Which statement about glycolysis is true?

• A. It can be anaerobic or aerobic
• B. It requires oxygen as the final electron acceptor
• C. It occurs only in mitochondria
• D. It only occurs in plants

Answer: (A)

Glycolysis is the first step of glucose metabolism that occurs in the cytoplasm and does not require oxygen. It can proceed under both anaerobic and aerobic conditions. In the absence of oxygen, the NADH produced is reoxidized by fermentation, allowing glycolysis to continue and provide a quick ATP supply. When oxygen is present, the pyruvate produced can enter mitochondria for further energy extraction, but glycolysis itself does not depend on oxygen. It yields net ATP by substrate-level phosphorylation and produces NADH, without needing oxygen as the final electron acceptor. This pathway happens in virtually all cells, including plants and animals, and does not occur only in mitochondria.