Fermentation products like ethanol still contains some C-H bonds that can be oxidized.
Electron Transport Chain
The electron transport chain, also known as the electron transport system, is a group of proteins that transfer electrons through a membrane within mitochondria to create a gradient of protons that drives adenosine triphosphate (ATP)synthesis. The cell uses ATP as an energy source for metabolic processes and cellular functions. ETC involves series of reactions that convert redox energy from NADH (nicotinamide adenine dinucleotide (NAD) + hydrogen (H)) and FADH2(flavin adenine dinucleotide (FAD)) oxidation into proton-motive force(PMF), which is then used to synthesize ATP through conformational changes in the ATP synthase complex, a process known as oxidative phosphorylation.
Metabolism
Picture a campfire. It keeps the body warm on a cold night and provides light. To ensure that the fire keeps burning, fuel needs to be added(pieces of wood in this case). When a small piece is added, the fire burns bright for a bit and then dies down unless more wood is added. But, if too many pieces are placed at a time, the fire escalates and burns for a longer time, without actually burning away all the pieces that have been added. Many of them, especially the larger chunks or damp pieces, remain unburnt.
Cellular Respiration
Cellular respiration is the cellular process involved in the generation of adenosine triphosphate (ATP) molecules from the organic nutritional source obtained from the diet. It is a universal process observed in all types of life forms. The glucose (chemical formula C6H12O6) molecules are the preferred raw material for cell respiration as it possesses a simple structure and is highly efficient in nature.
Fermentation is the process in which glucose is metabolized under anaerobic conditions to produce ethanol/ lactic acid, CO2, and H2O as byproducts. It is the quick means of generation of ATP than oxidative phosphorylation. In all fermentations, the ratio of Hydrogen/Carbon atoms present in reactants and products is the same. In microorganisms, fermentation is popularly called alcoholic fermentation where alcohol is the main product of glucose metabolism. Whereas in muscle cells lactic acid fermentation takes place where lactic acid is the main product of fermentation. Reducing equivalent NADH act as a hydrogen carrier and an energy source. Fermentation occurs in two steps.
- First, Pyruvate produced from glucose through glycolysis is converted to acetaldehyde in the presence of complex enzyme Pyruvate decarboxylase which requires cofactor TPP (Thiamine pyrophosphate).
- Secondly, Acetaldehyde is then reduced to alcohol in the presence of enzyme alcohol dehydrogenase. This enzyme facilitates the transfer of hydride from NADH to Acetaldehyde leading to the formation of alcohol. It is this CH bond of ethanol which is highly flexible to facilitate reversible reactions of conversion of ethanol to acetaldehyde and then acetic acid.
- GlucosePyruvate Acetaldehyde Ethanol+CO2 + H2O
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