Which of the following is NOT a product of the Krebs cycle?

The Krebs cycle, also known as the citric acid cycle or the tricarboxylic acid (TCA) cycle, is a central metabolic pathway that plays a crucial role in cellular respiration. This cycle processes acetyl-CoA to generate energy-rich molecules, which are essential for powering cellular functions.

Among the products generated during the Krebs cycle are ATP, NADH, and FADH2. ATP serves as a direct energy currency for the cell, while NADH and FADH2 act as electron carriers that transport electrons to the electron transport chain, where they will ultimately contribute to the production of additional ATP through oxidative phosphorylation.

In contrast, molecular oxygen (O2) is not produced during the Krebs cycle. Instead, oxygen is primarily utilized in the later stages of cellular respiration, particularly in the electron transport chain, where it functions as the final electron acceptor. Thus, identifying O2 as a product of the Krebs cycle is incorrect, as it is not generated within this cycle itself, but rather is essential for the completion of aerobic respiration elsewhere in the cell.