In aerobic respiration, where is water (H\(_2\)O) formed?

• A. During the Krebs cycle in the mitochondrial matrix
• B. During fermentation in the cytoplasm
• C. At the end of the electron transport chain in the mitochondria
• D. During glycolysis in the cytoplasm

Answer: (C)

Verified step by step guidance

1. Understand that aerobic respiration involves multiple stages: glycolysis, the Krebs cycle, and the electron transport chain (ETC). Each stage occurs in specific locations within the cell and has distinct functions.
2. Recall that the electron transport chain (ETC) is the final stage of aerobic respiration and occurs in the inner mitochondrial membrane. This is where most ATP is produced and where oxygen plays a critical role.
3. Recognize that oxygen acts as the final electron acceptor in the ETC. Electrons are passed along a series of protein complexes, and oxygen combines with electrons and protons (H\(^+\)) to form water (H\(_2\)O).
4. Note that water formation is a direct result of the reduction of oxygen at the end of the ETC. The chemical reaction can be represented as: O\(_2\) + 4H\(^+\) + 4e\(^-\) → 2H\(_2\)O.
5. Conclude that water is formed specifically at the end of the electron transport chain in the mitochondria, not during glycolysis, fermentation, or the Krebs cycle.