Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What is the main process that leads to the production of ATP in cells during anaerobic conditions?

1. Fermentation

2. Photosynthesis

3. Aerobic respiration

4. Substrate-level phosphorylation

The correct answer is: Fermentation

The primary process that leads to the production of ATP in cells during anaerobic conditions is fermentation. In environments where oxygen is lacking, cells can still generate energy through this metabolic pathway. Fermentation allows for the conversion of glucose into ATP while producing byproducts such as lactic acid or ethanol, depending on the organism. This process includes glycolysis, which breaks down glucose to produce a small amount of ATP and is followed by fermentation pathways that regenerate NAD+, a crucial molecule for glycolysis to continue. Without oxygen, cells cannot efficiently produce ATP through aerobic respiration, which relies on the electron transport chain and requires oxygen as the final electron acceptor. Although substrate-level phosphorylation, which occurs during glycolysis and certain fermentation processes, does contribute to the ATP yield in anaerobic conditions, fermentation encompasses the entire process of energy production in the absence of oxygen, making it the more comprehensive answer in this context.