated via glycolysis, Krebs cycle, and electron transport chain.
Aerobic respiration (Glycolysis)
In the aerobic respiration process, the first step in cellular respiration is glycolysis, a process of decomposing glucose and receiving ATP energy, which is located in the cytoplasm that is a thick solution filled with each cell and surrounded by the cell membrane. In this process, one glucose molecule decomposes into two pyruvate acids without requiring oxygen. As glucose decomposes into pyruvate acid and changes, the starting molecules of glucose are rearranged and two phosphate groups adhere to them. The phosphosphate acid group destabilizes the modified glucose fructose-1,6-bisphosphate, enabling the formation of two 3-carbon sugars including a phosphosphate acid group. The phosphate used at this stage comes from ATP, so two ATP molecules are consumed. In this step, each three-carbon sugar is converted into another three-carbon molecule, pyruvate, through a series of reactions. The result provided through this process, two ATP molecules and one NADH molecule are produced in the reaction after conversion to pyruvate.
Aerobic respiration (Krebs cycle)
The Krebs cycle is the second stage of the process for aerobic reaction to take place, and is considered as the next step in glycolysis. The Krebs cycle is also known as the Citric Acid Cycle, and unlike glycolysis, the Krebs cycle is located in a matrix in an organelle called mitochondria. In the Krebs cycle, one ATP molecule, three NADH, one FADH2, two CO2, and three H+ are produced using acetyl CoA molecules. However, since acetyl CoA produces two molecules in the process, the final total number of molecules produced is doubled (2 ATP, 6 NADH, 2 FADH2, 4 CO2, and 6 H+). The results produced in the glycolysis and Krebs cycle are transferred to the last step, Electron Transport Chain (ETC).
Aerobic respiration (Electron Transport Chain)
The Electron Transport Chain, also known as oxidative phosphorylation, is the last stage of aerobic reaction, and finally produces a large amount of ATP with those produced from glycolysis and Krebs cycle, and H20 is discarded as a waste product. Unlike glycolysis and Krebs cycle, ETC reacts in the inner membrane of mitochondria. In this process, energy is provided to bind ATP using the NADH energy molecule of the Krebs cycle. NADH puts the electron in a protein called an electron carrier, and the electron carriers move the electron into their respective cycles to form ATP. At this time, a number of H+ are floating away from the electron carrier located in the inner membrane of the mitochondria organelle, and H+ is transferred under the electron carrier through diffusion. Diffusion refers to spreading from both sides, using the formula of High to Low concentration, from the side with a larger number to the side with a smaller number until the number of both sides is equal. When H+ diffuses, a concentration gradient is generated, and from this phenomenon, a protein called ATP synthase begins to make ATP. As this process continues to be repeated, approximately 34 to 36 ATP molecules are made in total. After that, the electrons in the electron carrier meet the remaining H+ and O2 floating on top to become H20, after that, it's discarded as a waste product since it's treated as a useless product.
Anaerobic respiration(Glycolysis)
Anaerobic respiration is located in the cell cytoplasm and does not require oxygen at all compared to the entire process of aerobic respiration. The first step in anaerobic respiration is glycolysis, in which glucose molecules decompose into two pyruvate acids, resulting in two ATP molecules. When oxygen is not present, as in the case of fermentation, pyruvate is converted into other by-products, and carbon dioxide is also released. In this process, two ATP molecules are produced. In anaerobic respiration, glucose decomposes when oxygen is not present, and due to this chemical reaction, ATP energy is transferred from glucose to cells. In the fermentation process, the final product is lactic acid or ethanol, and in addition to these substances, other energies in the form of ATP molecules are also produced.
Conclusion
The purpose of cellular respiration is to provide ATP, the energy needed for all cells in each organism to function, to help keep the creatures alive, and to value their lives. If there had not been a process of cellular respiration, all the creatures' lives on Earth would not produce important reactions such as digestive function, movement, and muscle contraction. Cellular respiration can be considered one of the essential processes and reactions for life to maintain and live in the future.
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