Final answer:
The purpose of sucrose in the fermentation experiment is as an energy source, and it is ultimately broken down into ethanol and carbon dioxide. This process is used in the production of bread, beer, and wine.
Step-by-step explanation:
The purpose of the sucrose in the fermentation experiment is to serve as an energy source for the yeast. During fermentation, sucrose is first broken down into glucose and fructose, and then microbes such as yeast break down the glucose to produce ethanol and carbon dioxide (CO2) as by-products, a process essential for making products like bread, beer, and wine. Hence, the correct answer to what sucrose is ultimately broken down into at the very end of fermentation is c) Sugar fermentation; ethanol and carbon dioxide.
In the lab investigation designed to measure the respiration of sugars by yeast, the sucrose provides a vital substrate for glycolysis, which is further fermented in the absence of oxygen. The gas pressure sensors in the experiments are used to measure CO2 production, quantitatively indicating the extent of fermentation taking place.