As human beings we often don’t realize how hard our human bodies work when it comes to daily processes, Instantaneously, our bodies are able to: circulate blood from head to toe, create necessary enzymes to process information, and most importantly: the human body goes through the tremendous process of allocating oxygen in a way most useful for us While the human body has different mechanisms that allow us to harness oxygen into energy, there are a couple of fail-safes that kick in if oxygen is not available Cellular respiration can be split into two main categories: aerobic and anaerobic (respiration with and without oxygen respectively). Within these two categories, cellular respiration can be broken down into three phases: Glycolysis, the Krebs cycle (formally known as the Citric Acid Cycle), and the Electron Transport Chain.
While many people are under the misconception that these processes take place in the lungs, that is not the case; Glycolysis takes place in the cytosol while the other two processes take place in the mitochondria (more specifically Citric Acid Cycle in the mitochondrial matrix, and Electron Transport in the inner membrane of the mitochondria) The biggest controversy surrounding cellular respiration is the fact that there seems to be a positive correlation between the growths of tumors and the rate at which Glycolysis takes place This is because tumors and Glycolysis need to generate energy in the form of adenosine triphosphate in order to sustain themselves. The implication with this is that since one of the ways to destroy tumors is by prohibiting them to create energy you can indirectly impede the process of Glycolysis, which can put the body in imminent danger.
One pathway of cellular respiration can be described as anaerobic Anaerobic respiration starts off with the process of Glycolysis (it is important to note that Glycolysis can occur with or without oxygen, that will determine what process will occur after Glycolysis). Essentially, this process is the opposite of photosynthesis, Instead of ending up with a sugar, we start off with one. In its Latin roots, Glycolysis literally means the breaking down of sugars, Glycolysis starts off when the first molecule of glucose is present and ready to be transformed. In the first step of Glycolysis, the enzyme hexokinase comes into contact with the six-carbon glucose and phosphorylates it. Phosphorylation is the process in which a phosphate group is added to a chemical structure; imagine a set of Lego blocks attached together and one more (phosphate group) is connected on. This allows for a phosphate group to be transferred from ATP to the glucose (a Lego block moved from one figure to another), subsequently turning the ATP into ADR.
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Next, the enzyme phosphoglucoisomerase rearranges the chemical structure of glucose six» phosphate into an isomer fructose six-phosphate lsomers are exact duplicates in molecular formula but have different chemical alignments To better visualize this process, imagine 10 Legos connected together, then imagine you take the 10 Legos apart and put them back together so they form a completely different looking figures The next step is to transfer another phosphate group to the fructose six—phosphates This is done by using a phosphate from a new ATP molecule and displacing it to fructose six- phosphate, thus creating fructose one, six-biphosphatei The fourth step includes the enzyme aldolase. Aldolase is an enzyme that has the ability to split fructose one, six-biphosphate into isomers: dihydroxyacetone phosphate and glyceraldehyde phosphate Step 5 runs directly into conjunction with step 4.
‘ The enzyme triose phosphate isomerase strategically converts dihydroxyacetone phosphate to glyceraldehyde phosphate. It is important to note that equilibrium between the two molecules is not reached; if equilibrium were to be reached, Glycolysis would have enough energy to end at step 5. Triose phosphate dehydrogenase plays a major role in the 6‘” step First, it transfers hydrogen ions from glyceraldehyde phosphate to NAD‘ to form NADH (think about transferring Lego blocks), This step is essential to ensure that NADH can be used in a different phase of cellular respiration. The second crucial step is adding a phosphate group from the cytosol to the already oxidized glyceraldehyde phosphate forming one, three-biphosphoglycerate, The neXt few steps are essential because they replenish the phosphate from the ATP used in the first couple of steps; without this, Glycolysis would not continue in a perpetual cycle.
Step 7 makes use of the enzyme phosphoglycerokinase. It allows for the transfer a phosphate from each of the one, three» bisphosphoglycerate to ADP creating ATP for more cycles of Glycolysis, Next, phosphoglyceromutase displaces a phosphate from three-phosphoglycerate moving it from the third carbon in the arrangement to the second (imagine the top Lego block is blue and represents phosphate, then you move it to the middle). The 9‘” step also includes a rearrangement of molecules; enolase cleaves a molecule of water from two-phosphoglycerate to create phosphoenolpyruvic acid (keep in mind this happens to each of the two molecules) Lastly, to complete the first cycle of Glycolysis, the enzyme pyruvate kinase transfers a phosphate group fromphosphoenolpyruvic acid to ADP, which forms two molecules of pyruvic acid and 2 ATP molecules Now that Glycolysis has ended, cellular respiration can take on one of two paths as mentioned previously.
