Which molecule is released during the fermentation of grapes into ethanol?

Carbon dioxide(CO₂)

The correct answer is option 2. Carbon dioxide(CO₂).

During the fermentation of grapes into ethanol, the molecule released is Carbon dioxide (CO₂)

Fermentation: This is a biological process where microorganisms, such as yeast, convert sugars into cellular energy and other byproducts. In the case of grape fermentation, yeast breaks down the sugar glucose \((C_6H_{12}O_6) present in grapes.

Yeast Metabolism: Yeast utilizes a metabolic pathway called glycolysis to convert glucose into energy. This process does not require oxygen (anaerobic respiration).

Products of Glycolysis: As a result of glycolysis, glucose is broken down into two molecules of pyruvate \((CH_3COCOO^-)\) and releases energy in the form of ATP (adenosine triphosphate). Additionally, carbon dioxide \((CO_2)\) is released as a waste product.

Ethanol Production (Optional): Pyruvate can further be converted into ethanol \((C_2H_5OH)\) and another molecule of \(CO_2\) in a process called anaerobic fermentation. This step allows the yeast to regenerate NAD⁺, a crucial electron carrier needed for glycolysis.

Therefore, carbon dioxide \((CO_2)\) is the primary gaseous molecule released during the fermentation of grapes into ethanol.

Here is a breakdown of the other options:

Carbon monoxide \((CO)\): CO is not typically produced during fermentation. It's a product of incomplete combustion.

Water \((H_2O)\): While some water may be produced during fermentation, it's not the main gaseous product released.

None of the above: As explained earlier, \(CO_2\) is the key gaseous product of fermentation.