Question

Define Glycolysis and Fermentation.

Answer 1

Respiration is a process that provides energy for carrying out activities. It is of two types, aerobic and anaerobic respiration which is solely based on the presence and absence of oxygen. This results in the release of energy in the form of ATP by the breakdown of glucose. In the case of anaerobic respiration, a certain process is accompanied by the formation of ethanol, lactic acid, etc.

Complete answer:
Glycolysis is defined as partial oxidation of the glucose to form two molecules of pyruvic acid. Glycolysis is derived from the word “glycon” for sugar and “lysis” for splitting simply means splitting up of sugar. The scheme of glycolysis was given by Gustav Embden, Otto Meyerhof, and J.Parnas, and is also known as EMP Pathway.
Fermentation is a kind of anaerobic respiration. It is mostly carried out primarily by fungi and bacteria. Gay Lussac was the first to discover fermentation.
Fermentation is mainly of two types:
-Alcoholic fermentation
-Lactic acid fermentation

Additional Information: - In plants, the glucose is derived from sucrose, which is the end product of photosynthesis, or from storage carbohydrates. Glucose and fructose are formed from the sucrose by the enzyme, invertase, and these two monosaccharides readily enter the glycolytic pathway. In animals, starch is digested into the glucose and that is used in the glycolysis.
The first half of this pathway activates glucose (glucose activation phase). The second half extracts the energy (energy extraction phase).
The net gain of ATP in this process is 2 ATP molecules and there is also the production of 2 molecules of ${ NADH }_{ 2 }$ .
In alcoholic fermentation, the pyruvic acid formed at the end of the glycolysis is converted to alcohol by using two enzymes, pyruvic acid decarboxylase, and alcohol dehydrogenase. This is commonly seen in yeast and bacteria. Yeast poison to death when the concentration of alcohol reaches about 13%.
In lactic acid fermentation, pyruvic acid formed at the end of glycolysis is reduced to lactic acid by homofermentative lactic acid bacteria.

Note: -The gaseous exchange, i.e., intake of oxygen and release of carbon dioxide is called breathing while respiration involves the biological oxidation of organic molecules i.e., breaking up of $C-C$ bonds by using enzymes and results in the release of energy in the form of ATP.
-It is the common step in both anaerobic and aerobic respiration as all organisms retain the machinery to partially oxidize glucose without the help of ${ O }_{ 2 }$.
-Since the glycolysis doesn’t require oxygen, it is the only process in respiration in anaerobic organisms.
-Both the process of fermentation is hazardous as either acid is produced or alcohol.
- During vigorous exercise, when the oxygen is inadequate for cellular respiration pyruvic acid is reduced to lactic acid by using enzyme lactate dehydrogenase.
- Alcohol fermentation results in the release of carbon dioxide with ethanol whereas lactic acid fermentation releases only lactic acid.