Final answer:
The enzymes involved in the preparation of ethanol from sucrose by fermentation are sucrase, which hydrolyzes sucrose into glucose and fructose, pyruvate decarboxylase, which converts pyruvate into acetaldehyde while releasing CO2, and alcohol dehydrogenase, which converts acetaldehyde into ethanol.
Step-by-step explanation:
The preparation of ethanol from sucrose by fermentation involves several enzymes and reactions. Initially, sucrose is hydrolyzed into glucose and fructose by the enzyme sucrase. Next, the glucose and fructose are fermented by yeast cells, specifically Saccharomyces cerevisiae, through two main reactions:
- The first reaction is catalyzed by the enzyme pyruvate decarboxylase which removes a carboxyl group from pyruvate (derived from glucose through glycolysis), releasing carbon dioxide (CO2) and forming acetaldehyde. This reaction requires a coenzyme derived from vitamin B1 (thiamine), known as thiamine pyrophosphate (TPP).
- The second reaction is catalyzed by alcohol dehydrogenase, which transfers an electron from NADH to acetaldehyde, producing ethanol and converting NADH back to NAD+.
The overall balanced chemical equation for the fermentation of glucose, which is part of the sucrose molecule, to ethanol and CO2 can be written as:
C6H12O6 → 2 C2H5OH + 2 CO2