Task 4 ii) Cellular respiration is considered as controlled combustion. This is when cells that are not related to photosynthesis obtain their energy by oxidizing food molecules such as carbohydrates into carbon dioxide. ATP is formed when the energy difference between food molecules and carbon dioxide is used. There are three phases in cellular respiration. Glycolysis, Krebs cycle and respiratory electron transport system. Glycolysis is a succession of chemical reactions that take place within the cell's cytosol. The entire process is controlled by enzymes. The cytosol is the watery part of the cytoplasm in a cell. Glycolysis is anaerobic respiration. The first step involves breaking down glucose. Phosphate groups are added to glucose to make it a six-carbon ring phosphate sugar. For this to happen, 2 ATP is needed, which gives energy to glucose. The glucose is now more reactive and so this six-carbon sugar phosphate is then broken down, forming two, three carbon phosphates. From these two phosphates the hydrogen is subtracted and transferred to the 2 NADS which are reduced. The two phosphates called triose phosphates have now been converted to pyruvate and produced 2 molecules of ATP.4 ATP came out of glycolysis, but 2 ATP as an overall net gain, along with 2 NADH + H+. (HallyHosting, n.d.) The next stage of glycolysis occurs in the cytoplasm of the mitochondria. This is called a linking reaction, also known as oxidative carboxylation. Oxygen is needed at this stage, as is aerobic respiration and completes the conversion of pyruvate. The 2 molecules of pyruvic acid, also known as pyruvate, enter the mitochondria, where hydrogen and carbon dioxide are removed from them creating... ... middle of paper ...... oup to add to ADP . This then forms ATP. NADH+H is an electron carrier. It gives an electron to the chain, specifically to the first protein. This protein, which is NADH-Q reductase, is then ultimately reduced. It then oxidizes with the next protein reducing itself. This continues down the chain until all the proteins are reduced and oxidized. When this happens, all the collected electrons reduce the terminal electron acceptor. This is oxygen. Reduced oxygen produces water. Gradually reducing all proteins produces energy gradually. Protons are transported across the membrane in this way. Overall, once glycolysis and cellular respiration occurred, 36 ATP were produced and glucose was completely oxidized. Each step of the process occurs through enzyme control, making it a controlled combustion process.