As you sit here reading this article, your body is going through a series of steps to give you the energy you need to live. As you blink, think, breathe, walk and talk, your body uses this energy it gets from the food you eat. Let's take Gerald as an example. Gerald just ate an apple. His body will take glucose from this apple and extract the energy contained in the glucose through a series of reactions called cellular respiration. Without cellular respiration Gerald would have died. The four phases of cellular respiration are glycolysis, the formation of acetyl CoA, the Krebs cycle, and the electron transport chain. By tracking electrons in cellular respiration we can understand how Gerald's apple, in part, gives him the energy to survive. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Cellular respiration begins in glycolysis. Glycolysis breaks down a glucose molecule to absorb the energy stored in its bonds. This glucose molecule comes from the food we eat. For example, when Gerald eats his apple, the glucose from that apple will begin to be broken down in glycolysis. Now this glucose molecule will travel outside the mitochondria, or into the cytoplasm of the cell, to begin the process. First the glucose molecule will be rearranged and using two ATP will add a phosphate on both sides. This molecule is called fructose-1-6-biphosphate. Due to the fact that this molecule is unstable, it splits into two three carbon compounds with a phosphate on each. Subsequently these two three carbon compounds are transformed into pyruvate. In this process, for each pyruvate, two molecules of ATP and one of NADH are produced. ATP is produced when a phosphate is added to an ADP, while NADH is produced when an h+ is added to a NAD+. This means that an electron is added to NAD+. This NADH will later be used in the electron transport chain which produces more ATP. Since two ATPs were used in the early stages of glycolysis, the final product of glycolysis produces 2 ATP, 2 NADH, and 2 pyruvate. The breaking of glucose bonds and the cleavage of fructose-1-6-bisphosphatase releases electrons that are captured by ATP and NADH. These electrons then move on to the next stage of cellular respiration which is the formation of acetyl CoA. The next step in cellular respiration is the formation of acetyl CoA. In this phase the pyruvate produced in glycolysis moves into the matrix of the mitochondria. To begin this phase, pyruvate loses a carbon that forms a two-carbon compound called acetyl. When pyruvate loses a carbon it releases CO2. Due to the fact that a bond has been broken to take away this CO2, electrons are released. These electrons are collected and NAD+ and NADH+H+ are formed. According to the article What is the Difference Between NAD+ and NADH, “First, a charged hydrogen molecule (H+) and then two electrons. Since the electrons are negatively charged, the combination of positively charged NAD+ and H+, paired with two electrons, cancel each other out and neutralize the resulting NADH molecule. Once the 2-carbon compound is produced, coenzyme A is added to the acetyl making acetyl CoA. the coenzyme is added to the acetyl to allow it to move across the two membranes of the mitochondria and into its matrix where the remaining phases of cellular respiration will take place. Once the acetyl CoA enters the mitochondria, the coenzyme leaves and you are now left with the two carbon compounds. The purpose of this coenzyme was to block H+to bind to acetyl. Because it was just a holding point, the bond between the acetyl and the coenzyme is very weak, meaning not much energy is stored. In summary, the purpose of this phase of cellular respiration was to cause the two to move the two carbon compounds made up of pyruvate into the mitochondria allowing them to be used for the next phase of cellular respiration, the Krebs cycle. The Krebs cycle begins when acetyl is attached to a four-carbon compound called oxaloacetate. The product of this event is a molecule called citrate. Citrate is a six-carbon compound and is the first product of the Krebs cycle (the previous two sentences were paraphrased from the Krebs cycle worksheet). This is explained in the article Pyruvate oxidation and the citric acid cycle published on LumenLearning.com. “Unlike glycolysis, the citric acid cycle is a closed circuit: the last part of the path regenerates the compound used in the first phase. The eight steps of the cycle are a series of redox, dehydration, hydration and decarboxylation reactions that produce two molecules of carbon dioxide, one GTP/ATP and reduced forms of NADH and FADH2. The Kreb cycle is also considered an aerobic cycle because it requires oxygen. This cycle requires oxygen because “the NADH and FADH2 produced must transfer their electrons to the next path in the system, which will use oxygen.” as explained in the previously used article, Pyruvate Oxidation and the Citric Acid Cycle. Once citrate is formed, the bond between one carbon breaks and electrons and CO2 are released. These electrons are collected by a NADH. This NADH will be used in other phases of cellular respiration by providing its electrons as energy. Once this step is complete, we are left with a five-carbon compound. This five-carbon compound then breaks another bond, releasing more energy and releasing more CO2. When this happens, a NAD+ and an ADP collect these electrons forming a molecule of NADH and a molecule of ATP. They will subsequently be used to provide energy for further stages of cellular respiration. After the second CO2 has been separated, succinate remains which is a four-carbon compound. The next step in the Krebs cycle is to convert succinate to oxaloacetate. To do this, succinate must first transform into fumarate which is an enzyme. To do this, succinate transfers two hydrogens to a carrier protein called FAD which subsequently creates FADH2. FADH is a transporter protein very similar to NADH, however it has some unique characteristics. According to the article Oxidation of Pyruvate and The Citric Acid Cycle, “The energy contained in the electrons of these atoms is insufficient to reduce NAD+ but adequate to reduce FAD. Unlike NADH, this transporter remains attached to the enzyme and directly transfers electrons to the electron transport chain.” Once fumarate is produced, it is transformed into malate. This occurs when water is added to the fumarate. In the last step the malate is converted back into oxaloacetate. This is done by oxidizing the malate. Now the cycle has been completed. However, the Kreb cycle must repeat itself once again, since for each pyruvate the cycle goes around twice. This means that at the end of these two cycles you would have created 6 NADH, 2 FADH, 2ATP and 4CO2. NADH, FADH and ATP are all responsible for transporting electrons from the Krebs cycle. These electrons obtained from the breaking of high-energy bonds will be used during the phases of cellular respiration so that the cell has enough energy to complete these phases. The FADH and part of the NADH will now move directly.