Grade: 10th B
Date 1: 09-02-2011
Date 2: 11-02-2011
In a general sense, fermentation is the conversion of a carbohydrate such as sugar into an acid or an alcohol. More specifically, fermentation can refer to the use of yeast to change sugar into alcohol or the use of bacteria to create lactic acid in certain foods. Fermentation occurs naturally in many different foods given the right conditions, and humans have intentionally made use of it for many thousands of years. Fermentation is important in anaerobic conditions when there is no oxidative phosphorylation to maintain the production of ATP by glycolysis. During fermentation, pyruvate is metabolised to various different compounds.
Homolactic fermentation is the production of lactic acid from pyruvate; alcoholic fermentation is the conversion of pyruvate into ethanol and carbon dioxide; and heterolactic fermentation is the production of ...view middle of the document...
This process is carried out by yeast and some bacteria cells using a range of enzymes. Alcoholic fermentation begins after glucose enters the cell. The glucose is broken down into pyruvic acid. This pyruvic acid is then converted to CO2, ethanol, and energy for the cell. This is in fact a complex series of conversions that brings about the conversion of sugar to CO2 and alcohol. These yeast cells gain energy from the conversion of the sugar into carbon dioxide and alcohol. The carbon dioxide by-product bubbles through the liquid and dissipates into the air. In limited spaces the carbon dioxide dissolves in the liquid making it fizzy. The pressure build up can be quite immense. The other by-product alcohol, remains in the liquid which is great for us but not for the yeast, as the yeast dies when the alcohol exceeds its tolerance level.
Lactic Fermentation is one of two anaerobic processes that can be used by a cell to create energy in the absence of oxygen. During lactic fermentation, the cell creates pyruvate through two steps. The first stage of this reaction is glycolysis, which is the one stage of cellular respiration that is common to all living organisms. During glycolysis the molecule glucose is broken into two molecules of pyruvate. The two molecules of NADH are oxidized and the hyrdogen molecules that are freed are used to reduce the two molecules of pyruvate which creates two molecules of lactate, also known as lactic acid .
Lactic Acid Fermentation has many important uses not only on a biological level, but on a utilitarian one as well. Because of the negative effects that it has on the body of mammals, alcoholic fermentation is not a possible means of producing energy within a cell when oxygen is not present. Also, if you have ever eaten cheese or yogurt, you have benefitted from lactic fermentation in another way. Both of these dairy products are created through lactic acid fermentation in various fungi and bacteria.