National League for Nursing (NLN PAX) Practice Exam

The correct choice focuses on fermentation as the process primarily responsible for the breakdown of glucose in the absence of oxygen. Fermentation occurs when cells convert glucose into energy through a series of metabolic processes that do not require oxygen. This pathway is especially beneficial for organisms that thrive in anaerobic conditions or in environments where oxygen is limited.

During fermentation, glucose is typically converted into simpler compounds, such as lactic acid (in animals) or ethanol and carbon dioxide (in yeast and some bacteria), while producing a small amount of ATP. This allows cells to continue generating energy even when oxygen levels are insufficient.

Glycolysis, although it is a key initial stage in the breakdown of glucose, does not occur exclusively in the absence of oxygen. It is an anaerobic process that can take place regardless of oxygen availability, but it leads into further processes like fermentation or cellular respiration, depending on the oxygen environment.

Cellular respiration involves oxygen and includes processes that yield high amounts of ATP through aerobic pathways. Since this process requires oxygen, it is not relevant to the breakdown of glucose without oxygen.

Photosynthesis, on the other hand, is entirely different, as it involves converting light energy into chemical energy by synthesizing glucose from carbon dioxide and water, and it occurs in