cellular respiration in yeast, Essays (high school) of Biology

Download cellular respiration in yeast and more Essays (high school) Biology in PDF only on Docsity! ABSTRACT The effect of inorganic cofactor such as Magnesium to the rate of respiration of yeast was determined using Durham tube assembly with the substrate glucose. After thirty minutes, the test tube with the cofactor in the form of Magnesium sulphate MgSO4 showed the higher amount of carbon dioxide evolved which was measurable through volume and was one of the by- products of cellular respiration. This stated that the higher amount of CO2 evolved, the higher the rate of respiration. Thus, the hypothesis “If enzymes need cofactors to speed up its function, cofactors affect the rate of cellular respiration.” was accepted. Smith fermentation tube assembly containing 15 ml of 10% yeast concentration with different substrates was used to test the hypothesis “If the nature of substrates affects the cellular respiration in yeast, then the simpler the substrates the faster the cellular respiration.” The height of the area of the tube occupied by CO2 was measured to get the volume after thirty minutes. The result showed that sucrose had evolved the greatest CO2, followed by fructose, glucose and starch respectively while lactose and distilled water got no CO2 evolved. Thus, the result concluded the before mentioned hypothesis. INTRODUCTION Cellular respiration is a process in which cells produce the energy they need to survive. Cells use oxygen to break down the sugar glucose and store its energy in molecules of adenosine triphosphate (ATP). Cellular respiration is critical for the survival of most organisms because the energy in glucose cannot be used by cells until it is stored in ATP. Two critical ingredients required for cellular respiration are glucose and oxygen. Although most organisms on Earth carry out cellular respiration to generate ATP, a few rely on alternative pathways to make this vital molecule. These pathways are anaerobic—that is, they do not require oxygen. Fermentation is a type of anaerobic pathway used by certain species of bacteria that live in anaerobic environments, such as stagnant ponds or decaying vegetation. Some cells produce ATP using both anaerobic and aerobic pathways(Lagunzad, 2004). For example, muscle cells typically carry out cellular respiration, but if they do not receive enough oxygen, as can occur during strenuous exercise, muscles switch to fermentation. In this paper, yeast cells, unicellular microorganisms, are used as the working organisms to determine the effect of cofactors and substrates on the rate of respiration. They carry out both pathways, depending on whether they are in an aerobic environment, such as soil, or an anaerobic one, such as inside a wet lump of dough. Figure 1. The structure of unicellular organism, yeast Cellular respiration was catalyzed by enzymes. Cofactors, mostly metal ions or coenzymes, are inorganic and organic chemicals that assist enzymes during the catalysis of reactions. In the performed experiment the cofactor used was Magnesium in the form of Magnesium sulfate (MgSO4). Two replicates were prepared, one with the cofactor and the one without. Since respiration produces carbon dioxide, the rate of cellular respiration could be measured through the volume of the gas evolved. Thus, the hypothesis “If enzymes need cofactors to speed up its function, cofactors affect the rate of cellular respiration.” was formulated. Substrates are molecules upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate(s). A hypothesis such as “If the nature of substrates affects the cellular respiration of yeast, then the simpler the substrates, the faster the cellular respiration.” was derived out of reasoning. The following were used as substrates for the experiments: (1) starch— a polysaccharide; (2) lactose—milk sugar; (3) sucrose—table sugar; (4) glucose—a monosaccharide; (5) fructose—fruit sugar; and (6) distilled water. The specific objectives of the study were 1. to cite means of measuring rate of cellular respiration specifically the anaerobic one; 2. to give some factors that affect cellular respiration; 3. to have hypotheses on these factors and test them using Durham and Smith tube methods; and 4. to conclude the effects of these factors MATERIALS AND METHODS In determining the effect of cofactors, two test tubes were obtained by one group. To these test tubes, the following were placed: test tube 1: 7 ml distilled water and 7 ml glucose, test tube 2: 7 ml glucose and 7ml 0.2 magnesium sulfate. Seven ml 10% yeast suspension was poured into each test tube and shaken vigorously. An inverted Durham tube was slide down into each of the test tubes as seen in Figure 2a. To remove air bubbles in the inverted Durham tube, the opening of the bigger test tube was covered tightly with the palm