Cellular respiration and fermentation

Published: 2021-06-24 21:15:04
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In this experiment, the subjects of study were fermentation, mitochondrial respiration, and redox reactions. In the first experiment, yeast was grown in various carbohydrate solutions at various temperatures. In the second experiment, succinate was added to various samples of a mitchondrial suspension, DPIP, and a buffer. Then after two blanks were used, the samples were placed into the spectrophotometer for transmittance testing. Introduction Cellular respiration is a group of reactions that occur when a cell turns the energy from food and nutrient sources into ATP, releasing the rest of the products as waste.
It is a catabolic set oreactions and they are defined as being exothermic redox reactions, meaning that energy is released and electrons are transferred. It takes place in the mitochondrial matrix within the cells. [3] Fermentation is an anaerobic, or lacking oxygen, reaction in which pyruvate is metabolized, NADH is oxidized to NAD+, and waste products are taken out so glycolysis can reoccur. Both of these processes are very significant for organisms because they are how organisms create their energy.
Without these pathways, nutrients would not be converted to energy and the organism would be unable to do much of anything. Plants, animals, bacteria, fungi, and algae all use cellular repiration while fermentation is mostly used by plants and fungi, though lactic acid fermentation does occur in animals and in bacteria. In cellular respiration, glucose is the starting molecule which then undergoes glycolysis and is split into 2 pyruvate molecules. Oxygen is the final electron acceptor in the electron transport chain, meaning the ETC couldn’t occur without oxygen and cellular respiration could not be completed.
Carbon dioxide is a product of cellular respiration and is released by the organism. In fermentation, glucose is again the initial molecule before glycolysis is performed, breaking the glucose down into pyruvic acid. But then, without any oxygen to use for cellular respiration, fermentation begins and pyruvate is converted to either lactic acid or alcohol. So oxygen doesn’t have a role in fermentation. Carbon dioxide however, is a product of fermentation, along with alcohol, when pyruvate becomes unstable and splits.
Carbohydrates are split into 3 main categories: monosaccharides, disaccharides, and polysaccharides. Monosaccharides are known as simple sugars, because of their simplicity in structure as opposed to its di- and poly- counterparts. Monosaccharides serve primarily as energy for organisms, as it can be broken down into carbon dioxide and water when in the presence of oxygen and energy is released. They also serve as “building blocks” for forming di- and polysaccharides. [1] Disaccharides are two monosaccharides that are bonded covalently.
They serve primarily as a food source for monosaccharides and are in most food items that contain sugar. Polysaccharides are polymers of glucose (monosaccharide) and function primarily as an easy to access source of energy for an organism. The two major polysaccharides are starch and glycogen. Glycogen is stored in an organism when excess glucose is consumed. The glycogen is kept as an energy store so that at a later time when needed, it can be easily accessed and converted to glucose. Redox reactions are reactions in which oxygen is gained (oxidation) and/or lost (reduction).
Redox reactions play a critical role in the citric acid cycle because without the reduction of NAD+ to NADH, NADH couldn’t be sent to the electron transport chain, meaning the final stage of respiration couldn’t be completed and less energy would be created and made available to the organism. Also, FAD is used in the succinate/fumarate oxidation reaction as a prosthetic group in the enzyme, responsible for about 1. 5 ATP molecules’ worth of energy. [2] DPIP is used in the experiment as a visual aid to see the oxidation of succinate occuring.
This is due to the fact that DPIP intercepts the hydrogen ions that succinate releases and changes from oxidized to reduced, going from blue in color to colorless in the process. The goal of this experiment is to successfully stage and observe redox reactions in mitochondrial respiration and fermentation, to better understand these processes. As for hypothesizing, prior to the lab I thought that glucose at 37 degrees would be the greatest yield of CO2 and that as time went on, the transmittance readings of the reduced DPIP would decrease.
Neither was entirely correct. Sucrose at 37 degrees seemed to yield the most CO2 and the results for the transmittance readings of the reduced DPIP varied by sample. Methods and Materials Fermentation In part one of the experiment, saturated starch and 4 degrees celsius were the assigned food source and temperature respectively. .5g of yeast was added to 15 mL of the solution, which was immediately transferred into a fermentation tube and stored in the refrigerator with the rest of the 4 degrees samples.
Fermentation was then allowed to occur for 40 minutes, with the amount of CO2 produced recorded every 5 minutes. CO2 was measured by reading the level as compared to the markings on the fermentation tube. Mitochondrial respiration/Citric acid cycle In part two of the experiment, the spectrophotometer was turned on and set to read the % transmittance of 600 nm wavelength light. 6 cuvettes were then obtained and labeled B-1 and B-2 (to be used as blanks) as well as 1, 2, 3, and 4 for the four samples. Parafilm was then cut out to cover the tops of the cuvettes.
The blanks and samples were set up according to Table 9. 1, which is included at the end of this section. Blank 1 was then used for the first three samples containing mitochondria while Blank 2 was used for sample 4 which did not have mitochondria. The cuvettes were then given the proper amount of succinate and then shaken with parafilm over the top to mix the components. The spectrophotometer was then blanked by B-1 and the readings for samples 1, 2, and 3 were successively recorded at 5 minute intervals.
Shortly thereafter the spectrophotometer was then blanked by B-2 for sample 4 which also had its readings recorded at 5 minute intervals. Results The results of the first part of the experiment, the fermentation section, show that sucrose was the most efficient food source in terms of CO2 production. The results also show that as the temperature is raised, to 37 degrees, for example, CO2 production increases. So of the food sources: glucose, sucrose, and starch and the testing temperatures: 4, 25, and 37 degrees, the results show that at 37 degrees with sucrose the msot CO2 was produced.
This data can be found in Table 1. In part two of the experiment, samples 2 and 3 had steadily increasing transmittance readings of reduced DPIP while sample 1 slightly decreased and sample 4 essentially stayed constand with a slight decrease. This data can be found in Table 2. Table 1: mL of CO2 produced with varying food sources and temperatures Table 2: % transmittance readings of reduced DPIP samples over time Table 3: Reaction rate with varying succinate concentrations Graph 1: % transmittance readings of reduced DPIP over time Discussion
The findings of this experiment confirm that in the case of fermentation, sucrose and glucose were better food sources in terms of CO2 production, while in the mitochondrial respiration portion, DPIP was found to be reduced and when the succinate was added, it was oxidized and fumarate was formed. This of course in turn reduced the DPIP which allowed for a visual aid to show the oxidation of succinate. As for concluding each portion, the major conclusion of part one was stated above, that sucrose and glucose are better food sources than starch, and the only source for which 37 degrees didn’t yield the most CO2 was starch.
Part two can be concluded by stating that the experiment was successful as succinate was oxidized, shown visually by the DPIP’s loss of color. Potential sources for error were scarce but it’s possible that other lab members could have tampered with samples while in the refrigerator or what have you. The amount of CO2 varied quite a bite among food sources, as well as temperature. This could be due to the complexity of the carbohydrates, with sucrose being more readily available to use in fermentation etc. One control did produce CO2 which could likely be attributed to the temperature.
Succinate was necessary to the reduction of DPIP, which is because succinate releases hydrogen ions that DPIP intercepts and is reduced by. The mitochondria were respiring because the reduction of DPIP and in turn the oxidation of succinate was visible. Oxidation is the gain of oxygen while reduction is the loss of it. The results may have been different with mouse muscle mitochondria as opposed to lima beans because the mitochondria in mouse muscle would be responsible for doing more work and might respire more efficiently.

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