what is fermentation?

Answer 1

fermentation


process by which the living cell is able to obtain energy through the breakdown of glucose and other simple sugar molecules without requiring oxygen. Fermentation is achieved by somewhat different chemical sequences in different species of organisms. Two closely related paths of fermentation predominate for glucose. When muscle tissue receives sufficient oxygen supply, it fully metabolizes its fuel glucose to water and carbon dioxide. However, at times of strenuous activity, muscle tissue uses oxygen faster than the blood can supply it. During this anaerobic condition, the six-carbon glucose molecule is only partly broken down to two molecules of the three-carbon sugar called lactic acid. This process, called lactic acid fermentation, also occurs in many microorganisms and in the cells of most higher animals. In alcoholic fermentation, such as occurs in brewer's yeast and some bacteria, the production of lactic acid is bypassed, and the glucose molecule is degraded to two molecules of the two-carbon alcohol, ethanol, and to two molecules of carbon dioxide. Many of the enzymes of lactic acid and alcoholic fermentation are identical to the enzymes that bring about the metabolic conversion known as glycolysis. Alcoholic fermentation is a process that was known to antiquity. Before 2000 the Egyptians apparently knew that crushed fruits stored in a warm place would produce a substance with a pleasant intoxicating power. By 1500 the production of beer from germinating cereals (malt) and the preparation of wines from crushed grapes were established arts in most of the Middle East. Aristotle believed that grape juice was an infantile form of wine and that fermentation was, therefore, the maturation of the grape extract. Interest in the process of fermentation has continued through the ages, and much of modern biochemistry, especially enzyme studies, has emerged directly from early studies on the fermentation process. One of the earliest laboratories established for the study of biological chemistry was that founded in Copenhagen in 1875 and financed by the brewing family of Jacob Christian Jacobsen.

Answer 2

A biological reduction reaction where the product of glycolysis is reduced and NAD+ is regenerated in the absence of oxygen.

For yeasts:
Fermentation yields a two-carbon alcohol plus carbon dioxide from glucose, which has six carbons. Fermentation yields two two-carbon alcohol molecules (ethyl alcohol, or ethanol) plus two carbon dioxide molecules (2+2+1+1=6 Carbon). Fermentation is necessary for the regeneration of NAD+, which is previously converted to NADH in glycolysis. Basically, under anaerobic conditions (conditions with low or minimal oxygen) we produce ATP (the source of "energy") without oxygen, and NADH is produced. But if all NAD+ are converted to NADH. we run out of NAD+. Fermentation solves this problem by taking the NADH and reconverting it to NAD+. This is technically a reduction reaction because NADH donates "H".

For animals, fermentation is a little different, but NAD+ is still regenerated. Instead of breaking down the three-carbon molecule, it is simply converted to a three carbon lactate after reduction (addition of H). No carbon is lost in the form of carbon dioxide.

Here's a step-by-step example of fermentation in animals:

1. Glycolysis in the cytoplasm breaks down a six carbon sugar (like glucose) to two three-carbon pyruvate molecules, yielding NADH (which is a source of energy. 2 ATP are yielded per glucose from glycolysis). These 3C pyruvate, in the presence of oxygen, are further broken down until water and carbon dioxide are released in the mitochondria. But in the absence of oxygen, the pyruvate undergo a different chemical reaction directly in the cytoplasm.
2. Pyruvate in the cytoplasm is "fermented" (reduced) to lactate. Recall that no carbon dioxide is given off, unlike with alcoholic fermentation (where 2C alcohol and CO2 is produced- the CO2 explains why beer fizzes). As a result, NADH is recycled back into NAD+. This allows the process to continue.

In essence, all of this is about recycling NAD+ from NADH (or FADH+ from FADH2- which is similar).

Note: Some of the above answers discuss the "splitting" of a hydrocarbon molecule. This is not necessarily the case. Remember, glycolysis does the actual "splitting", a process that precedes fermentation. Those byproducts are then further reduced by addition of hydrogen. It is true that some organisms that ferment the byproduct of glycolysis release carbon dioxide, thus splitting a 3-carbon molecule into a 2-carbon ethanol and a 1-carbon carbon dioxide molecule. (This is the "classic" type of fermentation we have in yeasts). But for humans and other animals, fermentation does no splitting. The lactate by-product of pyruvate fermentation is likewise a 3-carbon molecule. (Luckily, we don't expel carbon dioxide from fermentation- could you imagine how nasty that would be?).

Answer 3

Fermentation is chemical changes in organic substances produced by the action of enzymes. This general definition includes virtually all chemical reactions of physiological importance, and scientists today often restrict the term to the action of specific enzymes, called ferments, produced by minute organisms such as molds, bacteria, and yeasts. For example, lactase, a ferment produced by bacteria usually found in milk, causes the milk to sour by changing lactose (milk sugar) into lactic acid. Probably the most important type of fermentation is alcoholic fermentation, in which the action of zymase secreted by yeast converts simple sugars, such as glucose and fructose, into ethyl alcohol and carbon dioxide. Many other kinds of fermentation occur naturally, as in the formation of butyric acid when butter becomes rancid and of acetic acid when wine turns to vinegar.

Generally, fermentation results in the breakdown of complex organic substances into simpler ones through the action of catalysis. For example, by the action of diastase, zymase, and invertase, starch is broken down (hydrolyzed) into complex sugars, then simple sugars, and finally alcohol.

Answer 4

I believe fermentation is when bacteria eats sugar and lets off a gas. It is helpful in beer or alcohol, but not in regular food.

Answer 5

Fermentation is the breakdown of monosaccharides(or simple sugars) into alcohol and carbon dioxide by the enzyme Zymase

Answer 6

Any of a group of chemical reactions induced by living or nonliving ferments that split complex organic compounds into relatively simple substances.

Answer 7

fermentation is chemical splitting of complex organic compunds into reletively simple substances i.e. the conversion or sugar to carbon dioxide and alcohol by yeast. used in preserving dead bodies and for making alcohol.

Answer 8

When yeasts digest sugars, alcohol results. The sugar can be naturally occurring (as in fruit). And thus grapes are turned into wine . . .

Answer 9

Sugars changing to to alcohol. Alcohol is a biproduct of yeast ingesting and digesting the sugars.

Answer 10

it is when a substance becomes alcohol..or something like that

http://en.wikipedia.org/wiki/Fermentation_%28food%29