Question

End product of fermentation of sugar is-
A) Water and carbon dioxide
B) Alcohol and carbon dioxide
C) Carbon dioxide
D) Alcohol

Answer 1

Hint:Fermentation of carbohydrates is a metabolic process through which energy is extracted from carbohydrates in the absence of oxygen which results in production of alcohol while releasing carbon dioxide.

Complete answer:
Fermentation is a metabolic process where the action of enzymes changes chemical into organic substrates. It is defined as the energy extraction from carbohydrates in the absence of oxygen particularly in biochemistry. Ethanol fermentation or alcoholic fermentation is a biological process by which sugars such as glucose, fructose, and sucrose get converted into cellular energy, producing ethanol and carbon dioxide as by-products. As this process happens in absence of oxygen, alcoholic fermentation is called anaerobic fermentation. In this process, one mole of sugar gets converted into two moles of alcohol. The chemical process for alcoholic fermentation can be understood by following example-
\[{C_6}{H_{12}}{O_6} \to 2{C_2}{H_5}OH + 2C{O_2}\]
Sucrose is a sugar in which glucose is linked to a fructose. In the first step of alcoholic fermentation, the glycosidic linkage is cleaved by the enzyme invertase between the glucose and fructose molecules.
${C_2}{H_{22}}{O_{11}} + {H_2}O + Invertase \to 2{C_6}{H_{12}}{O_6}$
Each glucose molecule is then broken down into two pyruvate molecules by the process known as glycolysis:
\[{C_6}{H_{12}}{O_6} + 2ADP + 2Pi + 2NA{D^ + } \to 2C{H_3}COCO{O^ - } + 2ATP + 2NADH + 2{H_2}O + 2{H^ + }\]
Finally the pyruvate is converted to ethanol and carbon dioxide in two steps, regenerating oxidized NAD+ needed for glycolysis-
$C{H_3}CHO + NADH + {H^ + } \to {C_2}{H_5}OH + NA{D^ + }$ $C{H_3}COCO{O^ - } + {H^ + } \to C{H_3}CHO + C{O_2}$
Further catalysed by pyruvate decarboxylase-
 $C{H_3}CHO + NADH + {H^ + } \to {C_2}{H_5}OH + NA{D^ + }$

Thus, the correct answer is-” B”, Alcohol and carbon dioxide.

Note:Anaerobic fermentation occurs for sugars which forms carbon dioxide and alcohol, apart from this, lactic acid fermentation and acetic acid fermentation also occur.