of one hand and the bubbles were let to escape from the said tube by tilting the bigger tube from side to side. Pasteur pipette was used to remove excess suspension that covers the tip of the inverted Durham tube. This was done to measure accurately the CO2 that will be trapped at the bottom of the inverted tube. The bigger tubes were plugged by cotton balls. Two replicates were performed by the same group. The height of the area occupied by the gas inside the inverted tube was measured after 30 minutes. The following formula was used. In Figure 6., the set-up with sucrose contained high volume of CO2 evolved as well with the glucose after 30 minutes. Figure 6. Smith fermentation set-up of sucrose and glucose after 30 minutes (L-R) In Figure 7., the set up with dh2o didn’t change while fructose yielded amount of carbon dioxide. Figure 7. Smith fermentation set-up of distilled water and fructose after 30 minutes (L-R) The results of the experiment attested the second working hypothesis which was “If the nature of substrates affects the cellular respiration of yeast, then the simpler the substrates, the faster the cellular respiration.” Comparing the nature of substrates, starch is the most complex because it is a polysaccharide followed by lactose and sucrose which are disaccharides; and glucose and fructose which are both monosaccharides only. Based on the results, sucrose produced the highest volume of co2 which could be accounted on the molecular formula of it. It was not required to be hydrolyzed compared to lactose, also a disaccharide, which produced zero carbon dioxide. Lactose, being a milk sugar, needed to be hydrolyzed to become effective substrates. In the experiment, lactose was not hydrolyzed so that it got zero co2; the same with water which is not a substrate for cellular respiration. Protein, fats and carbohydrates are the only substrates that could be used in cellular respiration. Glucose and fructose, being the simplest forms of sugar, were expected to give highest amount of the said gas. But, it did not happen. Sucrose is composed of two glucose sugars that is why it made a faster respiration rate. Therefore, with the stated conditions above, simpler the nature of the substrate is, the faster the rate of cellular respiration. SUMMARY AND CONCLUSION In experiment 1, the effect of cofactors on the rate of cellular respiration in yeast was determined by the Durham tube assembly. Mixtures of yeast with the substrate glucose was prepared in two replicates one with the cofactor Magnesium ion in the form of Magnesium sulfate and the one without. It was found that the mixture with the cofactor yielded more carbon dioxide. Since respiration produces carbon dioxide, the rate of cellular respiration could be measured through the volume of the gas evolved. Thus, the hypothesis “If enzymes need cofactors to speed up its function, cofactors affect the rate of cellular respiration.” was accepted. Cofactors assist the enzymes meaning speeding up cellular respiration Another experiment was performed to determine the effect of different substrates on the rate of cellular respiration using Smith fermentation tube assembly. Six substrates were used. They were the following with the volume of carbon dioxide they produced in cm3. Sucrose –34.35, fructose –33.84, glucose –31.81, starch –1.57, and both lactose and distilled water got zero. Some substrates have simple compositions and are easy to break down unlike while some have complex compositions and are hard to break down during the process of respiration. With the conditions that some sugars still need to be hydrolyzed, the hypothesis “If the nature of substrates affects the cellular respiration in yeast, then the simpler the substrates the faster the cellular respiration.” was still accepted. The simpler the substrates used, the faster the rate of cellular respiration. However, this must still need to be verified and justified by further experiments that would attest stronger to it. It is recommended that another experiment dealing with the nature of the substrates under the same procedure but with different microorganisms should be tried. LITERATURE CITED Campbell, N.A. and Bettelhein, A.D. 2007. Organic and BioChemistry. 6th ed. New York. Thomson Publishing Corporation. pp.89-95. Duka, I.M., Villa, N.O. and Diaz, M.G. 2009. Biology 1 Laboratory Manual: An investigative Approch. 9th ed. UPLB, IBS. GMBD. pp.51-55 Fogarty, W.M. and C.T. Kelly.1990. Microbial Enymes and Biotechnology. 2nd ed. London. Elsevier Science Publishers LTD. pp. 180-199. Lagunzad, L.M. and Padolina, M.C.D. 2003. Functional Biology. Philippines. Vibal Publishing House, Inc. pp. 277. Tsao, G.T. 1982. Annual Reports on Fermentation Processes. 5th Vol. Academic Press Inc. pp. 296. Vol’kenshtein, M.V. 1970. Molecules and Life. New York. Plenum Press Publishing Corporation. pp.30, 108.