The Production of Pyruvate and Acetaldehyde During the Fermentation of Glucose.

Topics: Cellular respiration, Adenosine triphosphate, Glycolysis Pages: 7 (2333 words) Published: November 18, 2012
The glycolysis pathway is nearly universal in biological systems. Glycolysis is the sequence of reactions that converts glucose to pyruvate with the concomitant formation of ATP. Three fates of this pyruvate produced exist. In this practical the production of pyruvate and acetaldehyde by fermentation of glucose is established. A series of test tubes was set up each containing glucose and yeast suspension in buffers at different pH values. These test tubes were incubated for an hour at 37℃. Trichloro-acetic acid solution was then added to the first 2 of the 4 test tubes prior to centrifugation at 2500g. Solid ammonium sulphate and freshly prepared sodium nitroprusside were added to these tubes and colour observations made. For the remaining 2 tubes sodium nitroprusside and aqueous pyrrolidine were added to the supernatant and colour changes observed. INTRODUCTION/LIERATURE REVIEW

Three alternative catabolic routes are taken by the pyruvate formed by glycolysis. In aerobic organisms or tissues, under aerobic conditions, glycolysis constitutes only the first stage in the complete degradation of glucose. Pyruvate is oxidized, with loss of its carboxyl group as CO2, to yield the acetyl group of acetylcoenzyme A, which is then oxidized completely to CO2 by the citric acid cycle. The electrons from these oxidations are passed to O2 through a chain of carriers in the mitochondrion, forming H2O. (Voet and Voet; 2011). The energy from the electron transfer reactions drives the synthesis of ATP in the mitochondrion. The second route for pyruvate metabolism is its reduction to lactate via lactic acid fermentation. When a tissue such as vigorously contracting skeletal muscle must function anaerobically, the pyruvate cannot be oxidized further for lack of oxygen. Under these conditions pyruvate is reduced to lactate. Certain tissues and cell types (retina, brain, and erythrocytes) convert glucose to lactate even under aerobic conditions. Lactate (the dissociated form of lactic acid) is also the product of glycolysis under anaerobic conditions in microorganisms that carry out the lactic acid fermentation (www. The third major route for catabolism of pyruvate leads to ethanol. In some plant tissues and in certain invertebrates, protists, and microorganisms such as brewer's yeast, pyruvate is converted anaerobically into ethanol and CO2, a process called alcohol (or ethanol) fermentation. (Hames and Hopper; 2005) Pyruvate is an important metabolic intermediate in a variety of cellular processes that help create cellular energy. It is the simplest alpha-keto acid having the chemical formula CH3COCOO-. In humans, pyruvate is involved in converting sugar to energy, creating energy in the presence of oxygen, and even producing lactic acid, which occurs in muscle cells under low oxygen conditions. In other organisms, pyruvate is an intermediate in the fermentation of alcohol from glucose ( Pyruvate is a three-carbon molecule. One carbon atom exists as a methyl CH3 group, the middle carbon atom is double-bonded to an oxygen molecule, creating the ketone group, and the third carbon is part of a carboxyl COO- group. Pyruvate is the carboxylate anion of pyruvic acid, having the formula CH3COCOOH. (Wrolstad; et al; 2005). Glycolysis is the process by which cells convert sugar into energy. During glycolysis, the six-carbon sugar molecule called glucose is converted into two three-carbon pyruvate molecules through a series of steps. The process of glycolysis is not particularly efficient as a means of producing cellular energy. However, the resulting three-carbon pyruvate molecules are the beginning substrates needed to enter the citric acid cycle, which is a very efficient process of creating cellular energy. Pyruvate can also be converted into alcohol through the process of fermentation. In alcohol fermentation, two atoms of oxygen and one atom of carbon leave the pyruvate molecule...
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