Cellular Respiration
Cellular respiration is my least favorite subject that I have encountered thus far in biology. It includes many complex formulas and has many processes that work together to help make it work. Cellular Respiration - The series of reactions inside your cells that helps to break down energy-containing molecules to provide your body with energy. This may sound simple, but it actually invloves several separate steps.
The first step in this cycle is called Glycolosis. In this process, glucose molecules are broken down into two molecules of pyruvic acid plus a small amount (2) of ATP and NADH. Below is a diagram that illustrates the process. (By the way, I made it myself)
The first step in this cycle is called Glycolosis. In this process, glucose molecules are broken down into two molecules of pyruvic acid plus a small amount (2) of ATP and NADH. Below is a diagram that illustrates the process. (By the way, I made it myself)
Ok. So now let's break this down into simple steps. We start with one molecule of Glucose (C6H12O6) that is combined with the phosphates of 2 ATP molecules (Yeah that is supposed to be a P at the end of that ATD there). This forms one six-carbon compound that immadietly breaks down into two 3-Carbon compounds. From here, 2 Molecules of NAD+ are added to other products form this reaction to form 2 molecules of NADH and 2 Hydrogen ions, or essentially protons. Then, the two phosphates from the ATPs that were converted to ADP at the beginning of the reaction are added to 4 molecules of ADP that are created, making 4 molecules of ATP. Also, during the process, 2 molecules of water are also created. The pyruvic acid that is created is then used in other processes to further release additional energy.
Following glycolosis, cellular respiration can take one of three routes. If oxygen is not present, it goes through a process called fermentation. Fermentation is an anaerobic process, which means that it does not need oxygen to proceed. During fermentation, no ATP or energy is produced but the NADH produced in glycolosis is recycled to form more NAD+ so that glycolosis can continue. Depending on the kind of cell used, either lactic acid fermentation or ethyl alcohol fermentation will take place. In humans, we do lactic acid fermentation. However, in some species of yeast of other organisms, ethyl alcohol fermentation takes place. Both processes are very similar and have many of the same products, however, aside for the differences between the lactic acid and the ethyl alcohol. However, both serve to turn NADH into NAD+ and so restart the process of glycolosis.
When oxygen is present, aerobic processes take place. These reactions require oxygen and are much more effective at releasing energy than anaerobic reactions. Reactions that are categorized as aerobic include the Krebs cycle and the Electron Transport Chain.
When oxygen is present, aerobic processes take place. These reactions require oxygen and are much more effective at releasing energy than anaerobic reactions. Reactions that are categorized as aerobic include the Krebs cycle and the Electron Transport Chain.
Anaerobic Processes
This section will detail the processes of lactic acid fermentation and ethyl alcohol fermentation. Lactic Acid Fermentation is the process that takes place in humans and many other organisms that is a simple way of replacing molecules needed to restart glycolosis.
Lactic Acid Fermentation
In this process, an enzyme converts the pyruvic acid made in glycosis into a three-carbon molecule called lactic acid. Also, at the same time, one hydrogen atom is added to NADH to form NAD+ which is used to restart glycolosis. At the same time, a proton (H+) is added to pyruvic acid.
Although this process is simple, it provides no energy directly but rather resets the raw materials needed to get glycolosis started again. Because of this, it is not able to supply all the energy needed by complex organisms to survive, including almost all multi-cellular organisms. Instead, aerobic respiration is used in combination with this to provide energy more efficiently.
This process is what causes your muscles to burn after exerting yourself. As lactic acid builds up inside your cells, it creates the "burning" sensation that you feel until it can dissipate.
Although this process is simple, it provides no energy directly but rather resets the raw materials needed to get glycolosis started again. Because of this, it is not able to supply all the energy needed by complex organisms to survive, including almost all multi-cellular organisms. Instead, aerobic respiration is used in combination with this to provide energy more efficiently.
This process is what causes your muscles to burn after exerting yourself. As lactic acid builds up inside your cells, it creates the "burning" sensation that you feel until it can dissipate.
Ethyl Alcohol Fermentation is very similar to lactic acid fermentation in purpose and process. However, there are a few differences in the process as shown below:
Ethyl Alcohol Fermentation
In this reaction, one molecule of CO2 is released form the molecule of pyruvic acid and released outside. (This causes the bubbles that form inside of bread when it cooks). This leaves a two-carbon compound. Then, two hydrogen atoms are added to that molecule, forming Ethyl Alcohol. At the same time, the NADH changes into NAD+ using the same process as lactic acid fermentation.
Aerobic Respiration
Aerobic Respiration is one of the most complex processes in biology, but I think I said that already... Anyway, there are two sub-processes that make up aerobic respiration. They are called the Krebs Cycle and the Electron Transport Chain. There processes happen inside the mitochondria of cells. The mitochondria have inside them folds of membranes called christae which help to increase the surface area that the organelle has to undergo the reactions that are used in aerobic respiration.
Preparing the Krebs Cycle
The Krebs cycle does not produce much ATP by itself but rather makes it possible for the Electron Transport Chain to happen. To begin this cycle, pyruvic acid along with a molecule of CoA formed during glycolosis is broken down into a molecule called Acetyl CoA. During this, a molecule of NAD+ is used and converted to NADH and one H+. Also, one molecule of CO2 is released during this process. This is part of the source of the CO2 that we release when we breathe. However, as this step itself doesn't use oxygen, it isn't considered aerobic. The CoA that is used is in this reaction is recreated during the Krebs cycle by combining Acetyl CoA with a molecule of Citric Acid.
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The Krebs Cycle
Ahh, the Krebs Cycle. VERY complicated. The diagram is shown at right. As you can see, it starts with on molecule of Acetyl CoA and one molecule of Citric Acid. The Acetyl CoA is produced in the reaction shown above in the previous section. When these two molecules combine, they form a molecule of CoA which is used to restart the same before-mentioned reaction. This also causes the Citric Acid to change into a 5-carbon compound, releasing CO2 and converting one molecule of NAD+ into a molecule of NADH and a H+. Then that compound releases a CO2 while again processing a NAD+ into a NADH and a H+ and making an ADP + Phosphate into a molecule of ATP. This forms a 4-carbon compound which changes into a different 4-carbon compound while changing a molecule of FAD into a molecule of FADH+. Finally, this second 4-carbon compound changes into a molecule of Oxaelocetic Acid after converting a molecule of NAD+ into a molecule of NADH + H+. The main product of this reaction is the Oxaecetic acid that is used in the ETC. This is detailed below.
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Diagram of the Krebs Cycle |
Electron Transport Chain (ETC)
The ETC takes place in the mitochondrial matrix, another name for the spaces between the membranes of the christae. This reaction is responsible for making the vast majority of all the ATP made during Cellular Respiration. Though the name and process bear some semblance to the ETC used in photosynthesis, it is in fact an entirely different process.