The path without any oxygen is called anaerobic respiration, and the path including oxygen called aerobic respiration, When oxygen is not present, pyruvic acid can be routed to fermentation: lactic acid fermentation, or alcohol fermentation The drawback of this is that minimal ATP is created and thus the processes are not sustainable for the long run, if it does last for a long time the cell will die. Since humans do not produce alcohol, when oxygen is not present cells go straight into producing lactic acid Alcohol fermentation (in many other organisms) is the formation of alcohol from pyruvic acid Some organisms, includingyeast, are able to go further and produce ethanolia much more concentrated alcoholr Humans form lactic acid in muscles when oxygen is depleted, such as during strenuous exercise, Lactic acid causes muscle stiffness; this mechanism is to deter any muscle movement to ensure that body is not depleted of the little oxygen it has left.
When oxygen is present, pyruvic acid will go under alternative routes—the Citric Acid Cycle, and Electron Transport. The Citric Acid Cycle has three main phases that can be broken up into 8 steps, all of which lead up to the formation of Before the cycle can begin, carbon dioxide is enzymatically exercised from each of the pyruvic acid molecules to form acetic acid. Also, acetyl coenzyme A is produced. Thus, the cycle can begin. The first step occurs when acetic acid part of acetyl CoA is combined with oxaloacetate to form citrate Acetyl coenzyme A serves as a medium of acetic acid. Coenzyme A is also released by hydrolysis, the process in which water acts as an agent to break something down, so that later it can combine with another acetic acid The second step includes the isomeration of citric acid, this allows for a hydroxyl group and hydrogen molecule to be removed from citrate.
Also, isocitrate is formed (an isomer) The third step includes the act of oxidizing isocitrate by NAD. Subsequently, the NAD is chemically reduced to form NADH, which leaves with another hydrogen molecule. The next few steps are very essential to make sure the cycle continues The fourth step includes a molecule of NAD to be reduced to form NADH and leaves with another cleaved hydrogen atom. This causes a carbonyl group to be released as an atom of carbon dioxide; eventually a molecule of succinyl-coenzyme A is created This sets the stage for a very important step. Next, when a water molecule loses its hydrogen atom to coenzyme A, a phosphate group from the cytosol forms a bond with the succinyl complexi imagine a straw put inside of a juice box, GDP is now able to turn to GTP, leaving around a succinate molecule. The sixth step is probably one of the most important.
Succinate is oxidized by a molecule of FAD, which removes two hydrogen atoms from Succinate forcing a strong double bond between two carbons forming a molecule of fumarate. This is so important because it replenishes energy molecules needed for future cycles. The second to last step includes the combination of water and fumarate to create malater The last step includes the oxidation of malate by NAD. A carbon is now transformed into a carbonyl group. The end products oxaloacetate, which can then be reused in future cycles of the Citric Acid Cycle, and 2 ATP molecules, If the only ATP that is gainedwere the two from Glycolysis and two from the Krebs cycle, we would die.
Our body needs much more energy to maintain all the processes in our body, especially for the process of cellular respiration. The majority of energy is gained in the Electron Transport Chain (ETC), anywhere from 32-34 ATE In essence, the ETC is full of multiple complexes which electrons cascade down, sort of like a marble rolling down multiple steps. Each bounce allows for an electrochemical gradient to form, thus creating energy. The most important thing to note is that the final electron acceptor is oxygen, Oxygen serves as a medium to drive the proton gradient to maximize the output of energy, thus completing one cycle of respiration and creating a byproduct of watert A process like respiration may seem rudimentary on the surface, but deep below there are a plethora of different cycles and chemical reactions taking place.
The optimal situation is that oxygen is present so respiration can go on to the phases of the Citric Acid Cycle, and later to ETC, With a mechanism so crucial there come very detrimental ramifications if anything were to go wrong For example, if an enzyme were to malfunction during the early stages of Glycolysis, all of the subsequent processes would be impeded and virtually no ATP would be made, thus leading to the demise of the cell. Another potential hazard are poisons that can disrupt cellular respiration, For example, if a human digests cyanide (found in small amounts in the seeds of fruits) the ETC can be stopped immediately, Cyanide strategically halts the proton gradient created in the ETC Haiting the proton gradient stops the production of ATP and thus also signals the demise of celli.
