In biochemistry and fermentation, which enzyme complex is responsible for converting glucose into ethyl alcohol (ethanol) during alcoholic fermentation by yeast?

Introduction / Context:
Alcoholic fermentation is a biological process in which sugars such as glucose are converted into ethyl alcohol (ethanol) and carbon dioxide by the action of enzymes in yeast. Several enzymes play roles in carbohydrate digestion and metabolism, but only one specific enzyme complex from yeast is traditionally associated with alcoholic fermentation. This question tests whether you can correctly identify zymase as the enzyme complex that converts glucose into ethanol during fermentation.

Given Data / Assumptions:
- The process discussed is the conversion of glucose into ethyl alcohol. - The context is alcoholic fermentation by yeast. - Options include the enzymes maltase, zymase, diastase, and invertase. - We assume standard textbook definitions and roles of these enzymes in carbohydrate metabolism.

Concept / Approach:
Zymase is the name given to the enzyme complex present in yeast that catalyses the series of reactions converting glucose to ethanol and carbon dioxide during fermentation. Maltase acts on maltose, diastase acts on starch, and invertase acts on sucrose. None of these other enzymes by themselves complete the fermentation pathway that produces ethanol. The correct approach is to match the specific function converting glucose to ethanol with zymase, rather than with enzymes that merely break down larger sugars into glucose or other monosaccharides.

Step-by-Step Solution:
Step 1: Recall the overall alcoholic fermentation reaction: glucose → ethanol + carbon dioxide, carried out anaerobically by yeast. Step 2: Recognise that zymase is the established name for the mixture of enzymes in yeast cells that catalyses this conversion. Step 3: Consider maltase. It hydrolyses maltose into two glucose molecules but does not by itself convert glucose into ethanol. Step 4: Consider diastase. It breaks down starch into maltose and smaller sugars but is not the fermenting enzyme complex producing ethanol. Step 5: Consider invertase. It splits sucrose into glucose and fructose; again, it prepares sugars for metabolism but does not complete the fermentation step to ethanol. Step 6: Therefore, among the options, the enzyme complex that actually performs alcoholic fermentation and produces ethyl alcohol is zymase.

Verification / Alternative check:
Biology and biochemistry textbooks describe the role of yeast in baking and brewing, emphasising that the zymase enzyme complex converts glucose into ethanol and carbon dioxide. Historically, zymase was one of the first enzyme complexes to be discovered and studied in the context of fermentation. While other enzymes like invertase and maltase help release glucose from larger carbohydrates, zymase is specifically linked with the final fermentation steps, confirming it as the correct choice.

Why Other Options Are Wrong:
Maltase (option a) only acts on maltose, not directly on glucose to produce ethanol. Diastase (option c) acts on starch, reducing it to smaller sugars such as maltose, but again does not complete the fermentation to alcohol. Invertase (option d) catalyses the hydrolysis of sucrose into glucose and fructose but stops there; the subsequent fermentation to ethanol requires zymase. Therefore, these enzymes play auxiliary roles in carbohydrate digestion or preparation but are not the main fermentation enzyme complex.

Common Pitfalls:
Students sometimes confuse the enzymes that prepare sugars (like invertase and diastase) with those that carry out fermentation itself. Another pitfall is to see the word malt in maltase and associate it with brewing, even though maltase only breaks maltose into glucose. To avoid such mistakes, remember that zymase is the classic name specifically linked to yeast fermentation of glucose into ethyl alcohol and carbon dioxide.

Final Answer:
The enzyme complex that converts glucose to ethyl alcohol during alcoholic fermentation is zymase.