what is the lactic acid fermentation?

Answer 1

Lactic acid fermentation is a form of anaerobic respiration. It occurs sometimes in muscle cells, when the circulation is not fast enough to bring enough oxygen for the contractions. Normally, during glycolysis, glucose is broken down to pyruvate, which enters the Krebs cycle, followed by oxidative phosphorylation. But in the absence of O2, pyruvate is converted to lactate in order to regenerate the reduced coenzymes (NADH). The energy (ATP) yield of this pathway is only 2 ATPs (isntead of 38 when oxygen is present).
The muscles after hard exercise are sour and painful because of the accumulated lactic acid.

Answer 2

Lactic acid fermentation is a form of anaerobic respiration that occurs in animal cells in the absence of oxygen. Glycolysis occurs normally, producing 2 molecules of ATP, 2 molecules of NADH and 2 molecules of pyruvate but the pyruvate is not metabolized to CO2 in the citric acid cycle. Furthermore, the electron transport chain (which uses O2) does not function. If the ATP needs of a cell outpace oxygen supply (such as during strenuous exercise), cells can only use fermentation for ATP production. Although it is a dead-end, the conversion of pyruvate to lactate regenerates NAD+ and this allows glycolysis to continue in the muscle cell. Lactate diffuses out of the cell and into the blood.

Certain cells, such as cardiac muscle cells, are highly permeable to lactate. Lactate is converted into pyruvate and metabolised normally (ie: via the citric acid cycle). Since these cells are highly oxygenated, it is unlikely that lactate would accumulate (as is the case in oxygen-starved muscle cells). This also allows circulating glucose to be available to muscle cells.

Any excess lactate is taken up by the liver, converted to pyruvate and then to glucose. This, along with the production of lactate from glucose in muscle cells constitutes the Cori cycle.

Phosphofructokinase (PFK) is inhibited by a low pH and this prevents the formation of excess lactate and/or lactic acidosis (sudden drop in blood pH). PFK catalyses an irreversible step in glycolysis.

Muscle cramps have been associated with levels of lactic acid in the blood, especially as a result of electrolyte imbalance caused by sweating. However, certain activities, which do not induce sweating or seem strenuous, still produce cramps (such as writing or playing an instrument) so it is unlikely that lactic acid is anything more than a minor factor.

Answer 3

Do you mean lactose fermentation?

Some bacteria have the ability to metabolize lactose ( a sugar ) and others do not. A rapid test in "MacConkey agar" is used, where an unknown bacterial colony is tested for lactose fermenting capability. When the bacteria are put in, they either break down the lactose, causing a color change, or they do not. This helps narrow down what type of bacteria are present.

Was that your question?